如果您想了解死磕java集合之ConcurrentHashMap源码分析的相关知识，那么本文是一篇不可错过的文章，我们将对三进行全面详尽的解释，并且为您提供关于ConcurrentHashMap源码分
如果您想了解死磕 java集合之ConcurrentHashMap源码分析的相关知识，那么本文是一篇不可错过的文章，我们将对三进行全面详尽的解释，并且为您提供关于ConcurrentHashMap源码分析、ConcurrentHashMap源码分析-Java8、ConcurrentHashMap源码分析（JDK1.7）、ConcurrentHashMap源码分析（一）的有价值的信息。
本文目录一览：- 死磕 java集合之ConcurrentHashMap源码分析（三）（java集合源码解析）
- ConcurrentHashMap源码分析
- ConcurrentHashMap源码分析-Java8
- ConcurrentHashMap源码分析（JDK1.7）
- ConcurrentHashMap源码分析（一）
死磕 java集合之ConcurrentHashMap源码分析（三）（java集合源码解析）
本章接着上两章，链接直达：
死磕 java集合之ConcurrentHashMap源码分析（一）
死磕 java集合之ConcurrentHashMap源码分析（二）
删除元素
删除元素跟添加元素一样，都是先找到元素所在的桶，然后采用分段锁的思想锁住整个桶，再进行操作。
public V remove(Object key) {
// 调用替换节点方法
return replaceNode(key, null, null);
}
final V replaceNode(Object key, V value, Object cv) {
// 计算hash
int hash = spread(key.hashCode());
// 自旋
for (Node<K,V>[] tab = table;;) {
Node<K,V> f; int n, i, fh;
if (tab == null || (n = tab.length) == 0 ||
(f = tabAt(tab, i = (n - 1) & hash)) == null)
// 如果目标key所在的桶不存在，跳出循环返回null
break;
else if ((fh = f.hash) == MOVED)
// 如果正在扩容中，协助扩容
tab = helpTransfer(tab, f);
else {
V oldVal = null;
// 标记是否处理过
boolean validated = false;
synchronized (f) {
// 再次验证当前桶第一个元素是否被修改过
if (tabAt(tab, i) == f) {
if (fh >= 0) {
// fh>=0表示是链表节点
validated = true;
// 遍历链表寻找目标节点
for (Node<K,V> e = f, pred = null;;) {
K ek;
if (e.hash == hash &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
// 找到了目标节点
V ev = e.val;
// 检查目标节点旧value是否等于cv
if (cv == null || cv == ev ||
(ev != null && cv.equals(ev))) {
oldVal = ev;
if (value != null)
// 如果value不为空则替换旧值
e.val = value;
else if (pred != null)
// 如果前置节点不为空
// 删除当前节点
pred.next = e.next;
else
// 如果前置节点为空
// 说明是桶中第一个元素，删除之
setTabAt(tab, i, e.next);
}
break;
}
pred = e;
// 遍历到链表尾部还没找到元素，跳出循环
if ((e = e.next) == null)
break;
}
}
else if (f instanceof TreeBin) {
// 如果是树节点
validated = true;
TreeBin<K,V> t = (TreeBin<K,V>)f;
TreeNode<K,V> r, p;
// 遍历树找到了目标节点
if ((r = t.root) != null &&
(p = r.findTreeNode(hash, key, null)) != null) {
V pv = p.val;
// 检查目标节点旧value是否等于cv
if (cv == null || cv == pv ||
(pv != null && cv.equals(pv))) {
oldVal = pv;
if (value != null)
// 如果value不为空则替换旧值
p.val = value;
else if (t.removeTreeNode(p))
// 如果value为空则删除元素
// 如果删除后树的元素个数较少则退化成链表
// t.removeTreeNode(p)这个方法返回true表示删除节点后树的元素个数较少
setTabAt(tab, i, untreeify(t.first));
}
}
}
}
}
// 如果处理过，不管有没有找到元素都返回
if (validated) {
// 如果找到了元素，返回其旧值
if (oldVal != null) {
// 如果要替换的值为空，元素个数减1
if (value == null)
addCount(-1L, -1);
return oldVal;
}
break;
}
}
}
// 没找到元素返回空
return null;
}
（1）计算hash；
（2）如果所在的桶不存在，表示没有找到目标元素，返回；
（3）如果正在扩容，则协助扩容完成后再进行删除操作；
（4）如果是以链表形式存储的，则遍历整个链表查找元素，找到之后再删除；
（5）如果是以树形式存储的，则遍历树查找元素，找到之后再删除；
（6）如果是以树形式存储的，删除元素之后树较小，则退化成链表；
（7）如果确实删除了元素，则整个map元素个数减1，并返回旧值；
（8）如果没有删除元素，则返回null；
获取元素
获取元素，根据目标key所在桶的第一个元素的不同采用不同的方式获取元素，关键点在于find()方法的重写。
public V get(Object key) {
Node<K,V>[] tab; Node<K,V> e, p; int n, eh; K ek;
// 计算hash
int h = spread(key.hashCode());
// 如果元素所在的桶存在且里面有元素
if ((tab = table) != null && (n = tab.length) > 0 &&
(e = tabAt(tab, (n - 1) & h)) != null) {
// 如果第一个元素就是要找的元素，直接返回
if ((eh = e.hash) == h) {
if ((ek = e.key) == key || (ek != null && key.equals(ek)))
return e.val;
}
else if (eh < 0)
// hash小于0，说明是树或者正在扩容
// 使用find寻找元素，find的寻找方式依据Node的不同子类有不同的实现方式
return (p = e.find(h, key)) != null ? p.val : null;
// 遍历整个链表寻找元素
while ((e = e.next) != null) {
if (e.hash == h &&
((ek = e.key) == key || (ek != null && key.equals(ek))))
return e.val;
}
}
return null;
}
（1）hash到元素所在的桶；
（2）如果桶中第一个元素就是该找的元素，直接返回；
（3）如果是树或者正在迁移元素，则调用各自Node子类的find()方法寻找元素；
（4）如果是链表，遍历整个链表寻找元素；
（5）获取元素没有加锁；
获取元素个数
元素个数的存储也是采用分段的思想，获取元素个数时需要把所有段加起来。
public int size() {
// 调用sumCount()计算元素个数
long n = sumCount();
return ((n < 0L) ? 0 :
(n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE :
(int)n);
}
final long sumCount() {
// 计算CounterCell所有段及baseCount的数量之和
CounterCell[] as = counterCells; CounterCell a;
long sum = baseCount;
if (as != null) {
for (int i = 0; i < as.length; ++i) {
if ((a = as[i]) != null)
sum += a.value;
}
}
return sum;
}
（1）元素的个数依据不同的线程存在在不同的段里；（见addCounter()分析）
（2）计算CounterCell所有段及baseCount的数量之和；
（3）获取元素个数没有加锁；
总结
（1）ConcurrentHashMap是HashMap的线程安全版本；
（2）ConcurrentHashMap采用（数组 + 链表 + 红黑树）的结构存储元素；
（3）ConcurrentHashMap相比于同样线程安全的HashTable，效率要高很多；
（4）ConcurrentHashMap采用的锁有 synchronized，CAS，自旋锁，分段锁，volatile等；
（5）ConcurrentHashMap中没有threshold和loadFactor这两个字段，而是采用sizeCtl来控制；
（6）sizeCtl = -1，表示正在进行初始化；
（7）sizeCtl = 0，默认值，表示后续在真正初始化的时候使用默认容量；
（8）sizeCtl > 0，在初始化之前存储的是传入的容量，在初始化或扩容后存储的是下一次的扩容门槛；
（9）sizeCtl = (resizeStamp << 16) + (1 + nThreads)，表示正在进行扩容，高位存储扩容邮戳，低位存储扩容线程数加1；
（10）更新操作时如果正在进行扩容，当前线程协助扩容；
（11）更新操作会采用synchronized锁住当前桶的第一个元素，这是分段锁的思想；
（12）整个扩容过程都是通过CAS控制sizeCtl这个字段来进行的，这很关键；
（13）迁移完元素的桶会放置一个ForwardingNode节点，以标识该桶迁移完毕；
（14）元素个数的存储也是采用的分段思想，类似于LongAdder的实现；
（15）元素个数的更新会把不同的线程hash到不同的段上，减少资源争用；
（16）元素个数的更新如果还是出现多个线程同时更新一个段，则会扩容段（CounterCell）；
（17）获取元素个数是把所有的段（包括baseCount和CounterCell）相加起来得到的；
（18）查询操作是不会加锁的，所以ConcurrentHashMap不是强一致性的；
（19）ConcurrentHashMap中不能存储key或value为null的元素；
彩蛋——值得学习的技术
ConcurrentHashMap中有哪些值得学习的技术呢？
我认为有以下几点：
（1）CAS + 自旋，乐观锁的思想，减少线程上下文切换的时间；
（2）分段锁的思想，减少同一把锁争用带来的低效问题；
（3）CounterCell，分段存储元素个数，减少多线程同时更新一个字段带来的低效；
（4）@sun.misc.Contended（CounterCell上的注解），避免伪共享；（p.s.伪共享我们后面也会讲的^^）
（5）多线程协同进行扩容；
（6）你又学到了哪些呢？
彩蛋——不能解决的问题
ConcurrentHashMap不能解决什么问题呢？
请看下面的例子：
private static final Map<Integer, Integer> map = new ConcurrentHashMap<>();
public void unsafeUpdate(Integer key, Integer value) {
Integer oldValue = map.get(key);
if (oldValue == null) {
map.put(key, value);
}
}
这里如果有多个线程同时调用unsafeUpdate()这个方法，ConcurrentHashMap还能保证线程安全吗？
答案是不能。因为get()之后if之前可能有其它线程已经put()了这个元素，这时候再put()就把那个线程put()的元素覆盖了。
那怎么修改呢？
答案也很简单，使用putIfAbsent()方法，它会保证元素不存在时才插入元素，如下：
public void safeUpdate(Integer key, Integer value) {
map.putIfAbsent(key, value);
}
那么，如果上面oldValue不是跟null比较，而是跟一个特定的值比如1进行比较怎么办？也就是下面这样：
public void unsafeUpdate(Integer key, Integer value) {
Integer oldValue = map.get(key);
if (oldValue == 1) {
map.put(key, value);
}
}
这样的话就没办法使用putIfAbsent()方法了。
其实，ConcurrentHashMap还提供了另一个方法叫replace(K key, V oldValue, V newValue)可以解决这个问题。
replace(K key, V oldValue, V newValue)这个方法可不能乱用，如果传入的newValue是null，则会删除元素。
public void safeUpdate(Integer key, Integer value) {
map.replace(key, 1, value);
}
那么，如果if之后不是简单的put()操作，而是还有其它业务操作，之后才是put()，比如下面这样，这该怎么办呢？
public void unsafeUpdate(Integer key, Integer value) {
Integer oldValue = map.get(key);
if (oldValue == 1) {
System.out.println(System.currentTimeMillis());
/**
* 其它业务操作
*/
System.out.println(System.currentTimeMillis());
map.put(key, value);
}
}
这时候就没办法使用ConcurrentHashMap提供的方法了，只能业务自己来保证线程安全了，比如下面这样：
public void safeUpdate(Integer key, Integer value) {
synchronized (map) {
Integer oldValue = map.get(key);
if (oldValue == null) {
System.out.println(System.currentTimeMillis());
/**
* 其它业务操作
*/
System.out.println(System.currentTimeMillis());
map.put(key, value);
}
}
}
这样虽然不太友好，但是最起码能保证业务逻辑是正确的。
当然，这里使用ConcurrentHashMap的意义也就不大了，可以换成普通的HashMap了。
上面只是举一个简单的例子，我们不能听说ConcurrentHashMap是线程安全的，就认为它无论什么情况下都是线程安全的，还是那句话尽信书不如无书。
这也正是我们读源码的目的之一，了解其本质，才能在我们的实际工作中少挖坑，不论是挖给别人还是挖给自己^^。
ConcurrentHashMap源码分析
/** JDK7 */
public class ConcurrentHashMap<K, V> extends AbstractMap<K, V> implements ConcurrentMap<K, V>, Serializable {
private static final long serialVersionUID = 7249069246763182397L;
/**
* 默认的初始容量是16
*/
static final int DEFAULT_INITIAL_CAPACITY = 16;
/**
* 默认的加载因子是0.75
*/
static final float DEFAULT_LOAD_FACTOR = 0.75f;
/**
* 默认的并发级别是16
*/
static final int DEFAULT_CONCURRENCY_LEVEL = 16;
/**
* The maximum capacity, used if a higher value is implicitly specified by either of the constructors with arguments.
* MUST be a power of two <= 1<<30 to ensure that entries are indexable using ints.
*/
static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* The minimum capacity for per-segment tables.
* Must be a power of two, at least two to avoid immediate resizing on next use after lazy construction.
*/
static final int MIN_SEGMENT_TABLE_CAPACITY = 2;
/**
* The maximum number of segments to allow; used to bound constructor arguments.
* Must be power of two less than 1 << 24.
*/
static final int MAX_SEGMENTS = 1 << 16; // slightly conservative
/**
* Number of unsynchronized retries in size and containsValue methods before resorting to locking.
* This is used to avoid unbounded retries if tables undergo continuous modification which would make it impossible to obtain an accurate result.
*/
static final int RETRIES_BEFORE_LOCK = 2;
/**
* 在计算数组的下标时会用到该值：hashValue & segmentMask
*
* segmentMask = segments.length - 1
*/
final int segmentMask;
/**
* Shift value for indexing within segments.
*/
final int segmentShift;
/**
* Segment数组，Segment的功能类似于HashTable。
*
*/
final Segment<K,V>[] segments;
/**
* ConcurrentHashMap的构造函数
* 参数：
* initialCapacity： ConcurrentHashMap的初始容量
* loadFactor： Segment的加载因子(Segment数组是不可以扩容的，ConcurrentHashMap的扩容是通过Segment的扩容实现的)
* concurrencyLevel： 并发级别，默认为16，根据该参数计算出Segment数组的长度，Segment数组的长度必须是2的整数次幂，并且一旦设定，不可改变。
* eg：指定concurrencyLevel为17，则Segment数组的长度为32。
*
*/
@SuppressWarnings("unchecked")
public ConcurrentHashMap(int initialCapacity, float loadFactor, int concurrencyLevel) {
if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0) throw new IllegalArgumentException();
if (concurrencyLevel > MAX_SEGMENTS) concurrencyLevel = MAX_SEGMENTS;
// 根据concurrencyLevel参数计算出一个2的整数次幂的数，作为Segment数组的长度。
// Find power-of-two sizes best matching arguments
int sshift = 0; // 2的指数
int ssize = 1; // Segment数组的长度：ssize=2^sshift
while (ssize < concurrencyLevel) {
++sshift;
ssize <<= 1;
}
this.segmentShift = 32 - sshift;
this.segmentMask = ssize - 1;
// 确定Segment数组中第一个Segment(s0)的HashEntry数组的长度。
if (initialCapacity > MAXIMUM_CAPACITY) initialCapacity = MAXIMUM_CAPACITY;
int c = initialCapacity / ssize;
if (c * ssize < initialCapacity) ++c;
int cap = MIN_SEGMENT_TABLE_CAPACITY; // HashEntry数组的长度，最小为2(最小值设为2，是为了避免插入一个元素后，就开始扩容)
while (cap < c)
cap <<= 1;
// new一个Segment对象
Segment<K,V> s0 = new Segment<K,V>(loadFactor, (int)(cap * loadFactor), (HashEntry<K,V>[])new HashEntry[cap]);
// new一个的Segment数组，大小为ssize
Segment<K,V>[] ss = (Segment<K,V>[])new Segment[ssize];
// 将S0放到Segment数组的第一个位置。Segment数组中其它位置的Segment在调用put()方法时会被初始化。
UNSAFE.putOrderedObject(ss, SBASE, s0); // ordered write of segments[0]
this.segments = ss;
}
/**
* key和value都不能为null，否则报空指针异常。
*
*/
@SuppressWarnings("unchecked")
public V put(K key, V value) {
Segment<K,V> s;
if (value == null) throw new NullPointerException();
// 根据key计算出Segment数组的下标j，计算方法与HashMap获取数组下标的方法类似，都是使用 hashVale & (2^n-1)。
int hash = hash(key);
int j = (hash >>> segmentShift) & segmentMask; // segmentMask = Segment数组的长度-1，此处类似于HashMap中的：h & (length-1);
// 对segments[j]进行初始化
if ((s = (Segment<K,V>)UNSAFE.getObject(segments, (j << SSHIFT) + SBASE)) == null) // nonvolatile; recheck; in ensureSegment
s = ensureSegment(j);
// 将key-value放到segments[j]的HashEntry数组的特定位置上。
return s.put(key, hash, value, false);
}
/**
* Returns the segment for the given index, creating it and
* recording in segment table (via CAS) if not already present.
*
* [@param](https://my.oschina.net/u/2303379) k the index
* [@return](https://my.oschina.net/u/556800) the segment
*/
@SuppressWarnings("unchecked")
private Segment<K,V> ensureSegment(int k) {
final Segment<K,V>[] ss = this.segments;
long u = (k << SSHIFT) + SBASE; // raw offset
Segment<K,V> seg;
if ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u)) == null) {
Segment<K,V> proto = ss[0]; // Segment数组中的第一个Segment，即segments[0]
int cap = proto.table.length;
float lf = proto.loadFactor;
int threshold = (int)(cap * lf);
HashEntry<K,V>[] tab = (HashEntry<K,V>[])new HashEntry[cap];
if ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u)) == null) { // recheck
// 新建一个Segment对象
// 该对象的加载因子等于segments[0]的加载因子，该对象的HashEntry数组(table)的初始容量等于segments[0]的HashEntry数组(table)当前的容量。
// 注:此时，segments[0]可能已经扩容多次了。
Segment<K,V> s = new Segment<K,V>(lf, threshold, tab);
// 将新建的Segment对象添加到Segment数组(segments)指定的位置，通过循环和CAS来保证多线程环境下数据的安全
while ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u)) == null) {
if (UNSAFE.compareAndSwapObject(ss, u, null, seg = s))
break;
}
}
}
return seg;
}
/**
*
* Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.
*/
public V get(Object key) {
Segment<K,V> s; // manually integrate access methods to reduce overhead
HashEntry<K,V>[] tab;
int h = hash(key);
long u = (((h >>> segmentShift) & segmentMask) << SSHIFT) + SBASE;
if ((s = (Segment<K,V>)UNSAFE.getObjectVolatile(segments, u)) != null && (tab = s.table) != null) {
for (HashEntry<K,V> e = (HashEntry<K,V>) UNSAFE.getObjectVolatile(tab, ((long)(((tab.length - 1) & h)) << TSHIFT) + TBASE); e != null; e = e.next) {
K k;
if ((k = e.key) == key || (e.hash == h && key.equals(k)))
return e.value;
}
}
return null;
}
// ************************************************ 补充：jdk1.6中ConcurrentHashMap的get方法 ************************************************
/**
* jdk1.6中ConcurrentHashMap的get方法：
* 1)首先根据key获取对应的HashEntry，若找不到对应的HashEntry，则直接返回null。
* 2)若找到了对应的HashEntry，则以不加锁的方式获取value(即HashEntry.value)，若value!=null，则直接返回。
* 注：HashEntry的value属性是volatile的，故value!=null时可直接返回value。
* 3)若value==null，则以加锁的方式来获取value并返回。
* 注：HashEntry!=null,但是HashEntry.value==null的情况是由于发生了指令重排序造成的。
*/
public V get(Object key) {
int hash = hash(key.hashCode());
return segmentFor(hash).get(key, hash);
}
/**
* ConcurrentHashMap.Segment的get方法：采用乐观锁的方式来保证数据的同步。
*
* Note：这里需要考虑到并发的情景：
* put方法中新建一个HashEntry的语句：tab[index] = new HashEntry<K,V>(key, hash, first, value);
* 1)这行代码可以分解为如下的3个步骤：
* ①类的加载、连接(验证->准备->解析)。
* ②初始化对象。 注：初始化后，类的加载就完成了。
* ③将tab[index]指向刚分配的内存地址。 注：这一步和类的加载过程没有任何关系
* 2)其中的②和③可能会被重排序：
* a compiler happens to reorder a HashEntry initialization with its table assignment
* 分配对象的内存空间 --> 将tab[index]指向刚分配的内存地址(即给tab[index]赋值) --> 初始化对象(给HashEntry的key、hash、next、value赋值)。
* 3)如果另一个线程执行put方法时，tab[index]已经被赋值，HashEntry的key、hash也已经被赋值，但是value还没来的及赋值，此时当前正在执行get方法的线程很可能会遇到：
* e(即tab[index]) != null 且 e.hash == hash && key.equals(e.key) 且 e.value = null 的情况，
* 故获取到e.value后需要判断一下e.value是否为空，如果e.value为空，则需要加锁重新读取。
*/
V get(Object key, int hash) {
if (count != 0) { // read-volatile (transient volatile int count;)
HashEntry<K,V> e = getFirst(hash);
while (e != null) {
if (e.hash == hash && key.equals(e.key)) { // 若key.equals(e.key)，说明此时找到了该key对应的HashEntry
V v = e.value;
if (v != null) // 判断是否为空。
return v;
return readValueUnderLock(e); // recheck 加锁重读
}
e = e.next;
}
}
return null;
}
/**
* ConcurrentHashMap.Segment的readValueUnderLock方法
*
* 【Reads value field of an entry under lock. Called if value field ever appears to be null.
* This is possible only if a compiler happens to reorder a HashEntry initialization with its table assignment, which is legal under memory model but is not known to ever occur.】
*/
V readValueUnderLock(HashEntry<K,V> e) {
lock();
try {
return e.value;
} finally {
unlock();
}
}
/**
* segmentFor的get方法
*/
final Segment<K,V> segmentFor(int hash) {
return segments[(hash >>> segmentShift) & segmentMask];
}
/**
* ConcurrentHashMap list entry. Note that this is never exported out as a user-visible Map.Entry.
*
* Because the value field is volatile, not final, it is legal wrt the Java Memory Model for an unsynchronized reader to see null instead of initial value when read via a data race.
* Although a reordering leading to this is not likely to ever actually occur,
* the Segment.readValueUnderLock method is used as a backup in case a null (pre-initialized) value is ever seen in an unsynchronized access method.
*/
static final class HashEntry<K,V> {
final K key;
final int hash;
volatile V value; // value被volatile修饰：如果该HashEntry的value被其它线程修改了，volatile可以保证其它线程的get()方法获取到的value是最新的。
final HashEntry<K,V> next;
HashEntry(K key, int hash, HashEntry<K,V> next, V value) {
this.key = key;
this.hash = hash;
this.next = next;
this.value = value;
}
@SuppressWarnings("unchecked")
static final <K,V> HashEntry<K,V>[] newArray(int i) {
return new HashEntry[i];
}
}
// ************************************************ jdk1.6中ConcurrentHashMap的get方法 ************************************************
/**
* Segment类似一个HashTable
*
* Segments are specialized versions of hash tables.
* This subclasses from ReentrantLock opportunistically, just to simplify some locking and avoid separate construction.
*/
static final class Segment<K,V> extends ReentrantLock implements Serializable {
private static final long serialVersionUID = 2249069246763182397L;
/**
* The maximum number of times to tryLock in a prescan before possibly blocking on acquire in preparation for a locked segment operation.
* On multiprocessors, using a bounded number of retries maintains cache acquired while locating nodes.
*/
static final int MAX_SCAN_RETRIES =
Runtime.getRuntime().availableProcessors() > 1 ? 64 : 1;
/**
* entry数组，用来储存数据的
* The per-segment table. Elements are accessed via entryAt/setEntryAt providing volatile semantics.
*/
transient volatile HashEntry<K,V>[] table;
/**
* Segment中元素的数量
*
* The number of elements.
* Accessed only either within locks or among other volatile reads that maintain visibility.
*/
transient int count;
/**
* 对table的大小造成影响的操作(eg:put、remove)次数
*
* The total number of mutative operations in this segment.
* Even though this may overflows 32 bits, it provides sufficient accuracy for stability checks in CHM isEmpty() and size() methods.
* Accessed only either within locks or among other volatile reads that maintain visibility.
*/
transient int modCount;
/**
* Segment的阀值，threshold = capacity * loadFactor
*/
transient int threshold;
/**
* Segment的负载因子
*/
final float loadFactor;
Segment(float lf, int threshold, HashEntry<K,V>[] tab) {
this.loadFactor = lf;
this.threshold = threshold;
this.table = tab;
}
final V put(K key, int hash, V value, boolean onlyIfAbsent) {
// 获取Segment的独占锁，如果该key对应的node(HashEntry)存在，则node的值为null；如果node不存在，则new一个HashEntry并赋值给node。
HashEntry<K,V> node = tryLock() ? null : scanAndLockForPut(key, hash, value);
V oldValue;
try {
HashEntry<K,V>[] tab = table;
int index = (tab.length - 1) & hash;
HashEntry<K,V> first = entryAt(tab, index);
for (HashEntry<K,V> e = first;;) {
if (e != null) {
K k;
if ((k = e.key) == key ||
(e.hash == hash && key.equals(k))) {
oldValue = e.value;
if (!onlyIfAbsent) {
e.value = value;
++modCount;
}
break;
}
e = e.next;
} else {
if (node != null) // node!=null说明该key对应的HashEntry之前不存在，此时node为scanAndLockForPut()方法中new的那个HashEntry
node.setNext(first);
else // node=null 说明该key对应的HashEntry之前就存在，故这里new一个HashEntry并赋值给node。
node = new HashEntry<K,V>(hash, key, value, first);
int c = count + 1;
if (c > threshold && tab.length < MAXIMUM_CAPACITY) // 若Segment的容量达到阀值，则扩容。
rehash(node);
else
setEntryAt(tab, index, node); // 若Segment的容量未达到阀值，则将node添加到链表的头部。
++modCount;
count = c;
oldValue = null;
break;
}
}
} finally {
// 释放Segment的独占锁
unlock();
}
return oldValue;
}
/**
* 寻找该key对应的HashEntry，如果找到则返回null；如果没有找到，则new一个HashEntry并返回。
* 在该方法返回前，当前线程必定已经持有该Segment的锁了。
*
* Scans for a node containing given key while trying to acquire lock, creating and returning one if not found.
* Upon return, guarantees that lock is held.
*
* @return a new node if key not found, else null
*/
private HashEntry<K,V> scanAndLockForPut(K key, int hash, V value) {
HashEntry<K,V> first = entryForHash(this, hash); // 这里的this指当前的Segment
HashEntry<K,V> e = first;
HashEntry<K,V> node = null;
int retries = -1; // negative while locating node
while (!tryLock()) { // 循环tryLock()来确保获取到Segment的锁。
HashEntry<K,V> f; // to recheck first below
if (retries < 0) {
if (e == null) {
if (node == null) // speculatively create node
node = new HashEntry<K,V>(hash, key, value, null);
retries = 0;
}
else if (key.equals(e.key))
retries = 0;
else
e = e.next;
}
// 如果遍历的次数(retries)超过了MAX_SCAN_RETRIES(单核时值为1，多核时值为64)，则使用lock()方法阻塞式的获取锁。
else if (++retries > MAX_SCAN_RETRIES) {
lock();
break;
}
// 如果有新的元素被添加到该链表(HashEntry)的头部，则重新遍历
else if ((retries & 1) == 0 && (f = entryForHash(this, hash)) != first) {
e = first = f; // re-traverse if entry changed
retries = -1;
}
}
return node;
}
/**
* 扩容为之前的2倍。
* Doubles size of table and repacks entries, also adding the given node to new table
*/
@SuppressWarnings("unchecked")
private void rehash(HashEntry<K,V> node) {
/*
* Reclassify nodes in each list to new table. Because we
* Because we are using power-of-two expansion, the elements from each bin must either stay at same index, or move with a power of two offset.
* We eliminate unnecessary node
* creation by catching cases where old nodes can be
* reused because their next fields won''t change.
* Statistically, at the default threshold, only about
* one-sixth of them need cloning when a table
* doubles. The nodes they replace will be garbage
* collectable as soon as they are no longer referenced by
* any reader thread that may be in the midst of
* concurrently traversing table. Entry accesses use plain
* array indexing because they are followed by volatile
* table write.
*/
HashEntry<K,V>[] oldTable = table;
int oldCapacity = oldTable.length;
int newCapacity = oldCapacity << 1; // 扩容为之前的2倍
threshold = (int)(newCapacity * loadFactor);
HashEntry<K,V>[] newTable = (HashEntry<K,V>[]) new HashEntry[newCapacity];
int sizeMask = newCapacity - 1;
for (int i = 0; i < oldCapacity ; i++) {
HashEntry<K,V> e = oldTable[i];
if (e != null) {
HashEntry<K,V> next = e.next;
int idx = e.hash & sizeMask;
if (next == null) // 如果该链表上只有一个元素
newTable[idx] = e;
else { // Reuse consecutive sequence at same slot
HashEntry<K,V> lastRun = e;
int lastIdx = idx;
for (HashEntry<K,V> last = next; last != null; last = last.next) {
int k = last.hash & sizeMask;
if (k != lastIdx) {
lastIdx = k;
lastRun = last;
}
}
newTable[lastIdx] = lastRun;
// Clone remaining nodes
for (HashEntry<K,V> p = e; p != lastRun; p = p.next) {
V v = p.value;
int h = p.hash;
int k = h & sizeMask;
HashEntry<K,V> n = newTable[k];
newTable[k] = new HashEntry<K,V>(h, p.key, v, n);
}
}
}
}
int nodeIndex = node.hash & sizeMask; // add the new node
node.setNext(newTable[nodeIndex]);
newTable[nodeIndex] = node;
table = newTable;
}
/**
* Scans for a node containing the given key while trying to acquire lock for a remove or replace operation.
* Upon return, guarantees that lock is held.
* Note that we must lock even if the key is not found, to ensure sequential consistency of updates.
*/
private void scanAndLock(Object key, int hash) {
// similar to but simpler than scanAndLockForPut
HashEntry<K,V> first = entryForHash(this, hash);
HashEntry<K,V> e = first;
int retries = -1;
while (!tryLock()) {
HashEntry<K,V> f;
if (retries < 0) {
if (e == null || key.equals(e.key))
retries = 0;
else
e = e.next;
}
else if (++retries > MAX_SCAN_RETRIES) {
lock();
break;
}
else if ((retries & 1) == 0 &&
(f = entryForHash(this, hash)) != first) {
e = first = f;
retries = -1;
}
}
}
}
/**
*
* value被volatile修饰：如果该HashEntry的value被其它线程修改了，volatile可以保证其它线程的get()方法获取到的value是最新的。
*
* ConcurrentHashMap list entry.
*/
static final class HashEntry<K,V> {
final int hash;
final K key;
volatile V value;
volatile HashEntry<K,V> next;
HashEntry(int hash, K key, V value, HashEntry<K,V> next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
}
/**
* Sets next field with volatile write semantics. (See above
* about use of putOrderedObject.)
*/
final void setNext(HashEntry<K,V> n) {
UNSAFE.putOrderedObject(this, nextOffset, n);
}
// Unsafe mechanics
static final sun.misc.Unsafe UNSAFE;
static final long nextOffset;
static {
try {
UNSAFE = sun.misc.Unsafe.getUnsafe();
Class k = HashEntry.class;
nextOffset = UNSAFE.objectFieldOffset
(k.getDeclaredField("next"));
} catch (Exception e) {
throw new Error(e);
}
}
}
/**
*
* 首先以不加锁的方式获取3次(注:jdk6中是2次)，如果其中任意连续两次的modCounts相等，则直接返回，否则以加锁的方式重新获取并返回。
*
* Returns the number of key-value mappings in this map.
* If the map contains more than <tt>Integer.MAX_VALUE</tt> elements, returns Integer.MAX_VALUE.
*/
public int size() {
// Try a few times to get accurate count. On failure due to continuous async changes in table, resort to locking.
final Segment<K,V>[] segments = this.segments;
int size;
boolean overflow; // true if size overflows 32 bits
long sum; // sum of modCounts
long last = 0L; // 记录上一次的sum
int retries = -1; // 记录获取的次数(0表示第一次，1表示第二次，2表示第三次)。
try {
for (;;) {
// 如果获取的次数超过3次，则给segments数组中的所有Segment加锁。
if (retries++ == RETRIES_BEFORE_LOCK) { // RETRIES_BEFORE_LOCK=2
for (int j = 0; j < segments.length; ++j)
ensureSegment(j).lock();
}
sum = 0L;
size = 0;
overflow = false;
for (int j = 0; j < segments.length; ++j) {
Segment<K,V> seg = segmentAt(segments, j);
if (seg != null) {
sum += seg.modCount; // map的modCount等于所有Segment的modCount相加
int c = seg.count;
if (c < 0 || (size += c) < 0) // map的size等于所有Segment的count相加 即：size += c
overflow = true;
}
}
// 判断本次获取的modCounts和上一次获取的modCounts是否相等，如果相等，则跳出循环。
if (sum == last) break;
last = sum;
}
} finally {
// 如果获取的次数超过3次，给segments数组中的所有Segment解锁。
if (retries > RETRIES_BEFORE_LOCK) {
for (int j = 0; j < segments.length; ++j)
segmentAt(segments, j).unlock();
}
}
return overflow ? Integer.MAX_VALUE : size;
}
// ...
}
ConcurrentHashMap源码分析-Java8
<h4 id="1concurrenthashmap特性">1.ConcurrentHashMap特性
说明：因为ConcurrentHashMap单词太长，所以下面均适用CHM替代ConcurrentHashMap
- 同为线程安全集合，但CHM没有任何访问操作需要锁定全表。这也注定了CHM上的操作效率之高。
- 表访问需要volatile/atomic读，写和CAS.这通过使用内在函数(sun.misc.Unsafe）完成。
- 向一个空bin中插入节点是通过CAS完成的，其它的更新操作(insert，delete，update)都需要锁lock。
- 从JDK8开始，CHM使用CAS算法替代了Segment的概念，保证线程安全。
- 构成结构：bin数组＋链表＋红黑树 红黑树被包装在TreeBin内
- 扩容机制：2倍扩容
- 常量：
- 默认容量：16；
- 负载因子：0.75 说明：在构造函数中重写此值只会影响初始表的容量，而不会使用实际的浮点值。
- 链表转红黑树阈值：8
- 红黑树转链表阈值：6
- table转为红黑树阈值：64
- resize时的最小并行度：16(因为默认16个bin)
- CHM的key，value都不能为null
- 访问操作(get等)和更新操作(remove等)同时发生时，根据happens-before原则，更新操作先执行，读操作后执行，从而保证了检索操作获取的值一定是最新值。
- 聚合状态方法的结果包括：size，isEmpty，containsValue通常都是仅当map不在其它线程中进行并发更新时才有用。
- 批量操作可以接受一个并行阈值参数parallelismThreshold。
- 如果当前map的size预估值比给定的阈值小，则方法顺序执行。
- 如果给定阈值=Long.MAX_VALUE，则不会出现并行操作。
- 如果给定阈值=1，则会导致并行最大化，通过使用ForkJoinPool.commonPool()方法，对子任务分离。
- 并行操作通常比顺序操作快，但不能保证一定是这样。并行操作更慢的情况有：
- 如果并行计算的基础工作比计算本身更昂贵，那么小map上的并行操作可能比顺序形式执行更慢。
- 如果所有处理器都忙于执行不相关的任务，并行化可能无法实现太多的实际并行性。(无法形成流水线操作)
- 支持序列化，不支持浅拷贝
- 两个线程访问同一个bin中不同的元素的锁争用概率为：1 / (8 * #elements)
- TreeBins存在的意义：保护了我们免于因过度resize带来的最坏影响。
- 每一个bin中的元素到达新的bin后要么索引不变，要么产生2的次幂的位移。我们通过捕获旧节点可以重用的情况来消除不必要的节点创建。平均而言，当table进行resize时，只有1/6的节点需要进行clone。
- table进行resize时，其它线程可以加入协助resize的过程(这不是为了获取锁)，从而使得平均聚合等待时间变短。
- 在遇到转发节点时，遍历会移动到新table而无需重新访问节点
- 能够用TreeMap替代TreeBin？
- 不能。
- 原因：TreeBins的查询及与查询相关的操作都使用了一种特殊的比较形式。TreeBins中包含的元素可能在实现Comparable上的原则不一样，所以对于它们之间的比较，则无法调用Compareto()方法。为了解决这一问题，tree通过hash值对其排序。如果Comparable.compareto 可用的话，再用这个方法对元素排序。在查找节点时，如果元素不具有可比性或比较为0，则可能需要对此节点对左右孩子都进行查询。如果所有元素都不是可比较的并且具有相同的哈希值，则需要对全table进行扫描。
- TreeBins也需要额外的锁定机制。list更新过程中依旧可以进行遍历，但是红黑树在更新时却不能进行遍历，因为红黑树的调整可能会改变树的根节点，也可能改变各个节点之间的连接情况。
- TreeBins包含一个简单的读写锁定机制，依赖于主要的同步策略：
- 插入，删除的结构调整会调用lock机制；
- 如果在结构调整前有读操作，则必须读操作完成后，再进行结构的调整操作。遵循happes-before原则。
- 扩展AbstractMap，但这只是仅仅为了与这个类的以前版本兼容。
方法、域的分析
- hash值求法
- spread(int h)
- 哈希值＝(h ^ (h >>> 16)) & HASH_BITS;//消除异或结果的最高位影响
- h：key的hashcode
- 方法分析：hash值无符号右移16位原因：因为table使用的是2的整数次幂的掩码，仅在当前掩码之上的位上变化的散列集将会总是碰撞。(比如，Float键的集合在小table中保持连续的整数)所以我们应用一个转换，将高位的影响向下扩展。这是在速度，性能，分布上做的一个平衡。 因为许多常见的哈希集合已经合理分布(它们就不会在spread机制中受益)因为我们已经使用了红黑树对bin中的大量碰撞做了处理，因此我们只是以最简单的方式做一些移位，然后进行异或运算，以减少系统损失，并合并由于表边界而不会用于索引计算的最高位的影响(也就是&运算)。
- spread(int h)
- 扩容方法：
- tableSizefor(int c)
- c： c＝1.5*capaticy+1;
- 返回值：>=c的第一个2的整数次幂
- 方法分析： 如果c为2的整数次幂，则返回c; 如果c不是2的整数次幂，则返回第一个比c大的2的整数次幂; eg：c=16，则返回结果为16；c=30，则返回结果为32;
- tableSizefor(int c)
- 三个访问table的方法
- 方法说明：
- 都是属于volatile类型的方法，所以即使在resize的过程中，访问对table中的元素获取的结果也是正确的
- 对setTabAt()方法的调用总是发生在lock区域内，所以原则上不需要完整的volatile语义，但是目前的代码还是保守地选择了volatile方式。
- 方法
- static final Node tabAt(Node[] tab， int i)
- static final boolean casTabAt(Node[] tab， int i， Node c， Node v)
- static final void setTabAt(Node[] tab， int i， Node v)
- 方法说明：
- bin数组：transient volatile Node[] table;
- sizeCtl：用于控制table初始化和resize的一个变量。
- 值为负数：table正在初始化or正在resize
- sizeCtl=-1：正在初始化;
- sizeCtl=-(1+n)：当前有n个线程正在进行resize;
- 当table未初始化时，保存创建时使用的初始表大小，或默认为0。初始化后，保存下一个要调整table大小的元素计数值。
- 4个构造函数
- ConcurrentHashMap()
- ConcurrentHashMap(int initialCapacity)
- ConcurrentHashMap(Map
package sourcecode.analysis;
/**
* @Author: cxh
* @CreateTime: 18/4/3 16:29
* @ProjectName: JavaBaseTest
*/
import java.io.ObjectStreamField;
import java.io.Serializable;
import <a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.*;
import <a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.reflect.P<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>meterizedType;
import <a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.reflect.Type;
import java.util.AbstractMap;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>tor;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CountedCompleter;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.atomic.<a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a>;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.<a href="https://www.jb51.cc/tag/reentrantlock/" target="_blank">reentrantlock</a>;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.BinaryOperator;
import java.util.function.Consumer;
import java.util.function.DoubleBinaryOperator;
import java.util.function.Function;
import java.util.function.IntBinaryOperator;
import java.util.function.LongBinaryOperator;
import java.util.function.T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleBiFunction;
import java.util.function.T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction;
import java.util.function.ToIntBiFunction;
import java.util.function.ToIntFunction;
import java.util.function.ToLongBiFunction;
import java.util.function.ToLongFunction;
import java.util.stream.Stream;
/**
* Hashtable<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>高并发检索,同时<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>高并发更新.
* ConcurrentHashMap和Hashtable遵守相同的<a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>规范,并且包含与Hashtable每种<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>相对应的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>版本.
* 但是，尽管所有操作都是线程安全的，但检索操作并不需要锁定,并且没有任何访问操作需要锁定全表.
* 这个类可以在依赖线程安全性的程序中与Hashtable完全互操作，但不依赖于它的同步细节.
*
* 检索操作(<a href="https://www.jb51.cc/tag/baokuo/" target="_blank">包括</a>get)通常不会对表加锁,因此可能会和更新操作(如put,remove)同时发生.
* 检索反映了最近完成的更新操作的结果.更正式的说:对<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>key的value的更新操作和读操作遵守happens-before
* 原则,所以同时发生检索和更新操作时,更新操作先执行,读操作<a href="https://www.jb51.cc/tag/houzhixing/" target="_blank">后执行</a>,从而保证了检索操作<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>的值一定是最新线程
* 更新的值.
* 对整体操作(如putAll和clear),并发检索可能只会反映出一部分条目的插入和<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>.同样的,I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tors,Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tors
* 和Enumerations只是在一定程度上反映了哈希表的状态or反映的是从i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor/enumeration它们创建后哈希表的状态.
* 它们并不会抛出并发异常ConcurrentModificationException.但是，迭代器被设计为一次只能由<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>线程使用.
* 请记住，聚合状态<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>的结果<a href="https://www.jb51.cc/tag/baokuo/" target="_blank">包括</a>:size,isEmpty,containsValue通常都是仅当map不在其它线程中进行并发更新时才有用.
* 否则，这些<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>的结果反映了可能足以用于监视或估计目的的暂态，但不适用于程序控制。
*
* 当碰撞冲突很多时(如不同hash值的key通过取模运算后进入了相同的slot),table会<a href="https://www.jb51.cc/tag/zidong/" target="_blank">自动</a>扩容,* slot扩容后大小为原来的2倍(和扩容时0.75<a href="https://www.jb51.cc/tag/fuzai/" target="_blank">负载</a>因子阈值保持一致)
* 随着映射的<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>和<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>，这个平均值可能会有很大的变化，但是总的来说，针对散列表,这已经是在时间/空间上做了折衷.
* 但是，调整这个或任何其他类型的哈希表可能是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>相对较慢的操作.在可能的情况下，通过构造器<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>,指定initialCapacity
* 是比较好的方式.另外<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>可选的构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>参数loadFactor提供了另一种定制初始表容量的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>，通过指定要用于计算给定元素数
* 分配空间量的表密度来<a href="https://www.jb51.cc/tag/zidingyi/" target="_blank">自定义</a>初始表容量.此外，为了与此类的以前版本兼容，构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>可以选择指定预期的concurrencyLevel
* 作为内部大小调整的附加<a href="https://www.jb51.cc/tag/tishi/" target="_blank">提示</a>.
* 注意:如果很多key都用一样的hashcode,则哈希表的<a href="https://www.jb51.cc/tag/xingneng/" target="_blank">性能</a>一定会降低.为了减弱这种影响,当key是可比较的对象时(实现了
* Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble接口),则ConcurrentHashMap可以通过对key的排序来打破这种关系.
*
* ConcurrentHashMap的Set<a href="https://www.jb51.cc/tag/duixiangchuangjian/" target="_blank">对象创建</a>方式有:newKeySet(),newKeySet(int),* 如果所有的key都是有效的,且values都无效(or所有的value值都一样),则还有一种视图创建方式:keySet(Object).
*
* ConcurrentHashMap可以用作可伸缩频率map（直方图或多重集的一种形式）,这可以使用LongAdder作为value,* 通过co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent来初始化.比如:
* 向ConcurrentHashMap<String,LongAdder>类型的变量freqs<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a><a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>count,你可以使用lambda表达式如下:
* freqs.co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent(k -> new LongAdder()).increment();
*
* 此类及其视图和迭代器实现了Map和I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor接口的所有可选<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>。
*
* ConcurrentHashMap的key和value都不能为null,这一点和hashtable一致.
*
* ConcurrentHashMap<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>一组顺序操作和并行的批量操作,和大多数Stream<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>不同,该操作被设计为线程安全
* 且经常应用于即使由其他线程同时更新的映射;例如，在计算共享<a href="https://www.jb51.cc/tag/zhuce/" target="_blank">注册</a>表中值的快照<a href="https://www.jb51.cc/tag/zhaiyao/" target="_blank">摘要</a>时。
* 有3种操作,每一种有4种形式,接受<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>包含keys,values,Entries,(key,value)参数的<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>.
* 因为ConcurrentHashMap的元素没有以任何特定的方式排序，并且可能在不同的并行执行中以不同的顺序处理，
* 所以提供的<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>的正确性不应取决于任何排序,及在过程中可能会瞬时改变的对象or值;除了forEach<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,其它<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>在理想情况下,* 应该是不会改变ConcurrentHashMap的.
* Map.Entry上的块操作<a href="https://www.jb51.cc/tag/buzhichi/" target="_blank">不支持</a><a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>setValue().
*
* forEach:对每个元素执行给定操作.
*
* search:返回在每个元素上应用给定<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>的第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>可用的非null元素;找到后不再进行后续的<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>.
*
* reduce:计算每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>元素.
* 设计的reduce<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>不能依赖元素顺序
*
* 批量操作可以接受<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>并行阈值参数p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold.
* 如果当前map的size预估值比给定的阈值小,则<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>顺序执行.
* 所以,如果给定阈值=Long.MAX_VALUE,则不会出现并行操作.
* 如果给定阈值=1,则会导致并行最大化,通过使用ForkJoinPool.commonPool()<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,对子任务分离.
* 通常情况下，您最初会选择这些极端值中的<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>，然后衡量使用中间开销与吞吐量之<a href="https://www.jb51.cc/tag/jiande/" target="_blank">间的</a>值的<a href="https://www.jb51.cc/tag/xingneng/" target="_blank">性能</a>。
*
* 批量操作的并发<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>来自ConcurrentHashMap的并发<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>：
* 插入,更新操作happens-before访问操作.
* 任何批量操作的结果反映了这些每元素关系的组成(但是，除非以某种方式知道它是静止的，否则就整个map而言，不一定是原子的）
* 相反，因为映射中的键和值永远不会为null，所以null作为当前缺少任何结果的可靠原子指标。
* 为了保持这个<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>，null作为所有非标量约简操作的隐含基础。
* 对于double，long和int版本，base应该与其他任何值结合时返回其他值（更正式地说，它应该是减少的标识元素）。
* 最常见的reduce<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>接口有这些<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>;例如,用MAX_VALUE或0或作为计算和的初始值。
*
* 作为参数提供的<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>和转换<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>应该类似地返回null来指示无结果（<a href="https://www.jb51.cc/tag/zaizhe/" target="_blank">在这</a>种情况下，它不被使用）
* 在映射的reduce<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>接口中,这也使得变换能够用作过滤器，如果元素不能合并,则返回null.
* 在search或者reduce操作中使用它们前,您可以通过在“null意味着现在没有”规则下自己组合它们来创建复合转换和过滤。
*
* 接受和/或返回Entry参数的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>维护键值关联.注意可以使用AbstractMap.SimpleEntry(k,v)作为空白entry参数.
*
* 批量操作可能会突然完成,从而引发<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a><a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>抛出异常.
* 请记住:在处理这样的异常时，其他并发执行的<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>也可能引发异常，或者即使第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>异常没有发生，其它异常也可能发生。
*
* 并行操作通常比顺序操作快,但不能保证一定是这样.
* 并行操作更慢的情况有:
* 1.如果并行计算的基础工作比计算本身更昂贵，那么小map上的并行操作可能比顺序形式执行更慢。
* 2.如果所有处理器都忙于执行不相关的任务，并行化可能无法实现太多的实际并行性。(无法形成流水线操作)
*
* <a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>序列化,<a href="https://www.jb51.cc/tag/buzhichi/" target="_blank">不支持</a>浅拷贝
*
* @since 1.5
* @author Doug Lea
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m <K> the type of keys maintained by this map
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m <V> the type of mapped values
*/
public class ConcurrentHashMap<K,V> extends AbstractMap<K,V>
implements ConcurrentMap<K,V>,Serializable {
private static final long serialVersionUID = 7249069246763182397L;
/*
* 概述:
*
* 这个散列表的主要设计目标是保持并发可读性（通常<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>get（），但也<a href="https://www.jb51.cc/tag/baokuo/" target="_blank">包括</a>迭代器和相关<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>），
* 同时最小化更新争用。次要目标是保持空间消耗与java.util.HashMap大致相同或更好，并支
* 持多线程在空表上较高的初始插入速率。
*
* 该映射通常用作分箱（分段）散列表。每个键值映射都保存在<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点中。大多数节点是具有散列，
* 键，值和下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>字段的基本节点类的实例。但是，存在各种子类：TreeNodes排列在平衡树中，而不是列表。
* TreeBins拥有TreeNodes集合的根。转发节点在调整大小期间放置在bin的头部。 ReservationNodes用作占位符，
* 同时在co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent和其它相关的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>中中建立值.
* 类型TreeBin，ForwardingNode和ReservationNode不包含普通的key，value或hash值，并且在<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>期间很容易
* 区分，因为它们具有负散列字段和空键和值字段。 （这些特殊节点要么不常见，要么是暂时的，所以携带一些未使用的
* 字段的影响是微不足道的。）
*
*
* 在第一次插入时，table大小被惰性初始化为2的整数次幂。表中的每个bin通常包含<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点列表（通常，列表只有零个或
* <a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点）。表访问需要volatile/atomic读，写和CAS<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>锁。因为在不<a href="https://www.jb51.cc/tag/zengjia/" target="_blank">增加</a>指针的情况这些操作无法实现，
* 所以我们使用内在<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>(sun.misc.Unsafe）操作。
*
* 我们使用节点散列字段的顶部（符号）位来进行控制 -- 由于地址限制，它无论如何都是可用的。具有负散列字段的节点是
* 被特别处理的,或者map<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>中直接被忽略.
*
* 向<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>空bin中插入节点是通过CAS完成的.在大多数key/hash分布中,这是一种很常见的put操作.其它的更新操作
* (insert,delete,update)都需要锁lock.因为如果每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin都分配<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>单独的lock会比较浪费存储空间,所以改为使用bin列表的
* 第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点本身作为锁。对这些锁的锁定<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>依赖于内置的“同步”监视器。
*
* 但是，使用列表的第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点作为锁本身并不足以满足：当<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点被锁定时，任何更新都必须首先验证它在锁定之后仍然是第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点，
* 如果不是，则重试.因为新节点总是追加到列表尾部，所以一旦节点首先进入<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>容器，它将保持第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>直到被<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>或容器变为无效（在调整大小时）。
*
* 每个分区都有锁的主要缺点是:由同<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>锁保护的分区列表中的其他节点上的其他更新操作可能会被延迟,比如equals()和映射等相关的<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>执行时,* 会花费很长时间.然而，<a href="https://www.jb51.cc/tag/tongji/" target="_blank">统计</a>上，在<a href="https://www.jb51.cc/tag/suiji/" target="_blank">随机</a>哈希码下，这不是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>常见问题。理想情况下,给定size的调整阈值为0.75,bin中节点的频率遵循平均
* 约为0.5的泊松分布,尽管调整size大小时泊松分布方差很大.忽略方差，列表大小k的预期出现是（exp（-0.5）* pow（0.5，k）/ factorial（k））。
* 第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>值是：
* 0: 0.60653066
* 1: 0.30326533
* 2: 0.07581633
* 3: 0.01263606
* 4: 0.00157952
* 5: 0.00015795
* 6: 0.00001316
* 7: 0.00000094
* 8: 0.00000006
* 其它值:只要是在10,000,000范围内,都会小于1.
*
* 两个线程访问同<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin中不同的元素的锁争用概率为:1 / (8 * #elements)
*
* 实际中遇到的哈希码分布有时会明显偏离均匀<a href="https://www.jb51.cc/tag/suiji/" target="_blank">随机</a>性。这<a href="https://www.jb51.cc/tag/baokuo/" target="_blank">包括</a>N>(1 << 30)的情况，所以一些key必然会出现碰撞。
* 因此，我们使用<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>二级策略，该策略适用于bin中节点数超过阈值的情况。这些TreeBins使用平衡树来保存节点（一种特殊形式的红黑树），
* 将<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>时间限制在O（log N).TreeBin中的每个<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>步骤至少比常规列表中的<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>步骤慢两倍，但考虑到N不能超过（1 << 64）（在内存地址
* 用完之前）,所以<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>步骤,锁的持有时间等等,都会受到限制,从而<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>节点个数会控制在100个以内.TreeBin节点（TreeNodes）也保持与
* 常规节点相同的“下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>”遍历指针，所以可以以相同的方式在迭代器中遍历。
*
* 当table中元素个数超过百分比阈值（名义上为0.75，但请参见下文）时，会调整table的大小。
* 启动线程负责分配并设置替换数组,后续使用这个concurrentHashMap的其它线程在发现元素个数超过<a href="https://www.jb51.cc/tag/fuzai/" target="_blank">负载</a>因子规定大小时,都可以对table进行
* resize操作.TreeBins的使用保护了我们免于因过度resize带来的最坏影响.
* resize的过程是将旧table中的每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin都复制到新table的遍历复制过程.然而，线程要求在传输之前通过字段transferIndex传输小块索引，
* 从而减少争用。字段sizeCtl中的<a href="https://www.jb51.cc/tag/shengcheng/" target="_blank">生成</a>戳记确保重新定位不重叠。因为resize时,按照2的整数次幂进行扩容,所以每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin中的元素到达新的bin
* 后要么索引不变,要么产生2的次幂的位移.我们通过捕获旧节点可以重用的情况来消除不必要的节点创建，因为它们的下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>域不会改变.
* 平均而言,当tableresize时,只有1/6的节点需要进行clone.
* 被替换掉的节点只要不再被读线程引用,则会被GC回收.
* 元素都被转移到新table后,旧table的bin中只包含<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>转发节点(其hash域为MOVED),这一节点将新table作为它的key.在遇到转发节点时,查找
* 和更新操作会转到新table中重新执行.
*
* 每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin从旧table到新table的转移都需要<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>其bin的锁,这一过程中,可以阻止想要<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>这个bin的lock的线程进行等待.
* 但是其它线程可以加入协助resize的过程(这不是为了<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>锁),从而使得平均聚合等待时间变短.
* 转移还需要保证:无论是新table,还是旧table,只要是可访问的bin,都要保证其能进行遍历.
* 这部分是通过从最后<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin（table.length - 1）开始向第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>方向进行的。
* 在遇到转发节点时，遍历会移动到新table而无需重新访问节点。为了保证无序移动时也不跳过中间节点,在遍历期间首次遇到转发节点时会创建<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>
* 堆栈，以便在稍后处理当前table时保持其位置.对这些保存/恢复机制的需求相对较少，但是当遇到<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>转发节点时，通常会有更多的节点.
* 所以Traversers使用简单的缓存方案来避免创建这么多新的TableStack节点。
* 遍历方案也适用于部分遍历bin（通过<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>可选的Traverser构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>）来<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>分区聚合操作。
*
* 用到了表的延迟初始化
*
* 元素个数的count值由LongAdder来维护.通过对其特殊设置，避免使用LongAdder来访问导致创建多个CounterCell的隐式竞争检测.
* 计数器机制避免更新上的争用，但如果在并发访问期间读取频率太高，可能会遇到缓存抖动。为避免频繁读，仅在<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>到已拥有两个或更多节点的
* bin时尝试调整竞争大小。在统一的散列分布下，发生在阈值处的概率约为13％，这意味着只有大约1/8需要检查阈值（并且在调整大小之后，很少这
* 样做）。
*
* TreeBins的<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a>及与<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a>相关的操作都使用了一种特殊的比较形式(这也是为什么不能使用现有集合TreeMap的原因).TreeBins中包含的元素可能
* 在实现Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble上的原则不一样,所以对于它们之<a href="https://www.jb51.cc/tag/jiande/" target="_blank">间的</a>比较,则无法<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>Compar<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>()<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>.为了<a href="https://www.jb51.cc/tag/jiejue/" target="_blank">解决</a>这一问题,tree通过hash值对其排序.如果
* Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble.compar<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a> 可用的话,再用这个<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>对元素排序.在查找节点时，如果元素不具有可比性或比较为0,则可能需要对此节点对左右孩子
* 都进行<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a>.如果所有元素都不是可比较的并且具有相同的哈希值，则需要对全table进行扫描.
* 插入节点调整平衡时,为了保证总体有序,我们将类和identityHashCodes作为等同处理.
* 红黑树调整平衡的算法是对CLR算法的改进.
*
* TreeBins也需要额外的锁定机制。list更新过程中依旧可以进行遍历,但是红黑树在更新时却不能进行遍历,因为红黑树的调整可能会改变树的根节点,* 也可能改变各个节点之<a href="https://www.jb51.cc/tag/jiande/" target="_blank">间的</a>连接情况.TreeBins包含<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>简单的读写锁定机制，依赖于主要的同步策略：插入,<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>的结构调整会<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>lock机制;如果
* 在结构调整前有读操作,则必须读操作完成后,再进行结构的调整操作.由于只可能有<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>waiter,所以可以简单的使用<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>waiter域来阻止所有的写
* 操作.然后,读操作永远不需要被阻塞.如果保持根锁定，它们沿next指针遍历，直到锁定变为可用或列表遍历完为止.这类情况下并遍历不快，
* 但是可以最大限度地提高总预期吞吐量.
*
* 为了保持与以前的API和序列化兼容,这个类的版本引入了几个特别的<a href="https://www.jb51.cc/tag/neirong/" target="_blank">内容</a>:主要是:保留了构造器参数concurrencyLevel,但并未使用.
* 我们接受<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>loadFactor构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>参数，但只将它应用于初始表容量(这个参数的使用仅此一次).我们还声明了<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>未使用的“Segment”类，
* 它只在序列化时以最小的形式实例化。
*
* 另外，它扩展了AbstractMap,但这只是仅仅为了与这个类的以前版本兼容.
*
* ConcurrentHashMap<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>的组织顺序:
* 1.主要的静态声明+工具类
* 2.主要的public<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>
* 3.扩容<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,树,遍历器,批量操作.
*/
/* ---------------- 常量 -------------- */
/**
* table的最大容量.
* 为什么不是1<<32? 因为32位散列字段的前两位用于控制目的.
* 1<<30=1073741824
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
//<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认容量:16,和HashMap一样.
private static final int DEFAULT_CAPACITY = 16;
//数组最大长度,在toArray等相关<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>中用到
static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
//<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认并发级别,已经不再使用的字段,之所以还存在只是为了和之前的版本兼容.
private static final int DEFAULT_CONCURRENCY_LEVEL = 16;
//此表的加载因子。在构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>中重写此值只会影响初始表的容量,而不会使用实际的浮点值.
private static final float LOAD_FACTOR = 0.75f;
//<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>当前元素,bin中元素个数=8,则链表转为树
static final int TREEIFY_THRESHOLD = 8;
//bin中元素个数到达6个,则树转链表
static final int UNTREEIFY_THRESHOLD = 6;
//table转为树的阈值:64,此值最小为4*TREEIFY_THRESHOLD,显然,这里设定了64为初始值.
static final int MIN_TREEIFY_CAPACITY = 64;
//table扩容时,bin转移个数,最小为<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认的DEFAULT_CAPACITY=16.
//因为扩容时,可以多个线程同时操作,所以16个bin会被分配给多个的线程进行转移
private static final int MIN_TRANSFER_STRIDE = 16;
/**
* The number of bits used for generation stamp in sizeCtl.
* Must be at least 6 for 32bit arrays.
* 用来控制扩容,单线程进入的变量
* 32位数组时,最小值为6
*/
private static int RESIZE_STAMP_BITS = 16;
//resize时的线程最大个数
private static final int MAX_RESIZERS = (1 << (32 - RESIZE_STAMP_BITS)) - 1;
/**
* The bit shift for recording size stamp in sizeCtl.
* 用来控制扩容,单线程进入的变量
*/
private static final int RESIZE_STAMP_SHIFT = 32 - RESIZE_STAMP_BITS;
//节点hash域的编码
static final int MOVED = -1; // forwarding nodes的hash值
static final int TREEBIN = -2; // roots of trees的hash值
static final int RESERVED = -3; // transient reservations的hash值
static final int HASH_BITS = 0x7fffffff; // 正常散列节点的可用二进制位
//当前可用<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a><a href="https://www.jb51.cc/tag/shuliang/" target="_blank">数量</a>
static final int N<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a> = Runtime.getRuntime().availableProcessors();
//用于序列化兼容性
private static final ObjectStreamField[] serialPersistentFields = {
new ObjectStreamField("segments",Segment[].class),new ObjectStreamField("segmentMask",Integer.TYPE),new ObjectStreamField("segmentShift",Integer.TYPE)
};
/* ---------------- 节点 -------------- */
/**
* static内部类:最核心的内部类,包装了key-value条目.
* 特别注意:
* 1.<a href="https://www.jb51.cc/tag/buzhichi/" target="_blank">不支持</a>setValue<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>.
* 2.包含负数哈希值的node子类是特殊的,允许key和value为null.
* 3.ConcurrentHashMap不允许key和value为null
*/
static class Node<K,V> implements Map.Entry<K,V> {
final int hash;
final K key;
volatile V val;//比hashmap多了关键字volatile
volatile Node<K,V> next;//比hashmap多了关键字volatile
Node(int hash,K key,V val,Node<K,V> next) {
this.hash = hash;
this.key = key;
this.val = val;
this.next = next;
}
public final K getKey() { return key; }
public final V getValue() { return val; }
//entry的hash值=key和value的hash值求异或,和hashmap相同
public final int hashCode() { return key.hashCode() ^ val.hashCode(); }
public final String toString(){ return key + "=" + val; }
//本<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>不被<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>
public final V setValue(V value) {
throw new UnsupportedOperationException();
}
/**
* 检查步骤:
* 1.是Map.Entry类型
* 2.key和value都等价
*/
public final boolean equals(Object o) {
Object k,v,u; Map.Entry<?,?> e;
return ((o instanceof Map.Entry) &&
(k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
(v = e.getValue()) != null &&
(k == key || k.equals(key)) &&
(v == (u = val) || v.equals(u)));
}
//虚拟化<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>map.get（）;在子类中被覆盖。
Node<K,V> find(int h,Object k) {
Node<K,V> e = this;
if (k != null) {
do {
K ek;
if (e.hash == h &&
((ek = e.key) == k || (ek != null && k.equals(ek))))
return e;
} while ((e = e.next) != null);
}
return null;
}
}
/* ---------------- 静态工具 -------------- */
/**
* hash值无符号右移16位原因:
* 因为table使用的是2的整数次幂的掩码,仅在当前掩码之上的位上变化的散列集将会总是碰撞。(比如，Float键的集合在小table中保持连续的整数)
* 所以我们应用<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>转换，将高位的影响向下扩展。这是在速度,<a href="https://www.jb51.cc/tag/xingneng/" target="_blank">性能</a>,分布上做的<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>平衡.
* 因为许多常见的哈希集合已经合理分布(它们就不会在spread机制中受益)
* 因为我们已经使用了红黑树对bin中的大量碰撞做了处理,因此我们只是以最简单的方式做一些移位,然后进行异或运算，
* 以减少系统损失，并合并由于表边界而不会用于索引计算的最高位的影响(也就是&运算)。
*
*/
static final int spread(int h) {
return (h ^ (h >>> 16)) & HASH_BITS;//消除异或结果的最高位影响
}
/**
* 如果c为2的整数次幂,则返回c;
* 如果c不是2的整数次幂,则返回第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>比c大的2的整数次幂;
* eg:c=16,则返回结果为16;
* c=30,则返回结果为32;
*/
private static final int tableSi<a href="https://www.jb51.cc/tag/zef/" target="_blank">zef</a>or(int c) {
int n = c - 1;
n |= n >>> 1;
n |= n >>> 2;
n |= n >>> 4;
n |= n >>> 8;
n |= n >>> 16;
return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
}
//如果传入参数x实现了Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble接口,则返回类x,否则返回null.同HashMap
static Class<?> comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bleClassFor(Object x) {
if (x instanceof <a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble) {
Class<?> c; Type[] ts,as; Type t; P<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>meterizedType p;
if ((c = x.getClass()) == String.class) // bypass checks
return c;
if ((ts = c.getGenericInterfaces()) != null) {
for (int i = 0; i < ts.length; ++i) {
if (((t = ts[i]) instanceof P<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>meterizedType) &&
((p = (P<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>meterizedType)t).getRawType() ==
<a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble.class) &&
(as = p.getActualTypeArguments()) != null &&
as.length == 1 && as[0] == c) // type arg is c
return c;
}
}
}
return null;
}
//如果x和kc类型相同,则返回k.compar<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>(x)结果;否则返回0.同HashMap
@SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble
static int compareComp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bles(Class<?> kc,Object k,Object x) {
return (x == null || x.getClass() != kc ? 0 :
((<a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble)k).compar<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>(x));
}
/* ---------------- 访问table元素<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a> -------------- */
/*
* 下面3个<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,都是属于volatile类型的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,所以即使在resize的过程中,访问对table中的元素<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>的结果也是正确的.
* 针对tab参数,必须有非null判定.然后判定tab的长度是否>0,最后判定索引i是否合法.
* 注意:为了纠正<a href="https://www.jb51.cc/tag/yonghu/" target="_blank">用户</a>发生的任意并发<a href="https://www.jb51.cc/tag/cuowu/" target="_blank">错误</a>，这些检查必须对局部变量进行操作，这些检查必须对本地变量进行操作，这些变量占了下面一些特别的内联分配。
* 注意:对setTabAt()<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>的<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>总是发生在lock区域内,所以原则上不需要完整的volatile语义,但是目前的<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>还是保守地选择了volatile方式.
*/
@SuppressWarnings("unchecked")
static final <K,V> Node<K,V> tabAt(Node<K,V>[] tab,int i) {
return (Node<K,V>)U.g<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>bjectVolatile(tab,((long)i << ASHIFT) + ABASE);
}
static final <K,V> boolean casTabAt(Node<K,int i,V> c,V> v) {
return U.compareAndSwapObject(tab,((long)i << ASHIFT) + ABASE,c,v);
}
static final <K,V> void setTabAt(Node<K,V> v) {
U.putObjectVolatile(tab,v);
}
/* ---------------- 域 -------------- */
/**
* bin数组
* 延迟初始化到第一次插入元素.
* 数组长度总是2的整数次幂.
* 可以通过迭代器进行访问.
*/
transient volatile Node<K,V>[] table;
//resize时用到的临时table,只有在resize时,才不为null
private transient volatile Node<K,V>[] nextTable;
//基本计数器值，主要用于没有争用时，也可作为表初始化期<a href="https://www.jb51.cc/tag/jiande/" target="_blank">间的</a>后备。通过CAS更新。
private transient volatile long baseCount;
/**
* 用于控制table初始化和resize的<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>变量.
* 值为负数:table正在初始化or正在resize
* sizeCtl=-1:正在初始化;
* sizeCtl=-(1+n):当前有n个线程<a href="https://www.jb51.cc/tag/zhengzaijinxing/" target="_blank">正在进行</a>resize;
* 当table未初始化时，保存创建时使用的初始表大小，或<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认为0。初始化后，保存下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>要调整table大小的元素计数值。
*/
private transient volatile int sizeCtl;
//resize时,next table的索引+1,用于分割.
//nexttable索引[0,2*n-1],故transferIndex=n
private transient volatile int transferIndex;
//在调整大小和/或创建CounterCells时使用的自旋锁（通过CAS锁定）。
private transient volatile int cellsBusy;
//这是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>计数器数组,用于保存每个bin中节点个数.
private transient volatile CounterCell[] counterCells;
//视图views
private transient KeySetView<K,V> keySet;
private transient ValuesView<K,V> values;
private transient EntrySetView<K,V> entrySet;
/* ---------------- Public操作 -------------- */
/*-------------4个构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>-----------*/
//table<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认大小16
public ConcurrentHashMap() {
}
//初始化容量为:>=1.5*initialCapacity+1的最小2的整数次幂
public ConcurrentHashMap(int initialCapacity) {
if (initialCapacity < 0)
throw new IllegalArgumentException();
int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ?
MAXIMUM_CAPACITY :
tableSi<a href="https://www.jb51.cc/tag/zef/" target="_blank">zef</a>or(initialCapacity + (initialCapacity >>> 1) + 1));
this.sizeCtl = cap;
}
//创建<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>和输入参数map映射一样的map
public ConcurrentHashMap(Map<? extends K,? extends V> m) {
this.sizeCtl = DEFAULT_CAPACITY;
putAll(m);
}
public ConcurrentHashMap(int initialCapacity,float loadFactor) {
this(initialCapacity,loadFactor,1);
}
public ConcurrentHashMap(int initialCapacity,float loadFactor,int concurrencyLevel) {
if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0)
throw new Ille<a href="https://www.jb51.cc/tag/gal/" target="_blank">gal</a>ArgumentException();
if (initialCapacity < concurrencyLevel) // Use at least as many bins
initialCapacity = concurrencyLevel; // as estimated threads
long size = (long)(1.0 + (long)initialCapacity / loadFactor);
//如果initialCapacity=16,则cap=32;
int cap = (size >= (long)MAXIMUM_CAPACITY) ?
MAXIMUM_CAPACITY : tableSi<a href="https://www.jb51.cc/tag/zef/" target="_blank">zef</a>or((int)size);
this.sizeCtl = cap;
}
// Original (since JDK1.2) Map methods
public int size() {
//节点总数n
long n = sumCount();
return ((n < 0L) ? 0 :
(n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE :
(int)n);
}
public boolean isEmpty() {
return sumCount() <= 0L; // ig<a href="https://www.jb51.cc/tag/nor/" target="_blank">nor</a>e transient negative values
}
public V get(Object key) {
Node<K,V>[] tab; Node<K,V> e,p; int n,eh; K ek;
//根据hash值查找散列位置
int h = spread(key.hashCode());
if ((tab = table) != null && (n = tab.length) > 0 &&
(e = tabAt(tab,(n - 1) & h)) != null) {
//如果tab[(n-1)&h]处的节点就是要查找的节点
if ((eh = e.hash) == h) {
if ((ek = e.key) == key || (ek != null && key.equals(ek)))
return e.val;
}
//如果是树节点
else if (eh < 0)
return (p = e.find(h,key)) != null ? p.val : null;
//如果是链表节点
while ((e = e.next) != null) {
if (e.hash == h &&
((ek = e.key) == key || (ek != null && key.equals(ek))))
return e.val;
}
}
return null;
}
//<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>上面的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>
public boolean containsKey(Object key) {
return get(key) != null;
}
public boolean containsValue(Object value) {
if (value == null)
throw new NullPointerException();
Node<K,V>[] t;
if ((t = table) != null) {
Traverser<K,V> it = new Traverser<K,V>(t,t.length,t.length);
for (Node<K,V> p; (p = it.advance()) != null; ) {
V v;
if ((v = p.val) == value || (v != null && value.equals(v)))
return true;
}
}
return false;
}
//key,value不能为null
public V put(K key,V value) {
return putVal(key,value,false);
}
/** Implementation for put and putIfAbsent
* 总体步骤:
* 1.判定key,value合法性
* 2.插入位置为空bin
* 3.插入位置<a href="https://www.jb51.cc/tag/zhengzaijinxing/" target="_blank">正在进行</a>resize
* 4.插入位置在table中,且该位置未进行resize
* 5.插入完成后,判定bin中节点个数是否>=8,从而决定是否进行链表转红黑树.
*
*/
final V putVal(K key,V value,boolean onlyIfAbsent) {
if (key == null || value == null) throw new NullPointerException();
//<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>hash值
int hash = spread(key.hashCode());
int binCount = 0;
for (Node<K,V>[] tab = table;;) {
Node<K,V> f; int n,i,fh;
if (tab == null || (n = tab.length) == 0)
tab = initTable();
//如果插入位置为空的bin
else if ((f = tabAt(tab,i = (n - 1) & hash)) == null) {
if (casTabAt(tab,null,new Node<K,V>(hash,key,null)))
break; // no lock when adding to empty bin
}
//如果查找位置为forwarding node
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
//在当前table中查找插入位置
else {
V oldVal = null;
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块,保证插入安全
synchronized (f) {
if (tabAt(tab,i) == f) {
//如果为链表
if (fh >= 0) {
binCount = 1;
for (Node<K,V> e = f;; ++binCount) {
K ek;
//找到,更新值
if (e.hash == hash &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
oldVal = e.val;
if (!onlyIfAbsent)
e.val = value;
break;
}
Node<K,V> pred = e;
if ((e = e.next) == null) {
pred.next = new Node<K,null);
break;
}
}
}
//如果为红黑树
else if (f instanceof TreeBin) {
Node<K,V> p;
binCount = 2;
if ((p = ((TreeBin<K,V>)f).putTreeVal(hash,value)) != null) {
oldVal = p.val;
if (!onlyIfAbsent)
p.val = value;
}
}
}
}
//插入节点后,检查bin中节点个数是否>=8,如果大于,则由链表转为红黑树
if (binCount != 0) {
if (binCount >= TREEIFY_THRESHOLD)
treeifyBin(tab,i);
if (oldVal != null)
return oldVal;
break;
}
}
}
addCount(1L,binCount);
return null;
}
public void putAll(Map<? extends K,? extends V> m) {
//对table的size进行设置,使得其可以容纳新加入的元素.
tryPresize(m.size());
for (Map.Entry<? extends K,? extends V> e : m.entrySet())
putVal(e.getKey(),e.getValue(),false);
}
public V remove(Object key) {
return replaceNode(key,null);
}
//此<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>是对4个公有<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>remove/replace的辅助<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>.
final V replaceNode(Object key,Object cv) {
int hash = spread(key.hashCode());
for (Node<K,fh;
//空表or查找位置bin为null
if (tab == null || (n = tab.length) == 0 ||
(f = tabAt(tab,i = (n - 1) & hash)) == null)
break;
//如果查找节点为转移节点forwarding node
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
else {
V oldVal = null;
boolean validated = false;
//同步代码块,保证删除安全性
synchronized (f) {
if (tabAt(tab,i) == f) {
//bin为链表结构
if (fh >= 0) {
validated = true;
for (Node<K,V> e = f,pred = null;;) {
K ek;
if (e.hash == hash &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
V ev = e.val;
if (cv == null || cv == ev ||
(ev != null && cv.equals(ev))) {
oldVal = ev;
if (value != null)
e.val = value;
else if (pred != null)
pred.next = e.next;
else
setTabAt(tab,e.next);
}
break;
}
//记录上<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>访问节点
pred = e;
//更新e为下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点
if ((e = e.next) == null)
break;
}
}
//bin为红黑树结构
else if (f instanceof TreeBin) {
validated = true;
TreeBin<K,V> t = (TreeBin<K,V>)f;
TreeNode<K,V> r,p;
if ((r = t.root) != null &&
(p = r.findTreeNode(hash,null)) != null) {
V pv = p.val;
if (cv == null || cv == pv ||
(pv != null && cv.equals(pv))) {
oldVal = pv;
if (value != null)
p.val = value;
else if (t.removeTreeNode(p))
setTabAt(tab,untreeify(t.f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t));
}
}
}
}
}
if (validated) {
if (oldVal != null) {
if (value == null)
//更新节点个数
addCount(-1L,-1);
return oldVal;
}
break;
}
}
}
return null;
}
public void clear() {
long delta = 0L; // negative number of deletions
int i = 0;
Node<K,V>[] tab = table;
while (tab != null && i < tab.length) {
int fh;
Node<K,V> f = tabAt(tab,i);
if (f == null)
++i;
//如果节点为转移节点forwarding node
else if ((fh = f.hash) == MOVED) {
tab = helpTransfer(tab,f);
i = 0; // restart
}
else {
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块,<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>i位置处的节点
synchronized (f) {
if (tabAt(tab,i) == f) {
Node<K,V> p = (fh >= 0 ? f :
(f instanceof TreeBin) ?
((TreeBin<K,V>)f).f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t : null);
while (p != null) {
--delta;
p = p.next;
}
setTabAt(tab,i++,null);
}
}
}
}
if (delta != 0L)
addCount(delta,-1);
}
public KeySetView<K,V> keySet() {
KeySetView<K,V> ks;
return (ks = keySet) != null ? ks : (keySet = new KeySetView<K,V>(this,null));
}
public Collection<V> values() {
ValuesView<K,V> vs;
return (vs = values) != null ? vs : (values = new ValuesView<K,V>(this));
}
public Set<Map.Entry<K,V>> entrySet() {
EntrySetView<K,V> es;
return (es = entrySet) != null ? es : (entrySet = new EntrySetView<K,V>(this));
}
//返回map的hash值.
//结果=sum(key.hashCode() ^ value.hashCode())
public int hashCode() {
int h = 0;
Node<K,V> p; (p = it.advance()) != null; )
h += p.key.hashCode() ^ p.val.hashCode();
}
return h;
}
//格式:{key1=value1,key2=value2,...}
public String toString() {
Node<K,V>[] t;
int f = (t = table) == null ? 0 : t.length;
Traverser<K,f,f);
StringBuilder sb = new StringBuilder();
sb.append('{');
Node<K,V> p;
if ((p = it.advance()) != null) {
for (;;) {
K k = p.key;
V v = p.val;
sb.append(k == this ? "(this Map)" : k);
sb.append('=');
sb.append(v == this ? "(this Map)" : v);
if ((p = it.advance()) == null)
break;
sb.append(',').append(' ');
}
}
return sb.append('}').toString();
}
/**
* Compares the specified object with this map for equality.
* Returns {@code true} if the given object is a map with the same
* mappings as this map. This operation may return misleading
* results if either map is concurrently modified during execution
* of this method.
*
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m o object to be compared for equality with this map
* @return {@code true} if the specified object is equal to this map
*/
public boolean equals(Object o) {
//内存地址是否相同
if (o != this) {
//是否为map类型
if (!(o instanceof Map))
return false;
//类型转化
Map<?,?> m = (Map<?,?>) o;
Node<K,V>[] t;
//记录table长度
int f = (t = table) == null ? 0 : t.length;
Traverser<K,f);
//遍历table,检查和o的value一致性
for (Node<K,V> p; (p = it.advance()) != null; ) {
V val = p.val;
Object v = m.get(p.key);
if (v == null || (v != val && !v.equals(val)))
return false;
}
//遍历o,检查自身key和value的合法性
for (Map.Entry<?,?> e : m.entrySet()) {
Object mk,mv,v;
if ((mk = e.getKey()) == null ||
(mv = e.getValue()) == null ||
(v = get(mk)) == null ||
(mv != v && !mv.equals(v)))
return false;
}
}
return true;
}
//旧版本中使用的类,存在的意义:序列化兼容性
static class Segment<K,V> extends <a href="https://www.jb51.cc/tag/reentrantlock/" target="_blank">reentrantlock</a> implements Serializable {
private static final long serialVersionUID = 2249069246763182397L;
final float loadFactor;
Segment(float lf) { this.loadFactor = lf; }
}
//用于序列化:将concurrenthashmap写入stream中.
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
// 用于序列化版本兼容
// Emulate segment cal<a href="https://www.jb51.cc/tag/cula/" target="_blank">cula</a>tion from prev<a href="https://www.jb51.cc/tag/IoU/" target="_blank">IoU</a>s version of this class
int sshift = 0;
int ssize = 1;
while (ssize < DEFAULT_CONCURRENCY_LEVEL) {
++sshift;
ssize <<= 1;
}
int segmentShift = 32 - sshift;
int segmentMask = ssize - 1;
@SuppressWarnings("unchecked")
Segment<K,V>[] segments = (Segment<K,V>[])
new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL];
for (int i = 0; i < segments.length; ++i)
segments[i] = new Segment<K,V>(LOAD_FACTOR);
s.putFields().put("segments",segments);
s.putFields().put("segmentShift",segmentShift);
s.putFields().put("segmentMask",segmentMask);
s.writeFields();
Node<K,V> p; (p = it.advance()) != null; ) {
s.writeObject(p.key);
s.writeObject(p.val);
}
}
s.writeObject(null);
s.writeObject(null);
segments = null; // throw away
}
private void rea<a href="https://www.jb51.cc/tag/dob/" target="_blank">dob</a>ject(java.io.ObjectInputStream s)
throws java.io.IOException,ClassNotFoundException {
/*
* 为了在典型情况下提高<a href="https://www.jb51.cc/tag/xingneng/" target="_blank">性能</a>，我们在读取时创建节点，然后在知道大小后放置在表中.
* 但是，我们还必须验证唯一性并处理过多的bin，这需要putVal机制的专用版本
*/
sizeCtl = -1; // force exclusion for table construction
s.defaultRea<a href="https://www.jb51.cc/tag/dob/" target="_blank">dob</a>ject();
long size = 0L;
Node<K,V> p = null;
for (;;) {
@SuppressWarnings("unchecked")
K k = (K) s.rea<a href="https://www.jb51.cc/tag/dob/" target="_blank">dob</a>ject();
@SuppressWarnings("unchecked")
V v = (V) s.rea<a href="https://www.jb51.cc/tag/dob/" target="_blank">dob</a>ject();
if (k != null && v != null) {
p = new Node<K,V>(spread(k.hashCode()),k,p);
++size;
}
else
break;
}
if (size == 0L)
sizeCtl = 0;
else {
int n;
if (size >= (long)(MAXIMUM_CAPACITY >>> 1))
n = MAXIMUM_CAPACITY;
else {
int sz = (int)size;
n = tableSi<a href="https://www.jb51.cc/tag/zef/" target="_blank">zef</a>or(sz + (sz >>> 1) + 1);
}
@SuppressWarnings("unchecked")
Node<K,V>[] tab = (Node<K,V>[])new Node<?,?>[n];
int mask = n - 1;
long added = 0L;
while (p != null) {
boolean insertAtFront;
Node<K,V> next = p.next,f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
int h = p.hash,j = h & mask;
if ((f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t = tabAt(tab,j)) == null)
insertAtFront = true;
else {
K k = p.key;
if (f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t.hash < 0) {
TreeBin<K,V>)f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
if (t.putTreeVal(h,p.val) == null)
++added;
insertAtFront = false;
}
else {
int binCount = 0;
insertAtFront = true;
Node<K,V> q; K qk;
for (q = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t; q != null; q = q.next) {
if (q.hash == h &&
((qk = q.key) == k ||
(qk != null && k.equals(qk)))) {
insertAtFront = false;
break;
}
++binCount;
}
if (insertAtFront && binCount >= TREEIFY_THRESHOLD) {
insertAtFront = false;
++added;
p.next = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
TreeNode<K,V> hd = null,tl = null;
for (q = p; q != null; q = q.next) {
TreeNode<K,V> t = new TreeNode<K,V>
(q.hash,q.key,q.val,null);
if ((t.prev = tl) == null)
hd = t;
else
tl.next = t;
tl = t;
}
setTabAt(tab,j,new TreeBin<K,V>(hd));
}
}
}
if (insertAtFront) {
++added;
p.next = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
setTabAt(tab,p);
}
p = next;
}
table = tab;
sizeCtl = n - (n >>> 2);
baseCount = added;
}
}
/*-------ConcurrentMap<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>---------*/
//存在,替换,返回旧value;否则不操作,返回null
public V putIfAbsent(K key,true);
}
public boolean remove(Object key,Object value) {
if (key == null)
throw new NullPointerException();
return value != null && replaceNode(key,value) != null;
}
public boolean replace(K key,V oldValue,V newValue) {
if (key == null || oldValue == null || newValue == null)
throw new NullPointerException();
return replaceNode(key,newValue,oldValue) != null;
}
public V replace(K key,V value) {
if (key == null || value == null)
throw new NullPointerException();
return replaceNode(key,null);
}
/*--------Overrides在JDK8中Map接口扩展的<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>--------*/
//key有value,则返回value;
//否则返回参数值
public V g<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>rDefault(Object key,V defaultValue) {
V v;
return (v = get(key)) == null ? defaultValue : v;
}
public void forEach(BiConsumer<? super K,? super V> action) {
if (action == null) throw new NullPointerException();
Node<K,V> p; (p = it.advance()) != null; ) {
action.accept(p.key,p.val);
}
}
}
public void replaceAll(BiFunction<? super K,? super V,? extends V> function) {
if (function == null) throw new NullPointerException();
Node<K,V> p; (p = it.advance()) != null; ) {
V oldValue = p.val;
for (K key = p.key;;) {
V newValue = function.apply(key,oldValue);
if (newValue == null)
throw new NullPointerException();
if (replaceNode(key,oldValue) != null ||
(oldValue = get(key)) == null)
break;
}
}
}
}
/**
* 如果指定的键尚未与值关联，则尝试使用给定的映射<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>计算其值，并将其输入到该映射中，除非是null.
* 整个<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a><a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>是以原子方式执行的，因此每个键最多应用一次该<a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>。
* 在进行计算时，其他线程在此映射上的某些尝试更新操作可能会被阻止，因此计算应该简短并且不要尝试更新此map中的任何其他映射。
*/
public V co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent(K key,Function<? super K,? extends V> mappingFunction) {
if (key == null || mappingFunction == null)
throw new NullPointerException();
int h = spread(key.hashCode());
V val = null;
int binCount = 0;
for (Node<K,fh;
if (tab == null || (n = tab.length) == 0)
tab = initTable();
//不存在
else if ((f = tabAt(tab,i = (n - 1) & h)) == null) {
Node<K,V> r = new ReservationNode<K,V>();
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块,计算新值并插入map
synchronized (r) {
if (casTabAt(tab,r)) {
binCount = 1;
Node<K,V> node = null;
try {
if ((val = mappingFunction.apply(key)) != null)
node = new Node<K,V>(h,val,null);
} finally {
setTabAt(tab,node);
}
}
}
if (binCount != 0)
break;
}
//此节点为转移节点forwarding node
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
//存在,且不是转移节点
else {
boolean added = false;
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块:分链表和红黑树两种情况进行插入
synchronized (f) {
if (tabAt(tab,i) == f) {
if (fh >= 0) {
binCount = 1;
for (Node<K,V> e = f;; ++binCount) {
K ek; V ev;
if (e.hash == h &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
val = e.val;
break;
}
Node<K,V> pred = e;
if ((e = e.next) == null) {
if ((val = mappingFunction.apply(key)) != null) {
added = true;
pred.next = new Node<K,null);
}
break;
}
}
}
else if (f instanceof TreeBin) {
binCount = 2;
TreeBin<K,p;
if ((r = t.root) != null &&
(p = r.findTreeNode(h,null)) != null)
val = p.val;
else if ((val = mappingFunction.apply(key)) != null) {
added = true;
t.putTreeVal(h,val);
}
}
}
}
//插入后,判定是否需要将链表转为红黑树
if (binCount != 0) {
if (binCount >= TREEIFY_THRESHOLD)
treeifyBin(tab,i);
if (!added)
return val;
break;
}
}
}
//<a href="https://www.jb51.cc/tag/zengjia/" target="_blank">增加</a>节点个数
if (val != null)
addCount(1L,binCount);
return val;
}
/**
* 如果指定的键尚已经与值关联，则尝试使用给定的映射<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>计算其值，并更改该映射.
* 整个<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a><a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>是以原子方式执行的，因此每个键最多应用一次该<a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>。
* 在进行计算时，其他线程在此映射上的某些尝试更新操作可能会被阻止，因此计算应该简短并且不要尝试更新此map中的任何其他映射。
*/
public V co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfPresent(K key,BiFunction<? super K,? extends V> remappingFunction) {
if (key == null || remappingFunction == null)
throw new NullPointerException();
int h = spread(key.hashCode());
V val = null;
int delta = 0;
int binCount = 0;
for (Node<K,fh;
if (tab == null || (n = tab.length) == 0)
tab = initTable();
//如果为null,返回
else if ((f = tabAt(tab,i = (n - 1) & h)) == null)
break;
//如果为转移节点,帮助转移
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
//计算值并替换
else {
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块,分链表和红黑树节点讨论插入.
synchronized (f) {
if (tabAt(tab,pred = null;; ++binCount) {
K ek;
if (e.hash == h &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
val = remappingFunction.apply(key,e.val);
if (val != null)
e.val = val;
else {
delta = -1;
Node<K,V> en = e.next;
if (pred != null)
pred.next = en;
else
setTabAt(tab,en);
}
break;
}
pred = e;
if ((e = e.next) == null)
break;
}
}
else if (f instanceof TreeBin) {
binCount = 2;
TreeBin<K,null)) != null) {
val = remappingFunction.apply(key,p.val);
if (val != null)
p.val = val;
else {
delta = -1;
if (t.removeTreeNode(p))
setTabAt(tab,untreeify(t.first));
}
}
}
}
}
if (binCount != 0)
break;
}
}
if (delta != 0)
addCount((long)delta,binCount);
return val;
}
//指定key如果没有value,则为其计算一个value
public V compute(K key,fh;
//如果表为null,则初始化表
if (tab == null || (n = tab.length) == 0)
tab = initTable();
//如果指定位置为null
else if ((f = tabAt(tab,V>();
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块:为其计算值,并插入map
synchronized (r) {
if (casTabAt(tab,V> node = null;
try {
if ((val = remappingFunction.apply(key,null)) != null) {
delta = 1;
node = new Node<K,null);
}
} finally {
//插入map
setTabAt(tab,node);
}
}
}
if (binCount != 0)
break;
}
//如果指定位置为转移节点,当前线程转去帮忙转移节点
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
//同步代码块
else {
synchronized (f) {
if (tabAt(tab,i) == f) {
//链表节点
if (fh >= 0) {
binCount = 1;
for (Node<K,e.val);
//计算的value不为null,更改原value
if (val != null)
e.val = val;
//计算的value为null
else {
delta = -1;
Node<K,V> en = e.next;
//上<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点为为null,<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>当前节点
if (pred != null)
pred.next = en;
//上<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点为null
else
setTabAt(tab,en);
}
break;
}
pred = e;
if ((e = e.next) == null) {
val = remappingFunction.apply(key,null);
if (val != null) {
delta = 1;
pred.next =
new Node<K,null);
}
break;
}
}
}
//红黑树树节点
else if (f instanceof TreeBin) {
binCount = 1;
TreeBin<K,p;
if ((r = t.root) != null)
p = r.findTreeNode(h,null);
else
p = null;
V pv = (p == null) ? null : p.val;
val = remappingFunction.apply(key,pv);
if (val != null) {
if (p != null)
p.val = val;
else {
delta = 1;
t.putTreeVal(h,val);
}
}
else if (p != null) {
delta = -1;
if (t.removeTreeNode(p))
setTabAt(tab,untreeify(t.first));
}
}
}
}
if (binCount != 0) {
if (binCount >= TREEIFY_THRESHOLD)
treeifyBin(tab,i);
break;
}
}
}
if (delta != 0)
addCount((long)delta,binCount);
return val;
}
/**
* 如果指定的键尚未与（非空）值相关联，则将其与给定值value相关联。
* 否则，将该值替换为给定的重映射<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>的结果，或者如果为null则被移除.
* 整个<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a><a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>是以原子方式执行的。其他线程在此映射上的某些尝试更新操作可能会被阻止当计算<a href="https://www.jb51.cc/tag/zhengzaijinxing/" target="_blank">正在进行</a>时，所以计算应该简短，
* 并且不能尝试更新此Map的任何其他映射。
*/
public V merge(K key,BiFunction<? super V,? extends V> remappingFunction) {
if (key == null || value == null || remappingFunction == null)
throw new NullPointerException();
int h = spread(key.hashCode());
V val = null;
int delta = 0;
int binCount = 0;
for (Node<K,fh;
//如果tab为null,初始化table
if (tab == null || (n = tab.length) == 0)
tab = initTable();
//如果该散列位置没有元素,为null
else if ((f = tabAt(tab,i = (n - 1) & h)) == null) {
//利用CAS为索引i处节点赋值
if (casTabAt(tab,null))) {
delta = 1;
val = value;
break;
}
}
//如果table在进行resize,则当前线程帮忙去resize
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
//如果散列位置有数值
else {
//同步代码块:
synchronized (f) {
//查找i处的节点
if (tabAt(tab,i) == f) {
//如果为链表节点
if (fh >= 0) {
binCount = 1;
for (Node<K,pred = null;; ++binCount) {
K ek;
if (e.hash == h &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
val = remappingFunction.apply(e.val,value);
if (val != null)
e.val = val;
else {
delta = -1;
Node<K,V> en = e.next;
if (pred != null)
pred.next = en;
//原value=新value=null,则<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>当前节点
else
setTabAt(tab,en);
}
break;
}
pred = e;
if ((e = e.next) == null) {
delta = 1;
val = value;
pred.next =
new Node<K,null);
break;
}
}
}
//如果节点为红黑树节点
else if (f instanceof TreeBin) {
binCount = 2;
TreeBin<K,V> r = t.root;
TreeNode<K,V> p = (r == null) ? null :
r.findTreeNode(h,null);
val = (p == null) ? value :
remappingFunction.apply(p.val,value);
if (val != null) {
if (p != null)
p.val = val;
else {
delta = 1;
t.putTreeVal(h,binCount);
return val;
}
/*-----------Hashtable的传统<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>------------*/
//此<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>在<a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>上与containsValue（Object）完全相同
public boolean contains(Object value) {
return containsValue(value);
}
//返回key的枚举
public Enumeration<K> keys() {
Node<K,V>[] t;
int f = (t = table) == null ? 0 : t.length;
return new KeyI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,this);
}
//返回value的枚举
public Enumeration<V> elements() {
Node<K,V>[] t;
int f = (t = table) == null ? 0 : t.length;
return new ValueI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,this);
}
/*-----------ConcurrentHashMap-only methods------独有<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>------------*/
/**
* 返回映射的<a href="https://www.jb51.cc/tag/shuliang/" target="_blank">数量</a>。
* 求映射个数时,应该使用此<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>而不是size()<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>，因为ConcurrentHashMap包含映射个数可以比Integer.MAX_VALUE更多。
* 注意:本<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>返回的值是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>估计值;如果并发插入或<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>，实际计数可能会有所不同。
* @return the number of mappings
* @since 1.8
*/
public long mappingCount() {
long n = sumCount();
return (n < 0L) ? 0L : n; // ig<a href="https://www.jb51.cc/tag/nor/" target="_blank">nor</a>e transient negative values
}
/**
* 根据给定类型Boolean.TRUE,新建<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>Set,当然这个set也是由ConcurrentHashMap作为后备支撑的
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m <K> the element type of the returned set
* @return the new set
* @since 1.8
*/
public static <K> KeySetView<K,Boolean> newKeySet() {
return new KeySetView<K,Boolean>
(new ConcurrentHashMap<K,Boolean>(),Boolean.TRUE);
}
/**
* @since 1.8
*/
public static <K> KeySetView<K,Boolean> newKeySet(int initialCapacity) {
return new KeySetView<K,Boolean>(initialCapacity),Boolean.TRUE);
}
//根据给定的通用value,在add,addAll<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>中可以随意<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>值.这当然只适用于从该视图中为所有<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>使用相同值的情况。
public KeySetView<K,V> keySet(V mappedValue) {
if (mappedValue == null)
throw new NullPointerException();
return new KeySetView<K,mappedValue);
}
/* ---------------- Special Nodes 特殊节点 -------------- */
/**
* <a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>用于连接两个table的节点类。它包含<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>nextTable指针，用于指向下一张表。而且这个节点的key,next指针全部为null，
* 它的hash值为-1. 这里面定义的find的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>是从nextTable里进行<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a>节点，而不是以自身为头节点进行查找
*/
static final class ForwardingNode<K,V> extends Node<K,V> {
final Node<K,V>[] nextTable;
ForwardingNode(Node<K,V>[] tab) {
//hash值=MOVED=-1
super(MOVED,null);
this.nextTable = tab;
}
Node<K,Object k) {
// loop to avoid arbitrarily deep recursion on forwarding nodes
//循环以避免转发节点上的任意深度递归
outer: for (Node<K,V>[] tab = nextTable;;) {
Node<K,V> e; int n;
//如果table为null,or长度为0,or指定bin无元素
if (k == null || tab == null || (n = tab.length) == 0 ||
(e = tabAt(tab,(n - 1) & h)) == null)
return null;
//循环
for (;;) {
int eh; K ek;
if ((eh = e.hash) == h &&
((ek = e.key) == k || (ek != null && k.equals(ek))))
return e;
//哈希值<0
if (eh < 0) {
//如果是转发节点
if (e instanceof ForwardingNode) {
//更新查找到新table
tab = ((ForwardingNode<K,V>)e).nextTable;
continue outer;
}
//非转发节点,则直接查找
else
return e.find(h,k);
}
if ((e = e.next) == null)
return null;
}
}
}
}
//在co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent和co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>中的节点占位符
static final class ReservationNode<K,V> {
ReservationNode() {
super(RESERVED,null);
}
Node<K,Object k) {
return null;
}
}
/* ---------------- Table 初始化 and Resizing -------------- */
//返回用于调整大小为n的table的<a href="https://www.jb51.cc/tag/biaoji/" target="_blank">标记</a>位。左移RESIZE_STAMP_SHIFT二进制位时,数值必为负.
static final int resizeStamp(int n) {
return Integer.numberOfLeadingZeros(n) | (1 << (RESIZE_STAMP_BITS - 1));
}
//使用sizeCtl中记录的size值初始化table
//对于ConcurrentHashMap来说，<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>它的构造<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>仅仅是设置了一些参数而已。
//而整个table的初始化是在向ConcurrentHashMap中插入元素的时候发生的。
private final Node<K,V>[] initTable() {
Node<K,V>[] tab; int sc;
while ((tab = table) == null || tab.length == 0) {
//如果当前有线程在对table进行初始化,则当前线程被阻塞,这也可以看出ConcurrentHashMap的初始化只能由<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>线程完成.
if ((sc = sizeCtl) < 0)
Thread.yield(); // 初始化失败,进行自旋
//利用CAS方法把sizectl的值置为-1,防止其他线程进入,表示本线程正在进行初始化
else if (U.compareAndSwapInt(this,SIZECTL,sc,-1)) {
try {
if ((tab = table) == null || tab.length == 0) {
int n = (sc > 0) ? sc : DEFAULT_CAPACITY;
//初始化大小为n的node数组
@SuppressWarnings("unchecked")
Node<K,V>[] nt = (Node<K,?>[n];
table = tab = nt;
sc = n - (n >>> 2);////相当于0.75*n 设置<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>扩容的阈值
}
} finally {
sizeCtl = sc;//sizeCtl的值改为0.75*n
}
break;
}
}
return tab;
}
/**
* <a href="https://www.jb51.cc/tag/zengjia/" target="_blank">增加</a>节点个数，如果table太小而没有resize，则检查是否需要resize。如果已经调整大小，则可以帮助复制转移节点。转移后重新检查占用情况，
* 以确定是否还需要调整大小，因为resize总是比put操作滞后。
*/
private final void addCount(long x,int check) {
CounterCell[] as; long b,s;
if ((as = counterCells) != null ||
!U.compareAndSwapLong(this,BASECOUNT,b = baseCount,s = b + x)) {
CounterCell a; long v; int m;
boolean uncontended = true;
if (as == null || (m = as.length - 1) < 0 ||
(a = as[ThreadLocalRandom.getProbe() & m]) == null ||
!(uncontended =
U.compareAndSwapLong(a,CELLVALUE,v = a.value,v + x))) {
fullAddCount(x,uncontended);
return;
}
if (check <= 1)
return;
s = sumCount();
}
if (check >= 0) {
Node<K,nt; int n,sc;
while (s >= (long)(sc = sizeCtl) && (tab = table) != null &&
(n = tab.length) < MAXIMUM_CAPACITY) {
int rs = resizeStamp(n);
if (sc < 0) {
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
sc == rs + MAX_RESIZERS || (nt = nextTable) == null ||
transferIndex <= 0)
break;
if (U.compareAndSwapInt(this,sc + 1))
transfer(tab,nt);
}
else if (U.compareAndSwapInt(this,(rs << RESIZE_STAMP_SHIFT) + 2))
transfer(tab,null);
s = sumCount();
}
}
}
//如果resize<a href="https://www.jb51.cc/tag/zhengzaijinxing/" target="_blank">正在进行</a>,则多个线程帮助节点的复制操作.
final Node<K,V>[] helpTransfer(Node<K,V> f) {
Node<K,V>[] nextTab; int sc;
//如果tab不为null,且f为转移节点,且新table不为null
if (tab != null && (f instanceof ForwardingNode) &&
(nextTab = ((ForwardingNode<K,V>)f).nextTable) != null) {
//返回resize后的table的<a href="https://www.jb51.cc/tag/biaoji/" target="_blank">标记</a>位
int rs = resizeStamp(tab.length);
while (nextTab == nextTable && table == tab &&
(sc = sizeCtl) < 0) {
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
sc == rs + MAX_RESIZERS || transferIndex <= 0)
break;
if (U.compareAndSwapInt(this,sc + 1)) {
transfer(tab,nextTab);
break;
}
}
return nextTab;
}
return table;
}
//尝试将table大小设定为:1.5*size+1,以容纳元素
private final void tryPresize(int size) {
int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :
tableSi<a href="https://www.jb51.cc/tag/zef/" target="_blank">zef</a>or(size + (size >>> 1) + 1);
int sc;
while ((sc = sizeCtl) >= 0) {
Node<K,V>[] tab = table; int n;
if (tab == null || (n = tab.length) == 0) {
n = (sc > c) ? sc : c;
if (U.compareAndSwapInt(this,-1)) {
try {
if (table == tab) {
@SuppressWarnings("unchecked")
Node<K,?>[n];
table = nt;
sc = n - (n >>> 2);
}
} finally {
sizeCtl = sc;
}
}
}
else if (c <= sc || n >= MAXIMUM_CAPACITY)
break;
else if (tab == table) {
int rs = resizeStamp(n);
if (sc < 0) {
Node<K,V>[] nt;
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
sc == rs + MAX_RESIZERS || (nt = nextTable) == null ||
transferIndex <= 0)
break;
if (U.compareAndSwapInt(this,null);
}
}
}
/**
* 这是ConcurrentHashMa的扩容<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>
* 将每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin拷贝到新的table中
*/
private final void transfer(Node<K,V>[] nextTab) {
int n = tab.length,stride;
//如果可用<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a>数目>1,则stride=tab长度/<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a><a href="https://www.jb51.cc/tag/shuliang/" target="_blank">数量</a>
if ((stride = (N<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a> > 1) ? (n >>> 3) / N<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a> : n) < MIN_TRANSFER_STRIDE)
//如果此时stride<最小分割并行段数,则更新stride为最小分割并行段数
stride = MIN_TRANSFER_STRIDE; // subdivide range
//如果新table为null,则对新table初始化,长度为旧table的2倍
if (nextTab == null) { // initiating
try {
@SuppressWarnings("unchecked")
Node<K,?>[n << 1];//2倍扩容
nextTab = nt;
} catch (Throwable ex) { // try to <a href="https://www.jb51.cc/tag/cop/" target="_blank">cop</a>e with OOME
sizeCtl = Integer.MAX_VALUE;
return;
}
//nextTable指向新建table
nextTable = nextTab;
//转移索引改为n
transferIndex = n;
}
//新table长度
int nextn = nextTab.length;
//转移节点:设定为新table,hash值=-1,其他<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>为null
ForwardingNode<K,V> fwd = new ForwardingNode<K,V>(nextTab);
boolean advance = true;///并发扩容的关键<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a> 如果等于true 说明这个节点已经处理过
//确保在提交nextTab之前进行扫描
boolean finishing = false; // to ensure sweep before committing nextTab
for (int i = 0,bound = 0;;) {
Node<K,V> f; int fh;
////这个while循环体的作用就是在控制i-- 通过i--可以依次遍历原hash表中的节点
while (advance) {
int nextIndex,nextBound;
if (--i >= bound || finishing)
advance = false;
else if ((nextIndex = transferIndex) <= 0) {
i = -1;
advance = false;
}
else if (U.compareAndSwapInt
(this,TRANSFERINDEX,nextIndex,nextBound = (nextIndex > stride ?
nextIndex - stride : 0))) {
bound = nextBound;
i = nextIndex - 1;
advance = false;
}
}
if (i < 0 || i >= n || i + n >= nextn) {
int sc;
//如果所有的节点都已经完成复制工作 就把nextTable赋值给table 清空临时对象nextTabl
if (finishing) {
nextTable = null;
table = nextTab;
sizeCtl = (n << 1) - (n >>> 1);
return;
}
if (U.compareAndSwapInt(this,sc = sizeCtl,sc - 1)) {
if ((sc - 2) != resizeStamp(n) << RESIZE_STAMP_SHIFT)
return;
finishing = advance = true;
i = n; // recheck before commit
}
}
//i位置节点为null,原table中的i位置放入forwardNode节点，这个也是触发并发扩容的关键点；
else if ((f = tabAt(tab,i)) == null)
advance = casTabAt(tab,fwd);
//当前节点已经被复制过,直接跳过.是控制并发扩容的关键
else if ((fh = f.hash) == MOVED)
advance = true; // already processed
//同步代码块,复制节点,保证线程安全的复制,不重复不冲突
else {
synchronized (f) {
if (tabAt(tab,V> ln,hn;
//如果节点为链表节点
if (fh >= 0) {
int runBit = fh & n;
Node<K,V> lastRun = f;
//查找lastRun的位置
for (Node<K,V> p = f.next; p != null; p = p.next) {
int b = p.hash & n;
if (b != runBit) {
runBit = b;
lastRun = p;
}
}
if (runBit == 0) {
ln = lastRun;
hn = null;
}
else {
hn = lastRun;
ln = null;
}
//lastRun节点前的节点都会构造<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>反序链表,lastRun节点开始到后面的节点则顺序不变
for (Node<K,V> p = f; p != lastRun; p = p.next) {
int ph = p.hash; K pk = p.key; V pv = p.val;
if ((ph & n) == 0)
ln = new Node<K,V>(ph,pk,pv,ln);
else
hn = new Node<K,hn);
}
//在nextTable的i位置上插入<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>链表
setTabAt(nextTab,ln);
//在nextTable的i+n的位置上插入另<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>链表
setTabAt(nextTab,i + n,hn);
//在table的i位置上插入forwardNode节点 表示已经处理过该节点
setTabAt(tab,fwd);
//设置advance为true 返回到上面的while循环中 就可以执行i--操作
advance = true;
}
//如果被复制节点为红黑树节点包装类TreeBin,也做<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>反序处理，并且判断是否需要untreeify，
//把处理的结果分别放在nextTable的i和i+n的位置上
else if (f instanceof TreeBin) {
TreeBin<K,V> lo = null,loTail = null;
TreeNode<K,V> hi = null,hiTail = null;
int lc = 0,hc = 0;
for (Node<K,V> e = t.f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t; e != null; e = e.next) {
int h = e.hash;
TreeNode<K,V> p = new TreeNode<K,V>
(h,e.key,e.val,null);
if ((h & n) == 0) {
if ((p.prev = loTail) == null)
lo = p;
else
loTail.next = p;
loTail = p;
++lc;
}
else {
if ((p.prev = hiTail) == null)
hi = p;
else
hiTail.next = p;
hiTail = p;
++hc;
}
}
////如果扩容后已经不再需要tree的结构 反向转换为链表结构
ln = (lc <= UNTREEIFY_THRESHOLD) ? untreeify(lo) :
(hc != 0) ? new TreeBin<K,V>(lo) : t;
hn = (hc <= UNTREEIFY_THRESHOLD) ? untreeify(hi) :
(lc != 0) ? new TreeBin<K,V>(hi) : t;
//下面<a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>和链表处理一致
setTabAt(nextTab,ln);
setTabAt(nextTab,hn);
setTabAt(tab,fwd);
advance = true;
}
}
}
}
}
}
/* ---------------- Counter support 计数器<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a><a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>-------------- */
/**
* A padded cell for <a href="https://www.jb51.cc/tag/dis/" target="_blank">dis</a>tributing counts. Adapted from LongAdder
* and Striped64. See their internal docs for explanation.
* 用于分发计数的填充单元格。改编自LongAdder和Striped64。请参阅他们的内部文档以获得解释。
* 用于辅助sumCount()<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>
*/
@sun.misc.Contended static final class CounterCell {
//内存可见value
volatile long value;
CounterCell(long x) { value = x; }
}
//ConcurrentHashMap中节点总数
final long sumCount() {
CounterCell[] as = counterCells; CounterCell a;
long sum = baseCount;
if (as != null) {
for (int i = 0; i < as.length; ++i) {
if ((a = as[i]) != null)
sum += a.value;
}
}
return sum;
}
/**
* LongAdder是java8新增的.
* LongAdders与ConcurrentHashMap一起使用，以维护可伸缩的频率映射（一种直方图或多重集）。
* 例如，要为ConcurrentHashMap<String，LongAdder> freqs <a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a><a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>计数，
* 初始化（如果尚未存在），可以使用freqs.co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent（k - > new LongAdder（））
*/
private final void fullAddCount(long x,boolean wasUncontended) {
int h;
if ((h = ThreadLocalRandom.getProbe()) == 0) {
ThreadLocalRandom.localInit(); // force initialization
h = ThreadLocalRandom.getProbe();
wasUncontended = true;
}
boolean collide = false; // True if last slot nonempty
for (;;) {
CounterCell[] as; CounterCell a; int n; long v;
if ((as = counterCells) != null && (n = as.length) > 0) {
if ((a = as[(n - 1) & h]) == null) {
if (cellsBusy == 0) { // Try to attach new Cell
CounterCell r = new CounterCell(x); // Optimistic create
if (cellsBusy == 0 &&
U.compareAndSwapInt(this,CELLSBUSY,1)) {
boolean created = false;
try { // Recheck under lock
CounterCell[] rs; int m,j;
if ((rs = counterCells) != null &&
(m = rs.length) > 0 &&
rs[j = (m - 1) & h] == null) {
rs[j] = r;
created = true;
}
} finally {
cellsBusy = 0;
}
if (created)
break;
continue; // Slot is <a href="https://www.jb51.cc/tag/Now/" target="_blank">Now</a> non-empty
}
}
collide = false;
}
else if (!wasUncontended) // CAS already k<a href="https://www.jb51.cc/tag/Now/" target="_blank">Now</a>n to fail
wasUncontended = true; // Continue after rehash
else if (U.compareAndSwapLong(a,v + x))
break;
else if (counterCells != as || n >= N<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a>)
collide = false; // At max size or stale
else if (!collide)
collide = true;
else if (cellsBusy == 0 &&
U.compareAndSwapInt(this,1)) {
try {
if (counterCells == as) {// Expand table unless stale
CounterCell[] rs = new CounterCell[n << 1];
for (int i = 0; i < n; ++i)
rs[i] = as[i];
counterCells = rs;
}
} finally {
cellsBusy = 0;
}
collide = false;
continue; // Retry with expanded table
}
h = ThreadLocalRandom.advanceProbe(h);
}
else if (cellsBusy == 0 && counterCells == as &&
U.compareAndSwapInt(this,1)) {
boolean init = false;
try { // Initialize table
if (counterCells == as) {
CounterCell[] rs = new CounterCell[2];
rs[h & 1] = new CounterCell(x);
counterCells = rs;
init = true;
}
} finally {
cellsBusy = 0;
}
if (init)
break;
}
else if (U.compareAndSwapLong(this,v = baseCount,v + x))
break; // Fall back on using base
}
}
/* ---------------- TreeBins 转换相关-------------- */
//在指定索引处替换掉所有的链表节点为红黑树节点;当然如果此时table特别小,则不执行转换操作,而应执行resize操作.
private final void treeifyBin(Node<K,int index) {
Node<K,V> b; int n,sc;
if (tab != null) {
if ((n = tab.length) < MIN_TREEIFY_CAPACITY)
tryPresize(n << 1);
else if ((b = tabAt(tab,index)) != null && b.hash >= 0) {
synchronized (b) {
if (tabAt(tab,index) == b) {
TreeNode<K,tl = null;
for (Node<K,V> e = b; e != null; e = e.next) {
TreeNode<K,V> p =
new TreeNode<K,V>(e.hash,null);
if ((p.prev = tl) == null)
hd = p;
else
tl.next = p;
tl = p;
}
//TreeBin封装了TreeNode节点,将索引index处节点设置为新的TreeBin节点
setTabAt(tab,index,V>(hd));
}
}
}
}
}
//将给定list中红黑树节点全部替换为链表节点,并返回链表
static <K,V> untreeify(Node<K,V> b) {
Node<K,tl = null;
for (Node<K,V> q = b; q != null; q = q.next) {
Node<K,V> p = new Node<K,V>(q.hash,null);
if (tl == null)
hd = p;
else
tl.next = p;
tl = p;
}
return hd;
}
/* ---------------- TreeNodes -------------- */
/**
* Nodes for use in TreeBins
* 也是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>核心的数据结构.
* 当链表长度过长的时候，会转换为TreeNode。但是与HashMap不相同的是，它并不是直接转换为红黑树，
* 而是把这些结点包装成TreeNode放在TreeBin对象中，由TreeBin完成对红黑树的包装。
* 而且TreeNode在ConcurrentHashMap集成自Node类，而并非HashMap中的集成自LinkedHashMap.Entry<K,V>类，
* 也就是说TreeNode带有next指针，这样做的目的是方便基于TreeBin的访问。
*/
static final class TreeNode<K,V> {
//用于红黑树节点连接,因为本身是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>链表,所以需要<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>指针指向双亲节点
TreeNode<K,V> parent; // red-black tree links
TreeNode<K,V> left;
TreeNode<K,V> right;
//前驱节点指针,用于<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>节点
TreeNode<K,V> prev; // needed to unlink next upon deletion
boolean red;
TreeNode(int hash,V> next,TreeNode<K,V> parent) {
super(hash,next);
this.parent = parent;
}
Node<K,Object k) {
return findTreeNode(h,null);
}
/**
* 从给定根节点出发,查找指定key的树节点.
* 红黑树节点排序规则:按照节点的hash值排序
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m h 查找节点hash值
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m k 查找节点key
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m kc
*
*/
final TreeNode<K,V> findTreeNode(int h,Class<?> kc) {
//指定key不为null
if (k != null) {
TreeNode<K,V> p = this;
do {
int ph,dir; K pk; TreeNode<K,V> q;
TreeNode<K,V> pl = p.left,pr = p.right;
//查找节点hash值比当前节点p的hash值小,则转向p的左孩子进行遍历,可见 红黑树按照节点的hash值排序
if ((ph = p.hash) > h)
p = pl;
//转右孩子
else if (ph < h)
p = pr;
//查找节点和当前p节点hash值和key都一样,则查找成功,返回查找节点
else if ((pk = p.key) == k || (pk != null && k.equals(pk)))
return p;
else if (pl == null)
p = pr;
else if (pr == null)
p = pl;
else if ((kc != null ||
(kc = comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bleClassFor(k)) != null) &&
(dir = compareComp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bles(kc,pk)) != 0)
p = (dir < 0) ? pl : pr;
//递归查找
else if ((q = pr.findTreeNode(h,kc)) != null)
return q;
else
p = pl;
} while (p != null);
}
return null;
}
}
/* ---------------- TreeBins -------------- */
/**
* TreeNodes用作bin的头节点.在实际的ConcurrentHashMap“数组”中，存放的是TreeBin对象，而不是TreeNode对象，这是与HashMap的区别。
* TreeBins不保存key和value,而是指向TreeNodes链表及其根节点.
* TreeBin还维持<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>读写锁,从而保证在红黑树重构前,优先完成读操作,然后再执行写操作.
*/
static final class TreeBin<K,V> {
//<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>TreeBin既要有指向根节点的指针,也要有指向第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点指针
TreeNode<K,V> root;//根节点
volatile TreeNode<K,V> f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;//第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点
volatile Thread waiter;//等待线程
volatile int lockState;//锁状态
//lockState的一些值
static final int WRITER = 1; // 持有写锁的锁状态值
static final int WAITER = 2; // 等待写锁的锁状态值
static final int READER = 4; // 设置读锁时的锁状态增量值
/**
* 插入节点时,如果hash值相同而又没有其它可比较的元素时,此<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>可用于打破此种插入僵局.
* 我们不需要<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>全局有序,只需要<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>插入规则,保证在调整平衡时可以维持等价关系.
* 僵局关系的进一步打破也使得测试变得简单了一些.
* 和hashmap<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>一样
*/
static int tieBreakOrder(Object a,Object b) {
int d;
//如果a为null,或者b为null,或者a和b是同<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>类的实
if (a == null || b == null ||
(d = a.getClass().getName().
compar<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>(b.getClass().getName())) == 0)//反射<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>类名
//identityHashCode():无论给定对象的类是否覆盖hashCode(),都会返回给定对象的哈希码,与<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>hashCode()返回的哈希码相同。
//如果传入参数a为null,则返回值为0;
d = (Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank">stem</a>.identityHashCode(a) <= Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank">stem</a>.identityHashCode(b) ?
-1 : 1);
return d;
}
//利用头节点为b的初始set节点集合,创建<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin,里面放了一棵红黑树
TreeBin(TreeNode<K,V> b) {
//这就它的构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>,TREEBIN=-1,树根节点的hash值
super(TREEBIN,null);
this.f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t = b;
TreeNode<K,V> r = null;
for (TreeNode<K,V> x = b,next; x != null; x = next) {
next = (TreeNode<K,V>)x.next;
x.left = x.right = null;
if (r == null) {
x.parent = null;
x.red = false;
r = x;
}
else {
K k = x.key;
int h = x.hash;
Class<?> kc = null;
for (TreeNode<K,V> p = r;;) {
int dir,ph;
K pk = p.key;
if ((ph = p.hash) > h)
dir = -1;
else if (ph < h)
dir = 1;
else if ((kc == null &&
(kc = comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bleClassFor(k)) == null) ||
(dir = compareComp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bles(kc,pk)) == 0)
dir = tieBreakOrder(k,pk);
TreeNode<K,V> xp = p;
if ((p = (dir <= 0) ? p.left : p.right) == null) {
x.parent = xp;
if (dir <= 0)
xp.left = x;
else
xp.right = x;
r = balanceInsertion(r,x);
break;
}
}
}
}
this.root = r;
assert checkInvariants(root);
}
//红黑树重构开始前,<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>写锁
private final void lockRoot() {
if (!U.compareAndSwapInt(this,LOCKSTATE,WRITER))
contendedLock(); // offload to sep<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>te method
}
//红黑树重构完成后,释放写锁
private final void unlockRoot() {
lockState = 0;
}
//root被锁定时,阻塞其他请求.
private final void contendedLock() {
boolean waiting = false;
for (int s;;) {
if (((s = lockState) & ~WAITER) == 0) {
if (U.compareAndSwapInt(this,s,WRITER)) {
if (waiting)
waiter = null;
return;
}
}
else if ((s & WAITER) == 0) {
if (U.compareAndSwapInt(this,s | WAITER)) {
waiting = true;
waiter = Thread.currentThread();
}
}
else if (waiting)
LockSupport.park(this);
}
}
//根据给定hash值和key查找树节点.
//首先尝试从树根节点开始查找
//如果<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>不到bin的锁,则<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a>需要线性时间:o(n),也就是从头到位底链表进行了遍历
//所以TreeBin的查找节点过程:时间复杂度为o(logN)或为o(N)
final Node<K,Object k) {
if (k != null) {
for (Node<K,V> e = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t; e != null; ) {
int s; K ek;
if (((s = lockState) & (WAITER|WRITER)) != 0) {
if (e.hash == h &&
((ek = e.key) == k || (ek != null && k.equals(ek))))
return e;
e = e.next;
}
else if (U.compareAndSwapInt(this,s + READER)) {
TreeNode<K,p;
try {
p = ((r = root) == null ? null :
r.findTreeNode(h,null));
} finally {
Thread w;
if (U.getAndAddInt(this,-READER) ==
(READER|WAITER) && (w = waiter) != null)
LockSupport.unpark(w);
}
return p;
}
}
}
return null;
}
//<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a><a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>树节点
final TreeNode<K,V> putTreeVal(int h,K k,V v) {
Class<?> kc = null;
boolean searched = false;
for (TreeNode<K,V> p = root;;) {
int dir,ph; K pk;
if (p == null) {
f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t = root = new TreeNode<K,null);
break;
}
else if ((ph = p.hash) > h)
dir = -1;
else if (ph < h)
dir = 1;
else if ((pk = p.key) == k || (pk != null && k.equals(pk)))
return p;
else if ((kc == null &&
(kc = comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bleClassFor(k)) == null) ||
(dir = compareComp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bles(kc,pk)) == 0) {
if (!searched) {
TreeNode<K,V> q,ch;
searched = true;
if (((ch = p.left) != null &&
(q = ch.findTreeNode(h,kc)) != null) ||
((ch = p.right) != null &&
(q = ch.findTreeNode(h,kc)) != null))
return q;
}
dir = tieBreakOrder(k,pk);
}
TreeNode<K,V> xp = p;
if ((p = (dir <= 0) ? p.left : p.right) == null) {
TreeNode<K,V> x,f = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t = x = new TreeNode<K,xp);
if (f != null)
f.prev = x;
if (dir <= 0)
xp.left = x;
else
xp.right = x;
if (!xp.red)
x.red = true;
else {
lockRoot();
try {
root = balanceInsertion(root,x);
} finally {
unlockRoot();
}
}
break;
}
}
assert checkInvariants(root);
return null;
}
/**
* 移除<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>树节点.在此<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>被<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>前此节点必须存在.
* 这比典型的红黑<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a><a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>更混乱，因为我们不能交换内部节点和其后继叶子节点的<a href="https://www.jb51.cc/tag/neirong/" target="_blank">内容</a>。
* 所以,取而代之的是交换树<a href="https://www.jb51.cc/tag/lianjie/" target="_blank">链接</a>。
* @return 返回值为true,代表<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>节点后,bin内节点太少,需要将红黑树转为链表.
*/
final boolean removeTreeNode(TreeNode<K,V> p) {
TreeNode<K,V> next = (TreeNode<K,V>)p.next;
TreeNode<K,V> pred = p.prev; // unlink traversal pointers
TreeNode<K,rl;
if (pred == null)
f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t = next;
else
pred.next = next;
if (next != null)
next.prev = pred;
if (f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t == null) {
root = null;
return true;
}
if ((r = root) == null || r.right == null || // too small
(rl = r.left) == null || rl.left == null)
return true;
lockRoot();
try {
TreeNode<K,V> replacement;
TreeNode<K,V> pl = p.left;
TreeNode<K,V> pr = p.right;
if (pl != null && pr != null) {
TreeNode<K,V> s = pr,sl;
while ((sl = s.left) != null) // find successor
s = sl;
boolean c = s.red; s.red = p.red; p.red = c; // swap colors
TreeNode<K,V> sr = s.right;
TreeNode<K,V> pp = p.parent;
if (s == pr) { // p was s's direct parent
p.parent = s;
s.right = p;
}
else {
TreeNode<K,V> sp = s.parent;
if ((p.parent = sp) != null) {
if (s == sp.left)
sp.left = p;
else
sp.right = p;
}
if ((s.right = pr) != null)
pr.parent = s;
}
p.left = null;
if ((p.right = sr) != null)
sr.parent = p;
if ((s.left = pl) != null)
pl.parent = s;
if ((s.parent = pp) == null)
r = s;
else if (p == pp.left)
pp.left = s;
else
pp.right = s;
if (sr != null)
replacement = sr;
else
replacement = p;
}
else if (pl != null)
replacement = pl;
else if (pr != null)
replacement = pr;
else
replacement = p;
if (replacement != p) {
TreeNode<K,V> pp = replacement.parent = p.parent;
if (pp == null)
r = replacement;
else if (p == pp.left)
pp.left = replacement;
else
pp.right = replacement;
p.left = p.right = p.parent = null;
}
root = (p.red) ? r : balanceDeletion(r,replacement);
if (p == replacement) { // detach pointers
TreeNode<K,V> pp;
if ((pp = p.parent) != null) {
if (p == pp.left)
pp.left = null;
else if (p == pp.right)
pp.right = null;
p.parent = null;
}
}
} finally {
unlockRoot();
}
assert checkInvariants(root);
return false;
}
/* --------------------红黑树<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,全部改自CLR算法---------------------------------------- */
//左旋
static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root,pp,rl;
if (p != null && (r = p.right) != null) {
if ((rl = p.right = r.left) != null)
rl.parent = p;
if ((pp = r.parent = p.parent) == null)
(root = r).red = false;
else if (pp.left == p)
pp.left = r;
else
pp.right = r;
r.left = p;
p.parent = r;
}
return root;
}
//右旋
static <K,V> rotateRight(TreeNode<K,V> l,lr;
if (p != null && (l = p.left) != null) {
if ((lr = p.left = l.right) != null)
lr.parent = p;
if ((pp = l.parent = p.parent) == null)
(root = l).red = false;
else if (pp.right == p)
pp.right = l;
else
pp.left = l;
l.right = p;
p.parent = l;
}
return root;
}
//插入后,调整平衡和颜色
static <K,V> balanceInsertion(TreeNode<K,V> x) {
x.red = true;
for (TreeNode<K,V> xp,xpp,xppl,xppr;;) {
if ((xp = x.parent) == null) {
x.red = false;
return x;
}
else if (!xp.red || (xpp = xp.parent) == null)
return root;
if (xp == (xppl = xpp.left)) {
if ((xppr = xpp.right) != null && xppr.red) {
xppr.red = false;
xp.red = false;
xpp.red = true;
x = xpp;
}
else {
if (x == xp.right) {
root = rotateLeft(root,x = xp);
xpp = (xp = x.parent) == null ? null : xp.parent;
}
if (xp != null) {
xp.red = false;
if (xpp != null) {
xpp.red = true;
root = rotateRight(root,xpp);
}
}
}
}
else {
if (xppl != null && xppl.red) {
xppl.red = false;
xp.red = false;
xpp.red = true;
x = xpp;
}
else {
if (x == xp.left) {
root = rotateRight(root,x = xp);
xpp = (xp = x.parent) == null ? null : xp.parent;
}
if (xp != null) {
xp.red = false;
if (xpp != null) {
xpp.red = true;
root = rotateLeft(root,xpp);
}
}
}
}
}
}
//<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>后调整平衡和颜色
static <K,V> balanceDeletion(TreeNode<K,V> x) {
for (TreeNode<K,xpl,xpr;;) {
if (x == null || x == root)
return root;
else if ((xp = x.parent) == null) {
x.red = false;
return x;
}
else if (x.red) {
x.red = false;
return root;
}
else if ((xpl = xp.left) == x) {
if ((xpr = xp.right) != null && xpr.red) {
xpr.red = false;
xp.red = true;
root = rotateLeft(root,xp);
xpr = (xp = x.parent) == null ? null : xp.right;
}
if (xpr == null)
x = xp;
else {
TreeNode<K,V> sl = xpr.left,sr = xpr.right;
if ((sr == null || !sr.red) &&
(sl == null || !sl.red)) {
xpr.red = true;
x = xp;
}
else {
if (sr == null || !sr.red) {
if (sl != null)
sl.red = false;
xpr.red = true;
root = rotateRight(root,xpr);
xpr = (xp = x.parent) == null ?
null : xp.right;
}
if (xpr != null) {
xpr.red = (xp == null) ? false : xp.red;
if ((sr = xpr.right) != null)
sr.red = false;
}
if (xp != null) {
xp.red = false;
root = rotateLeft(root,xp);
}
x = root;
}
}
}
else { // symmetric
if (xpl != null && xpl.red) {
xpl.red = false;
xp.red = true;
root = rotateRight(root,xp);
xpl = (xp = x.parent) == null ? null : xp.left;
}
if (xpl == null)
x = xp;
else {
TreeNode<K,V> sl = xpl.left,sr = xpl.right;
if ((sl == null || !sl.red) &&
(sr == null || !sr.red)) {
xpl.red = true;
x = xp;
}
else {
if (sl == null || !sl.red) {
if (sr != null)
sr.red = false;
xpl.red = true;
root = rotateLeft(root,xpl);
xpl = (xp = x.parent) == null ?
null : xp.left;
}
if (xpl != null) {
xpl.red = (xp == null) ? false : xp.red;
if ((sl = xpl.left) != null)
sl.red = false;
}
if (xp != null) {
xp.red = false;
root = rotateRight(root,xp);
}
x = root;
}
}
}
}
}
//递归不变检查,用于检查整个红黑树连接上是否有<a href="https://www.jb51.cc/tag/cuowu/" target="_blank">错误</a>
static <K,V> boolean checkInvariants(TreeNode<K,V> t) {
//tp双亲,tl左孩子,tr右孩子,tb前驱,tn后继
TreeNode<K,V> tp = t.parent,tl = t.left,tr = t.right,tb = t.prev,tn = (TreeNode<K,V>)t.next;
//双亲不为null,前驱的后继不是当前节点t,故连接<a href="https://www.jb51.cc/tag/cuowu/" target="_blank">错误</a>,返回false
if (tb != null && tb.next != t)
return false;
//后继不为null,后继的前驱不为当前节点t,故<a href="https://www.jb51.cc/tag/lianjie/" target="_blank">链接</a><a href="https://www.jb51.cc/tag/cuowu/" target="_blank">错误</a>,返回false
if (tn != null && tn.prev != t)
return false;
if (tp != null && t != tp.left && t != tp.right)
return false;
if (tl != null && (tl.parent != t || tl.hash > t.hash))
return false;
if (tr != null && (tr.parent != t || tr.hash < t.hash))
return false;
if (t.red && tl != null && tl.red && tr != null && tr.red)
return false;
if (tl != null && !checkInvariants(tl))
return false;
if (tr != null && !checkInvariants(tr))
return false;
return true;
}
private static final sun.misc.Unsafe U;
private static final long LOCKSTATE;
static {
try {
U = sun.misc.Unsafe.getUnsafe();
Class<?> k = TreeBin.class;
LOCKSTATE = U.objectFieldOffset
(k.getDeclaredField("lockState"));//反射<a href="https://www.jb51.cc/tag/huoquziduan/" target="_blank">获取字段</a>值
} catch (Exception e) {
throw new Error(e);
}
}
}
/* ----------------Table 遍历 -------------- */
//在继续使用当前table前,必须记录转发表的区域的表，其长度和当前遍历索引。
static final class TableStack<K,V> {
int length;
int index;
Node<K,V>[] tab;
TableStack<K,V> next;
}
/**
* 对诸如containsValue之类的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>要进行封装遍历.alsoserves是其他迭代器和分割器的基类.
* 遍历过程中,可能出现resize,为了面对可能的持续调整,需要记录大量的状态,因此很难通过volatile进行优化,* 即便如此，遍历仍然保持合理的吞吐量。通常情况下，迭代逐个进行遍历列表。但是，如果表已经调整大小，那么所有未来的步骤
* 必须遍历当前索引处的bin以及（index + baseSize）.
* 为了处理<a href="https://www.jb51.cc/tag/yonghu/" target="_blank">用户</a>间跨线程共享迭代器之<a href="https://www.jb51.cc/tag/jiande/" target="_blank">间的</a>冲突,如果迭代器索引边界失效,则迭代停止.
*/
static class Traverser<K,V> {
Node<K,V>[] tab; // current table; updated if resized
Node<K,V> next; // the next entry to use
TableStack<K,V> stack,spare; // to save/restore on ForwardingNodes
int index; // index of bin to use next
int baseIndex; // current index of initial table
int baseLimit; // index bound for initial table
final int baseSize; // initial table size
Traverser(Node<K,int size,int index,int limit) {
this.tab = tab;
this.baseSize = size;
this.baseIndex = this.index = index;
this.baseLimit = limit;
this.next = null;
}
//继续遍历,返回下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>有效节点,如果没有则返回null
final Node<K,V> advance() {
Node<K,V> e;
if ((e = next) != null)
e = e.next;
for (;;) {
Node<K,V>[] t; int i,n; // must use locals in checks
if (e != null)
return next = e;
if (baseIndex >= baseLimit || (t = tab) == null ||
(n = t.length) <= (i = index) || i < 0)
return next = null;
if ((e = tabAt(t,i)) != null && e.hash < 0) {
if (e instanceof ForwardingNode) {
tab = ((ForwardingNode<K,V>)e).nextTable;
e = null;
pushState(t,n);
continue;
}
else if (e instanceof TreeBin)
e = ((TreeBin<K,V>)e).f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
else
e = null;
}
if (stack != null)
recoverState(n);
else if ((index = i + baseSize) >= n)
index = ++baseIndex; // visit upper slots if present
}
}
//遇到转发节点时,保存遍历状态
private void pushState(Node<K,V>[] t,int n) {
TableStack<K,V> s = spare; // reuse if possible
if (s != null)
spare = s.next;
else
s = new TableStack<K,V>();
s.tab = t;
s.length = n;
s.index = i;
s.next = stack;
stack = s;
}
//取出遍历状态栈的栈定元素.
private void recoverState(int n) {
TableStack<K,V> s; int len;
while ((s = stack) != null && (index += (len = s.length)) >= n) {
n = len;
index = s.index;
tab = s.tab;
s.tab = null;
TableStack<K,V> next = s.next;
s.next = spare; // save for reuse
stack = next;
spare = s;
}
if (s == null && (index += baseSize) >= n)
index = ++baseIndex;
}
}
//基于key,entry的迭代器.在Traverser基础上<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>了一些变量以<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.remove<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>
static class BaseI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V> extends Traverser<K,V> {
final ConcurrentHashMap<K,V> map;
Node<K,V> lastReturned;
BaseI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,int limit,ConcurrentHashMap<K,V> map) {
super(tab,size,limit);
this.map = map;
advance();
}
public final boolean hasNext() { return next != null; }
public final boolean hasMoreElements() { return next != null; }
public final void remove() {
Node<K,V> p;
if ((p = lastReturned) == null)
throw new Ille<a href="https://www.jb51.cc/tag/gal/" target="_blank">gal</a>StateException();
lastReturned = null;
map.replaceNode(p.key,null);
}
}
//key迭代器
static final class KeyI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V> extends BaseI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K>,Enumeration<K> {
KeyI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,limit,map);
}
public final K next() {
Node<K,V> p;
if ((p = next) == null)
throw new NoSuchElementException();
K k = p.key;
lastReturned = p;
advance();
return k;
}
public final K nextElement() { return next(); }
}
//value迭代器
static final class ValueI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V>,Enumeration<V> {
ValueI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,map);
}
public final V next() {
Node<K,V> p;
if ((p = next) == null)
throw new NoSuchElementException();
V v = p.val;
lastReturned = p;
advance();
return v;
}
public final V nextElement() { return next(); }
}
//Entry迭代器
static final class EntryI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<Map.Entry<K,V>> {
EntryI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,map);
}
public final Map.Entry<K,V> next() {
Node<K,V> p;
if ((p = next) == null)
throw new NoSuchElementException();
K k = p.key;
V v = p.val;
lastReturned = p;
advance();
return new MapEntry<K,V>(k,map);
}
}
//从EntryI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor导出<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>Entry
static final class MapEntry<K,V> {
final K key; // non-null
V val; // non-null
final ConcurrentHashMap<K,V> map;
MapEntry(K key,V> map) {
this.key = key;
this.val = val;
this.map = map;
}
public K getKey() { return key; }
public V getValue() { return val; }
public int hashCode() { return key.hashCode() ^ val.hashCode(); }
public String toString() { return key + "=" + val; }
public boolean equals(Object o) {
Object k,v; Map.Entry<?,?>)o).getKey()) != null &&
(v = e.getValue()) != null &&
(k == key || k.equals(key)) &&
(v == val || v.equals(val)));
}
/**
* 设置我们的entry的value并写入map。
* 注意:返回的值<a href="https://www.jb51.cc/tag/zaizheli/" target="_blank">在这里</a>有点随便。因为可能返回的值已经被其它线程做过更改了,而返回值并未<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>到最新的值.
*/
public V setValue(V value) {
if (value == null) throw new NullPointerException();
V v = val;
val = value;
map.put(key,value);
return v;
}
}
//key分割器
static final class KeySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K> {
long est; // size estimate
KeySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,long est) {
super(tab,limit);
this.est = est;
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K> trySplit() {
int i,h;
return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
new KeySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>(tab,baseSize,baseLimit = h,est >>>= 1);
}
public void forEachRemaining(Consumer<? super K> action) {
if (action == null) throw new NullPointerException();
for (Node<K,V> p; (p = advance()) != null;)
action.accept(p.key);
}
public boolean tryAdvance(Consumer<? super K> action) {
if (action == null) throw new NullPointerException();
Node<K,V> p;
if ((p = advance()) == null)
return false;
action.accept(p.key);
return true;
}
public long estimateSize() { return est; }
public int <a href="https://www.jb51.cc/tag/characteristics/" target="_blank">characteristics</a>() {
return Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.<a href="https://www.jb51.cc/tag/dis/" target="_blank">dis</a>TINCT | Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.CONCURRENT |
Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.NONNULL;
}
}
//value分割器
static final class ValueSpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V> {
long est; // size estimate
ValueSpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,limit);
this.est = est;
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V> trySplit() {
int i,h;
return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
new ValueSpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,est >>>= 1);
}
public void forEachRemaining(Consumer<? super V> action) {
if (action == null) throw new NullPointerException();
for (Node<K,V> p; (p = advance()) != null;)
action.accept(p.val);
}
public boolean tryAdvance(Consumer<? super V> action) {
if (action == null) throw new NullPointerException();
Node<K,V> p;
if ((p = advance()) == null)
return false;
action.accept(p.val);
return true;
}
public long estimateSize() { return est; }
public int <a href="https://www.jb51.cc/tag/characteristics/" target="_blank">characteristics</a>() {
return Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.CONCURRENT | Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.NONNULL;
}
}
//entry分割器
static final class EntrySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<Map.Entry<K,V>> {
final ConcurrentHashMap<K,V> map; // To export MapEntry
long est; // size estimate
EntrySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,long est,limit);
this.map = map;
this.est = est;
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<Map.Entry<K,V>> trySplit() {
int i,h;
return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
new EntrySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,est >>>= 1,map);
}
public void forEachRemaining(Consumer<? super Map.Entry<K,V>> action) {
if (action == null) throw new NullPointerException();
for (Node<K,V> p; (p = advance()) != null; )
action.accept(new MapEntry<K,V>(p.key,p.val,map));
}
public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
if (action == null) throw new NullPointerException();
Node<K,V> p;
if ((p = advance()) == null)
return false;
action.accept(new MapEntry<K,map));
return true;
}
public long estimateSize() { return est; }
public int <a href="https://www.jb51.cc/tag/characteristics/" target="_blank">characteristics</a>() {
return Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.<a href="https://www.jb51.cc/tag/dis/" target="_blank">dis</a>TINCT | Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.CONCURRENT |
Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.NONNULL;
}
}
/*---------并行批量操作 P<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llel bulk operations---------*/
/**
* 计算批量任务的初始批次值。
* 在执行最终的操作之前,返回值将是将任务一分为二的<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>指数值exp2.我的理解是,如果返回为3,则是将任务分为8部分,并行处理.
* 此值计算速度很快，适合用作二划分
*/
final int batchFor(long b) {
long n;
if (b == Long.MAX_VALUE || (n = sumCount()) <= 1L || n < b)
return 0;
int sp = ForkJoinPool.getCommonPoolP<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelism() << 2; // slack of 4
return (b <= 0L || (n /= b) >= sp) ? sp : (int)n;
}
//@since 1.8
public void forEach(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,BiConsumer<? super K,? super V> action) {
if (action == null) throw new NullPointerException();
new ForEachMappingTask<K,V>
(null,batchFor(p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold),table,action).invoke();
}
//@since 1.8
public <U> void forEach(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> transformer,Consumer<? super U> action) {
if (transformer == null || action == null)
throw new NullPointerException();
new ForEachTransformedMappingTask<K,V,U>
(null,transformer,action).invoke();
}
/**
* 对每个(key,value)应用给定的<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a><a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>并返回<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>非空结果，如果没有，则返回null。
* 成功后，进一步的元素处理将被抑制，<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a><a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>的任何其他并行<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>的结果都将被忽略。
* @since 1.8
*/
public <U> U search(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> searchFunction) {
if (searchFunction == null) throw new NullPointerException();
return new SearchMappingsTask<K,searchFunction,new <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U>()).invoke();
}
//since 1.8,合并结果值
public <U> U reduce(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,BiFunction<? super U,? super U,? extends U> reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceMappingsTask<K,reducer).invoke();
}
/**
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m basis reduction操作的<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认初始化值
* @since 1.8
*/
public double reduc<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>Double(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleBiFunction<? super K,? super V> transformer,double basis,DoubleBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,basis,reducer).invoke();
}
//@since 1.8
public long reduc<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>Long(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToLongBiFunction<? super K,long basis,LongBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceMappingsToLongTask<K,reducer).invoke();
}
// @since 1.8
public int reduc<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>Int(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToIntBiFunction<? super K,int basis,IntBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceMappingsToIntTask<K,reducer).invoke();
}
/**
* Performs the given action for each key.
* @since 1.8
*/
public void forEachKey(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Consumer<? super K> action) {
if (action == null) throw new NullPointerException();
new ForEachKeyTask<K,action).invoke();
}
/**
* @since 1.8
*/
public <U> void forEachKey(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Consumer<? super U> action) {
if (transformer == null || action == null)
throw new NullPointerException();
new ForEachTransformedKeyTask<K,action).invoke();
}
/**
* 根据给定<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a><a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>,返回<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>非null结果.如果没有则返回null
* 成功后，进一步的元素处理将被抑制，<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a><a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>的任何其他并行<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>的结果都将被忽略。
* @since 1.8
*/
public <U> U searchKeys(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> searchFunction) {
if (searchFunction == null) throw new NullPointerException();
return new SearchKeysTask<K,new <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U>()).invoke();
}
/**
* 所有key的<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>合并操作
* @since 1.8
*/
public K reduceKeys(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? super K,? extends K> reducer) {
if (reducer == null) throw new NullPointerException();
return new ReduceKeysTask<K,reducer).invoke();
}
/**
* 对key的reduce操作
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold 并行被处理的元素的个数阈值
* @since 1.8
*/
public <U> U reduceKeys(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceKeysTask<K,reducer).invoke();
}
/**
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m basis reduction操作的初始化值
* @since 1.8
*/
public double reduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>uble(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super K> transformer,DoubleBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public long reduceKeysToLong(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToLongFunction<? super K> transformer,LongBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceKeysToLongTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public int reduceKeysToInt(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToIntFunction<? super K> transformer,IntBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceKeysToIntTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public void forEachValue(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Consumer<? super V> action) {
if (action == null)
throw new NullPointerException();
new ForEachValueTask<K,action).invoke();
}
/**
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold 并行被处理的元素的个数阈值
* @since 1.8
*/
public <U> void forEachValue(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Function<? super V,Consumer<? super U> action) {
if (transformer == null || action == null)
throw new NullPointerException();
new ForEachTransformedValueTask<K,action).invoke();
}
/**
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold 并行被处理的元素的个数阈值
* @since 1.8
*/
public <U> U searchValues(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> searchFunction) {
if (searchFunction == null) throw new NullPointerException();
return new SearchValuesTask<K,new <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U>()).invoke();
}
/**
*
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold t并行被处理的元素的个数阈值
* @since 1.8
*/
public V reduceValues(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends V> reducer) {
if (reducer == null) throw new NullPointerException();
return new ReduceValuesTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public <U> U reduceValues(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceValuesTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public double reduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>uble(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super V> transformer,DoubleBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public long reduceValuesToLong(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToLongFunction<? super V> transformer,LongBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceValuesToLongTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public int reduceValuesToInt(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToIntFunction<? super V> transformer,IntBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceValuesToIntTask<K,reducer).invoke();
}
/**
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold 并行被处理的元素的个数阈值
* @since 1.8
*/
public void forEachEntry(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Consumer<? super Map.Entry<K,V>> action) {
if (action == null) throw new NullPointerException();
new ForEachEntryTask<K,V>(null,action).invoke();
}
/**
* @since 1.8
*/
public <U> void forEachEntry(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Function<Map.Entry<K,Consumer<? super U> action) {
if (transformer == null || action == null)
throw new NullPointerException();
new ForEachTransformedEntryTask<K,action).invoke();
}
/**
* @since 1.8
*/
public <U> U searchEntries(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> searchFunction) {
if (searchFunction == null) throw new NullPointerException();
return new SearchEntriesTask<K,new <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U>()).invoke();
}
/**
* @since 1.8
*/
public Map.Entry<K,V> reduceEntries(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,BiFunction<Map.Entry<K,Map.Entry<K,? extends Map.Entry<K,V>> reducer) {
if (reducer == null) throw new NullPointerException();
return new ReduceEntriesTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public <U> U reduceEntries(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceEntriesTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public double reduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>uble(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<Map.Entry<K,V>> transformer,DoubleBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public long reduceEntriesToLong(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToLongFunction<Map.Entry<K,LongBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceEntriesToLongTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public int reduceEntriesToInt(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToIntFunction<Map.Entry<K,IntBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceEntriesToIntTask<K,reducer).invoke();
}
/* ----------------视图操作 Views -------------- */
/**
* Base class for views.
*/
abstract static class CollectionView<K,E>
implements Collection<E>,java.io.Serializable {
private static final long serialVersionUID = 7249069246763182397L;
final ConcurrentHashMap<K,V> map;
CollectionView(ConcurrentHashMap<K,V> map) { this.map = map; }
/**
* Returns the map <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> this view.
*
* @return the map <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> this view
*/
public ConcurrentHashMap<K,V> getMap() { return map; }
/**
* Removes all of the elements from this view,by removing all
* the mappings from the map <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> this view.
*/
public final void clear() { map.clear(); }
public final int size() { return map.size(); }
public final boolean isEmpty() { return map.isEmpty(); }
// implementations below rely on concrete classes supplying these
// abstract methods
/**
* Returns an i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor over the elements in this collection.
*
* <p>The returned i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor is
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
*
* @return an i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor over the elements in this collection
*/
public abstract I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<E> i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor();
public abstract boolean contains(Object o);
public abstract boolean remove(Object o);
private static final String oomeMsg = "<a href="https://www.jb51.cc/tag/required/" target="_blank">required</a> array size too large";
public final Object[] toArray() {
long sz = map.mappingCount();
if (sz > MAX_ARRAY_SIZE)
throw new OutOfMemoryError(oomeMsg);
int n = (int)sz;
Object[] r = new Object[n];
int i = 0;
for (E e : this) {
if (i == n) {
if (n >= MAX_ARRAY_SIZE)
throw new OutOfMemoryError(oomeMsg);
if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
n = MAX_ARRAY_SIZE;
else
n += (n >>> 1) + 1;
r = Arrays.<a href="https://www.jb51.cc/tag/cop/" target="_blank">cop</a>yOf(r,n);
}
r[i++] = e;
}
return (i == n) ? r : Arrays.<a href="https://www.jb51.cc/tag/cop/" target="_blank">cop</a>yOf(r,i);
}
@SuppressWarnings("unchecked")
public final <T> T[] toArray(T[] a) {
long sz = map.mappingCount();
if (sz > MAX_ARRAY_SIZE)
throw new OutOfMemoryError(oomeMsg);
int m = (int)sz;
T[] r = (a.length >= m) ? a :
(T[])<a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.reflect.Array
.newInstance(a.getClass().getComponentType(),m);
int n = r.length;
int i = 0;
for (E e : this) {
if (i == n) {
if (n >= MAX_ARRAY_SIZE)
throw new OutOfMemoryError(oomeMsg);
if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
n = MAX_ARRAY_SIZE;
else
n += (n >>> 1) + 1;
r = Arrays.<a href="https://www.jb51.cc/tag/cop/" target="_blank">cop</a>yOf(r,n);
}
r[i++] = (T)e;
}
if (a == r && i < n) {
r[i] = null; // null-terminate
return r;
}
return (i == n) ? r : Arrays.<a href="https://www.jb51.cc/tag/cop/" target="_blank">cop</a>yOf(r,i);
}
public final String toString() {
StringBuilder sb = new StringBuilder();
sb.append('[');
I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<E> it = i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor();
if (it.hasNext()) {
for (;;) {
Object e = it.next();
sb.append(e == this ? "(this Collection)" : e);
if (!it.hasNext())
break;
sb.append(',').append(' ');
}
}
return sb.append(']').toString();
}
public final boolean containsAll(Collection<?> c) {
if (c != this) {
for (Object e : c) {
if (e == null || !contains(e))
return false;
}
}
return true;
}
public final boolean removeAll(Collection<?> c) {
if (c == null) throw new NullPointerException();
boolean modified = false;
for (I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<E> it = i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(); it.hasNext();) {
if (c.contains(it.next())) {
it.remove();
modified = true;
}
}
return modified;
}
public final boolean retainAll(Collection<?> c) {
if (c == null) throw new NullPointerException();
boolean modified = false;
for (I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<E> it = i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(); it.hasNext();) {
if (!c.contains(it.next())) {
it.remove();
modified = true;
}
}
return modified;
}
}
/**
* ConcurrentHashMap键的集合视图，通过映射到<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>公共值,<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>操作可以具有选择性。
* 这个类不能直接实例化。
* @since 1.8
*/
public static class KeySetView<K,V> extends CollectionView<K,K>
implements Set<K>,java.io.Serializable {
private static final long serialVersionUID = 7249069246763182397L;
private final V value;
KeySetView(ConcurrentHashMap<K,V> map,V value) { // non-public
super(map);
this.value = value;
}
/**
* Returns the default mapped value for additions,* or {@code null} if additions are not supported.
*
* @return the default mapped value for additions,or {@code null}
* if not supported
*/
public V getMappedValue() { return value; }
/**
* {@inheritDoc}
* @throws NullPointerException if the specified key is null
*/
public boolean contains(Object o) { return map.containsKey(o); }
/**
* Removes the key from this map view,by removing the key (and its
* corresponding value) from the <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> map. This method does
* <a href="https://www.jb51.cc/tag/nothing/" target="_blank">nothing</a> if the key is not in the map.
*
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m o the key to be removed from the <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> map
* @return {@code true} if the <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> map contained the specified key
* @throws NullPointerException if the specified key is null
*/
public boolean remove(Object o) { return map.remove(o) != null; }
/**
* @return an i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor over the keys of the <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> map
*/
public I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K> i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
Node<K,V>[] t;
ConcurrentHashMap<K,V> m = map;
int f = (t = m.table) == null ? 0 : t.length;
return new KeyI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,m);
}
//<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>指定key,此时value为定义的<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认映射值
public boolean add(K e) {
V v;
if ((v = value) == null)
throw new UnsupportedOperationException();
return map.putVal(e,true) == null;
}
public boolean addAll(Collection<? extends K> c) {
boolean added = false;
V v;
if ((v = value) == null)
throw new UnsupportedOperationException();
for (K e : c) {
if (map.putVal(e,true) == null)
added = true;
}
return added;
}
public int hashCode() {
int h = 0;
for (K e : this)
h += e.hashCode();
return h;
}
public boolean equals(Object o) {
Set<?> c;
return ((o instanceof Set) &&
((c = (Set<?>)o) == this ||
(containsAll(c) && c.containsAll(this))));
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K> spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
Node<K,V> m = map;
long n = m.sumCount();
int f = (t = m.table) == null ? 0 : t.length;
return new KeySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,n < 0L ? 0L : n);
}
public void forEach(Consumer<? super K> action) {
if (action == null) throw new NullPointerException();
Node<K,V>[] t;
if ((t = map.table) != null) {
Traverser<K,t.length);
for (Node<K,V> p; (p = it.advance()) != null; )
action.accept(p.key);
}
}
}
/**
* A view of a ConcurrentHashMap as a {@link Collection} of
* values,in which additions are <a href="https://www.jb51.cc/tag/dis/" target="_blank">dis</a>abled. This class cannot be
* directly instantiated. See {@link #values()}.
*/
static final class ValuesView<K,V>
implements Collection<V>,java.io.Serializable {
private static final long serialVersionUID = 2249069246763182397L;
ValuesView(ConcurrentHashMap<K,V> map) { super(map); }
public final boolean contains(Object o) {
return map.containsValue(o);
}
public final boolean remove(Object o) {
if (o != null) {
for (I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V> it = i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(); it.hasNext();) {
if (o.equals(it.next())) {
it.remove();
return true;
}
}
}
return false;
}
public final I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V> i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
ConcurrentHashMap<K,V> m = map;
Node<K,V>[] t;
int f = (t = m.table) == null ? 0 : t.length;
return new ValueI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,m);
}
public final boolean add(V e) {
throw new UnsupportedOperationException();
}
public final boolean addAll(Collection<? extends V> c) {
throw new UnsupportedOperationException();
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V> spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
Node<K,V> m = map;
long n = m.sumCount();
int f = (t = m.table) == null ? 0 : t.length;
return new ValueSpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,n < 0L ? 0L : n);
}
public void forEach(Consumer<? super V> action) {
if (action == null) throw new NullPointerException();
Node<K,V> p; (p = it.advance()) != null; )
action.accept(p.val);
}
}
}
/**
* A view of a ConcurrentHashMap as a {@link Set} of (key,value)
* entries. This class cannot be directly instantiated. See
* {@link #entrySet()}.
*/
static final class EntrySetView<K,V>>
implements Set<Map.Entry<K,V>>,java.io.Serializable {
private static final long serialVersionUID = 2249069246763182397L;
EntrySetView(ConcurrentHashMap<K,V> map) { super(map); }
public boolean contains(Object o) {
Object k,r; Map.Entry<?,?>)o).getKey()) != null &&
(r = map.get(k)) != null &&
(v = e.getValue()) != null &&
(v == r || v.equals(r)));
}
public boolean remove(Object o) {
Object k,?>)o).getKey()) != null &&
(v = e.getValue()) != null &&
map.remove(k,v));
}
/**
* @return an i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor over the entries of the <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> map
*/
public I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<Map.Entry<K,V>> i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
ConcurrentHashMap<K,V>[] t;
int f = (t = m.table) == null ? 0 : t.length;
return new EntryI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,m);
}
public boolean add(Entry<K,V> e) {
return map.putVal(e.getKey(),false) == null;
}
public boolean addAll(Collection<? extends Entry<K,V>> c) {
boolean added = false;
for (Entry<K,V> e : c) {
if (add(e))
added = true;
}
return added;
}
public final int hashCode() {
int h = 0;
Node<K,V> p; (p = it.advance()) != null; ) {
h += p.hashCode();
}
}
return h;
}
public final boolean equals(Object o) {
Set<?> c;
return ((o instanceof Set) &&
((c = (Set<?>)o) == this ||
(containsAll(c) && c.containsAll(this))));
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<Map.Entry<K,V>> spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
Node<K,V> m = map;
long n = m.sumCount();
int f = (t = m.table) == null ? 0 : t.length;
return new EntrySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,n < 0L ? 0L : n,m);
}
public void forEach(Consumer<? super Map.Entry<K,V> p; (p = it.advance()) != null; )
action.accept(new MapEntry<K,map));
}
}
}
// -------------------------------------------------------
//批量任务的基类。从类Traverser重复一些字段和<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>，因为我们需要子类CountedCompleter。
@SuppressWarnings("serial")
abstract static class BulkTask<K,R> extends CountedCompleter<R> {
Node<K,V>[] tab; // same as Traverser
Node<K,V> next;
TableStack<K,spare;
int index;
int baseIndex;
int baseLimit;
final int baseSize;
int batch; // split control
BulkTask(BulkTask<K,?> par,int b,int f,V>[] t) {
super(par);
this.batch = b;
this.index = this.baseIndex = i;
if ((this.tab = t) == null)
this.baseSize = this.baseLimit = 0;
else if (par == null)
this.baseSize = this.baseLimit = t.length;
else {
this.baseLimit = f;
this.baseSize = par.baseSize;
}
}
/**
* Same as Traverser version
*/
final Node<K,n;
if (e != null)
return next = e;
if (baseIndex >= baseLimit || (t = tab) == null ||
(n = t.length) <= (i = index) || i < 0)
return next = null;
if ((e = tabAt(t,V>)e).f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
else
e = null;
}
if (stack != null)
recoverState(n);
else if ((index = i + baseSize) >= n)
index = ++baseIndex;
}
}
private void pushState(Node<K,V> s = spare;
if (s != null)
spare = s.next;
else
s = new TableStack<K,V>();
s.tab = t;
s.length = n;
s.index = i;
s.next = stack;
stack = s;
}
private void recoverState(int n) {
TableStack<K,V> next = s.next;
s.next = spare; // save for reuse
stack = next;
spare = s;
}
if (s == null && (index += baseSize) >= n)
index = ++baseIndex;
}
}
/*
* 任务类。使用常规
* 由于编译器无法知道我们已经对任务参数进行了空值检查，因此我们强制使用最简单的提升旁路来帮助避免复杂检查。
*/
@SuppressWarnings("serial")
static final class ForEachKeyTask<K,V>
extends BulkTask<K,Void> {
final Consumer<? super K> action;
ForEachKeyTask
(BulkTask<K,?> p,Consumer<? super K> action) {
super(p,b,t);
this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Consumer<? super K> action;
if ((action = this.action) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachKeyTask<K,V>
(this,batch >>>= 1,tab,action).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
for (Node<K,V> p; (p = advance()) != null;)
action.accept(p.key);
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachValueTask<K,Void> {
final Consumer<? super V> action;
ForEachValueTask
(BulkTask<K,Consumer<? super V> action) {
super(p,t);
this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Consumer<? super V> action;
if ((action = this.action) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachValueTask<K,V> p; (p = advance()) != null;)
action.accept(p.val);
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachEntryTask<K,Void> {
final Consumer<? super Entry<K,V>> action;
ForEachEntryTask
(BulkTask<K,Consumer<? super Entry<K,V>> action) {
super(p,t);
this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Consumer<? super Entry<K,V>> action;
if ((action = this.action) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachEntryTask<K,V> p; (p = advance()) != null; )
action.accept(p);
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachMappingTask<K,Void> {
final BiConsumer<? super K,? super V> action;
ForEachMappingTask
(BulkTask<K,? super V> action) {
super(p,t);
this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiConsumer<? super K,? super V> action;
if ((action = this.action) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachMappingTask<K,V> p; (p = advance()) != null; )
action.accept(p.key,p.val);
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachTransformedKeyTask<K,U>
extends BulkTask<K,Void> {
final Function<? super K,? extends U> transformer;
final Consumer<? super U> action;
ForEachTransformedKeyTask
(BulkTask<K,Consumer<? super U> action) {
super(p,t);
this.transformer = transformer; this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super K,? extends U> transformer;
final Consumer<? super U> action;
if ((transformer = this.transformer) != null &&
(action = this.action) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachTransformedKeyTask<K,U>
(this,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p.key)) != null)
action.accept(u);
}
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachTransformedValueTask<K,Void> {
final Function<? super V,? extends U> transformer;
final Consumer<? super U> action;
ForEachTransformedValueTask
(BulkTask<K,t);
this.transformer = transformer; this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super V,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachTransformedValueTask<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p.val)) != null)
action.accept(u);
}
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachTransformedEntryTask<K,Void> {
final Function<Map.Entry<K,? extends U> transformer;
final Consumer<? super U> action;
ForEachTransformedEntryTask
(BulkTask<K,t);
this.transformer = transformer; this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<Map.Entry<K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachTransformedEntryTask<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p)) != null)
action.accept(u);
}
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachTransformedMappingTask<K,Void> {
final BiFunction<? super K,? extends U> transformer;
final Consumer<? super U> action;
ForEachTransformedMappingTask
(BulkTask<K,t);
this.transformer = transformer; this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<? super K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachTransformedMappingTask<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p.key,p.val)) != null)
action.accept(u);
}
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class SearchKeysTask<K,U> {
final Function<? super K,? extends U> searchFunction;
final <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result;
SearchKeysTask
(BulkTask<K,? extends U> searchFunction,<a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result) {
super(p,t);
this.searchFunction = searchFunction; this.result = result;
}
public final U getRawResult() { return result.get(); }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super K,? extends U> searchFunction;
final <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result;
if ((searchFunction = this.searchFunction) != null &&
(result = this.result) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
if (result.get() != null)
return;
addToPendingCount(1);
new SearchKeysTask<K,result).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
while (result.get() == null) {
U u;
Node<K,V> p;
if ((p = advance()) == null) {
propagateCompletion();
break;
}
if ((u = searchFunction.apply(p.key)) != null) {
if (result.compareAndSet(null,u))
quietlyCompleteRoot();
break;
}
}
}
}
}
@SuppressWarnings("serial")
static final class SearchValuesTask<K,U> {
final Function<? super V,? extends U> searchFunction;
final <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result;
SearchValuesTask
(BulkTask<K,t);
this.searchFunction = searchFunction; this.result = result;
}
public final U getRawResult() { return result.get(); }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super V,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
if (result.get() != null)
return;
addToPendingCount(1);
new SearchValuesTask<K,V> p;
if ((p = advance()) == null) {
propagateCompletion();
break;
}
if ((u = searchFunction.apply(p.val)) != null) {
if (result.compareAndSet(null,u))
quietlyCompleteRoot();
break;
}
}
}
}
}
@SuppressWarnings("serial")
static final class SearchEntriesTask<K,U> {
final Function<Entry<K,? extends U> searchFunction;
final <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result;
SearchEntriesTask
(BulkTask<K,Function<Entry<K,t);
this.searchFunction = searchFunction; this.result = result;
}
public final U getRawResult() { return result.get(); }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<Entry<K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
if (result.get() != null)
return;
addToPendingCount(1);
new SearchEntriesTask<K,V> p;
if ((p = advance()) == null) {
propagateCompletion();
break;
}
if ((u = searchFunction.apply(p)) != null) {
if (result.compareAndSet(null,u))
quietlyCompleteRoot();
return;
}
}
}
}
}
@SuppressWarnings("serial")
static final class SearchMappingsTask<K,U> {
final BiFunction<? super K,? extends U> searchFunction;
final <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result;
SearchMappingsTask
(BulkTask<K,t);
this.searchFunction = searchFunction; this.result = result;
}
public final U getRawResult() { return result.get(); }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<? super K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
if (result.get() != null)
return;
addToPendingCount(1);
new SearchMappingsTask<K,V> p;
if ((p = advance()) == null) {
propagateCompletion();
break;
}
if ((u = searchFunction.apply(p.key,p.val)) != null) {
if (result.compareAndSet(null,u))
quietlyCompleteRoot();
break;
}
}
}
}
}
@SuppressWarnings("serial")
static final class ReduceKeysTask<K,K> {
final BiFunction<? super K,? extends K> reducer;
K result;
ReduceKeysTask<K,V> rights,nextRight;
ReduceKeysTask
(BulkTask<K,ReduceKeysTask<K,V> nextRight,? extends K> reducer) {
super(p,t); this.nextRight = nextRight;
this.reducer = reducer;
}
public final K getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<? super K,? extends K> reducer;
if ((reducer = this.reducer) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new ReduceKeysTask<K,rights,reducer)).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
K r = null;
for (Node<K,V> p; (p = advance()) != null; ) {
K u = p.key;
r = (r == null) ? u : u == null ? r : reducer.apply(r,u);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
ReduceKeysTask<K,V>
t = (ReduceKeysTask<K,V>)c,s = t.rights;
while (s != null) {
K tr,sr;
if ((sr = s.result) != null)
t.result = (((tr = t.result) == null) ? sr :
reducer.apply(tr,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class ReduceValuesTask<K,V> {
final BiFunction<? super V,? extends V> reducer;
V result;
ReduceValuesTask<K,nextRight;
ReduceValuesTask
(BulkTask<K,ReduceValuesTask<K,? extends V> reducer) {
super(p,t); this.nextRight = nextRight;
this.reducer = reducer;
}
public final V getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<? super V,? extends V> reducer;
if ((reducer = this.reducer) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new ReduceValuesTask<K,reducer)).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
V r = null;
for (Node<K,V> p; (p = advance()) != null; ) {
V v = p.val;
r = (r == null) ? v : reducer.apply(r,v);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
ReduceValuesTask<K,V>
t = (ReduceValuesTask<K,s = t.rights;
while (s != null) {
V tr,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class ReduceEntriesTask<K,V>> {
final BiFunction<Map.Entry<K,V>> reducer;
Map.Entry<K,V> result;
ReduceEntriesTask<K,nextRight;
ReduceEntriesTask
(BulkTask<K,ReduceEntriesTask<K,BiFunction<Entry<K,V>> reducer) {
super(p,t); this.nextRight = nextRight;
this.reducer = reducer;
}
public final Map.Entry<K,V> getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<Map.Entry<K,V>> reducer;
if ((reducer = this.reducer) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new ReduceEntriesTask<K,reducer)).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
Map.Entry<K,V> r = null;
for (Node<K,V> p; (p = advance()) != null; )
r = (r == null) ? p : reducer.apply(r,p);
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
ReduceEntriesTask<K,V>
t = (ReduceEntriesTask<K,s = t.rights;
while (s != null) {
Map.Entry<K,V> tr,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
//MapReduce
@SuppressWarnings("serial")
static final class MapReduceKeysTask<K,? extends U> transformer;
final BiFunction<? super U,? extends U> reducer;
U result;
MapReduceKeysTask<K,U> rights,nextRight;
MapReduceKeysTask
(BulkTask<K,MapReduceKeysTask<K,U> nextRight,? extends U> reducer) {
super(p,t); this.nextRight = nextRight;
this.transformer = transformer;
this.reducer = reducer;
}
public final U getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super K,? extends U> transformer;
final BiFunction<? super U,? extends U> reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceKeysTask<K,reducer)).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
U r = null;
for (Node<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p.key)) != null)
r = (r == null) ? u : reducer.apply(r,u);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceKeysTask<K,U>
t = (MapReduceKeysTask<K,U>)c,s = t.rights;
while (s != null) {
U tr,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceValuesTask<K,? extends U> reducer;
U result;
MapReduceValuesTask<K,nextRight;
MapReduceValuesTask
(BulkTask<K,MapReduceValuesTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.reducer = reducer;
}
public final U getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super V,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceValuesTask<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p.val)) != null)
r = (r == null) ? u : reducer.apply(r,u);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceValuesTask<K,U>
t = (MapReduceValuesTask<K,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceEntriesTask<K,U> {
final Function<Map.Entry<K,? extends U> reducer;
U result;
MapReduceEntriesTask<K,nextRight;
MapReduceEntriesTask
(BulkTask<K,MapReduceEntriesTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.reducer = reducer;
}
public final U getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<Map.Entry<K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceEntriesTask<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p)) != null)
r = (r == null) ? u : reducer.apply(r,u);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceEntriesTask<K,U>
t = (MapReduceEntriesTask<K,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceMappingsTask<K,? extends U> reducer;
U result;
MapReduceMappingsTask<K,nextRight;
MapReduceMappingsTask
(BulkTask<K,MapReduceMappingsTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.reducer = reducer;
}
public final U getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<? super K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceMappingsTask<K,p.val)) != null)
r = (r == null) ? u : reducer.apply(r,u);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceMappingsTask<K,U>
t = (MapReduceMappingsTask<K,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,Double> {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super K> transformer;
final DoubleBinaryOperator reducer;
final double basis;
double result;
MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,nextRight;
MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask
(BulkTask<K,MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,DoubleBinaryOperator reducer) {
super(p,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Double getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super K> transformer;
final DoubleBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
double r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,r,reducer)).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
for (Node<K,V> p; (p = advance()) != null; )
r = reducer.applyAsDouble(r,transformer.applyAsDouble(p.key));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,V>
t = (MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,s = t.rights;
while (s != null) {
t.result = reducer.applyAsDouble(t.result,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,Double> {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super V> transformer;
final DoubleBinaryOperator reducer;
final double basis;
double result;
MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,nextRight;
MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask
(BulkTask<K,MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Double getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super V> transformer;
final DoubleBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
double r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,transformer.applyAsDouble(p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,V>
t = (MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,Double> {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<Map.Entry<K,V>> transformer;
final DoubleBinaryOperator reducer;
final double basis;
double result;
MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,nextRight;
MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask
(BulkTask<K,MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Double getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<Map.Entry<K,V>> transformer;
final DoubleBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
double r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,transformer.applyAsDouble(p));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,V>
t = (MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,Double> {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleBiFunction<? super K,? super V> transformer;
final DoubleBinaryOperator reducer;
final double basis;
double result;
MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,nextRight;
MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask
(BulkTask<K,MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Double getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleBiFunction<? super K,? super V> transformer;
final DoubleBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
double r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,transformer.applyAsDouble(p.key,p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,V>
t = (MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceKeysToLongTask<K,Long> {
final ToLongFunction<? super K> transformer;
final LongBinaryOperator reducer;
final long basis;
long result;
MapReduceKeysToLongTask<K,nextRight;
MapReduceKeysToLongTask
(BulkTask<K,MapReduceKeysToLongTask<K,LongBinaryOperator reducer) {
super(p,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Long getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToLongFunction<? super K> transformer;
final LongBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
long r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceKeysToLongTask<K,V> p; (p = advance()) != null; )
r = reducer.applyAsLong(r,transformer.applyAsLong(p.key));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceKeysToLongTask<K,V>
t = (MapReduceKeysToLongTask<K,s = t.rights;
while (s != null) {
t.result = reducer.applyAsLong(t.result,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceValuesToLongTask<K,Long> {
final ToLongFunction<? super V> transformer;
final LongBinaryOperator reducer;
final long basis;
long result;
MapReduceValuesToLongTask<K,nextRight;
MapReduceValuesToLongTask
(BulkTask<K,MapReduceValuesToLongTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Long getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToLongFunction<? super V> transformer;
final LongBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
long r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceValuesToLongTask<K,transformer.applyAsLong(p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceValuesToLongTask<K,V>
t = (MapReduceValuesToLongTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceEntriesToLongTask<K,Long> {
final ToLongFunction<Map.Entry<K,V>> transformer;
final LongBinaryOperator reducer;
final long basis;
long result;
MapReduceEntriesToLongTask<K,nextRight;
MapReduceEntriesToLongTask
(BulkTask<K,MapReduceEntriesToLongTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Long getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToLongFunction<Map.Entry<K,V>> transformer;
final LongBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
long r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceEntriesToLongTask<K,transformer.applyAsLong(p));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceEntriesToLongTask<K,V>
t = (MapReduceEntriesToLongTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceMappingsToLongTask<K,Long> {
final ToLongBiFunction<? super K,? super V> transformer;
final LongBinaryOperator reducer;
final long basis;
long result;
MapReduceMappingsToLongTask<K,nextRight;
MapReduceMappingsToLongTask
(BulkTask<K,MapReduceMappingsToLongTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Long getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToLongBiFunction<? super K,? super V> transformer;
final LongBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
long r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceMappingsToLongTask<K,transformer.applyAsLong(p.key,p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceMappingsToLongTask<K,V>
t = (MapReduceMappingsToLongTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceKeysToIntTask<K,Integer> {
final ToIntFunction<? super K> transformer;
final IntBinaryOperator reducer;
final int basis;
int result;
MapReduceKeysToIntTask<K,nextRight;
MapReduceKeysToIntTask
(BulkTask<K,MapReduceKeysToIntTask<K,IntBinaryOperator reducer) {
super(p,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Integer getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToIntFunction<? super K> transformer;
final IntBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
int r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceKeysToIntTask<K,V> p; (p = advance()) != null; )
r = reducer.applyAsInt(r,transformer.applyAsInt(p.key));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceKeysToIntTask<K,V>
t = (MapReduceKeysToIntTask<K,s = t.rights;
while (s != null) {
t.result = reducer.applyAsInt(t.result,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceValuesToIntTask<K,Integer> {
final ToIntFunction<? super V> transformer;
final IntBinaryOperator reducer;
final int basis;
int result;
MapReduceValuesToIntTask<K,nextRight;
MapReduceValuesToIntTask
(BulkTask<K,MapReduceValuesToIntTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Integer getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToIntFunction<? super V> transformer;
final IntBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
int r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceValuesToIntTask<K,transformer.applyAsInt(p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceValuesToIntTask<K,V>
t = (MapReduceValuesToIntTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceEntriesToIntTask<K,Integer> {
final ToIntFunction<Map.Entry<K,V>> transformer;
final IntBinaryOperator reducer;
final int basis;
int result;
MapReduceEntriesToIntTask<K,nextRight;
MapReduceEntriesToIntTask
(BulkTask<K,MapReduceEntriesToIntTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Integer getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToIntFunction<Map.Entry<K,V>> transformer;
final IntBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
int r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceEntriesToIntTask<K,transformer.applyAsInt(p));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceEntriesToIntTask<K,V>
t = (MapReduceEntriesToIntTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceMappingsToIntTask<K,Integer> {
final ToIntBiFunction<? super K,? super V> transformer;
final IntBinaryOperator reducer;
final int basis;
int result;
MapReduceMappingsToIntTask<K,nextRight;
MapReduceMappingsToIntTask
(BulkTask<K,MapReduceMappingsToIntTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Integer getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToIntBiFunction<? super K,? super V> transformer;
final IntBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
int r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceMappingsToIntTask<K,transformer.applyAsInt(p.key,p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceMappingsToIntTask<K,V>
t = (MapReduceMappingsToIntTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
/*-------Unsafe mechanics------*/
/**
* unsafe<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块控制了一些<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>的<a href="https://www.jb51.cc/tag/xiugai/" target="_blank">修改</a>工作，比如最常用的SIZECTL 。
* <a href="https://www.jb51.cc/tag/zaizhe/" target="_blank">在这</a>一版本的concurrentHashMap中，大量应用来的CAS<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>进行变量、<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>的<a href="https://www.jb51.cc/tag/xiugai/" target="_blank">修改</a>工作。利用CAS进行无锁操作，可以大大提高<a href="https://www.jb51.cc/tag/xingneng/" target="_blank">性能</a>。
* static<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块中:大量使用了反射
*/
private static final sun.misc.Unsafe U;
private static final long SIZECTL;
private static final long TRANSFERINDEX;
private static final long BASECOUNT;
private static final long CELLSBUSY;
private static final long CELLVALUE;
private static final long ABASE;
private static final int ASHIFT;
static {
try {
U = sun.misc.Unsafe.getUnsafe();
Class<?> k = ConcurrentHashMap.class;
SIZECTL = U.objectFieldOffset
(k.getDeclaredField("sizeCtl"));
TRANSFERINDEX = U.objectFieldOffset
(k.getDeclaredField("transferIndex"));
BASECOUNT = U.objectFieldOffset
(k.getDeclaredField("baseCount"));
CELLSBUSY = U.objectFieldOffset
(k.getDeclaredField("cellsBusy"));
Class<?> ck = CounterCell.class;
CELLVALUE = U.objectFieldOffset
(ck.getDeclaredField("value"));
Class<?> ak = Node[].class;
ABASE = U.arrayBa<a href="https://www.jb51.cc/tag/SEO/" title="SEO">SEO</a>ffset(ak);
int scale = U.arrayIndexScale(ak);
if ((scale & (scale - 1)) != 0)
throw new Error("data type scale not a power of two");
ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
} catch (Exception e) {
throw new Error(e);
}
}
}
package sourcecode.analysis;
/**
* @Author: cxh
* @CreateTime: 18/4/3 16:29
* @ProjectName: JavaBaseTest
*/
import java.io.ObjectStreamField;
import java.io.Serializable;
import <a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.*;
import <a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.reflect.P<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>meterizedType;
import <a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.reflect.Type;
import java.util.AbstractMap;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>tor;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CountedCompleter;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.atomic.<a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a>;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.<a href="https://www.jb51.cc/tag/reentrantlock/" target="_blank">reentrantlock</a>;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.BinaryOperator;
import java.util.function.Consumer;
import java.util.function.DoubleBinaryOperator;
import java.util.function.Function;
import java.util.function.IntBinaryOperator;
import java.util.function.LongBinaryOperator;
import java.util.function.T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleBiFunction;
import java.util.function.T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction;
import java.util.function.ToIntBiFunction;
import java.util.function.ToIntFunction;
import java.util.function.ToLongBiFunction;
import java.util.function.ToLongFunction;
import java.util.stream.Stream;
/**
* Hashtable<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>高并发检索,同时<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>高并发更新.
* ConcurrentHashMap和Hashtable遵守相同的<a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>规范,并且包含与Hashtable每种<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>相对应的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>版本.
* 但是，尽管所有操作都是线程安全的，但检索操作并不需要锁定,并且没有任何访问操作需要锁定全表.
* 这个类可以在依赖线程安全性的程序中与Hashtable完全互操作，但不依赖于它的同步细节.
*
* 检索操作(<a href="https://www.jb51.cc/tag/baokuo/" target="_blank">包括</a>get)通常不会对表加锁,因此可能会和更新操作(如put,remove)同时发生.
* 检索反映了最近完成的更新操作的结果.更正式的说:对<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>key的value的更新操作和读操作遵守happens-before
* 原则,所以同时发生检索和更新操作时,更新操作先执行,读操作<a href="https://www.jb51.cc/tag/houzhixing/" target="_blank">后执行</a>,从而保证了检索操作<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>的值一定是最新线程
* 更新的值.
* 对整体操作(如putAll和clear),并发检索可能只会反映出一部分条目的插入和<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>.同样的,I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tors,Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tors
* 和Enumerations只是在一定程度上反映了哈希表的状态or反映的是从i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor/enumeration它们创建后哈希表的状态.
* 它们并不会抛出并发异常ConcurrentModificationException.但是，迭代器被设计为一次只能由<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>线程使用.
* 请记住，聚合状态<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>的结果<a href="https://www.jb51.cc/tag/baokuo/" target="_blank">包括</a>:size,isEmpty,containsValue通常都是仅当map不在其它线程中进行并发更新时才有用.
* 否则，这些<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>的结果反映了可能足以用于监视或估计目的的暂态，但不适用于程序控制。
*
* 当碰撞冲突很多时(如不同hash值的key通过取模运算后进入了相同的slot),table会<a href="https://www.jb51.cc/tag/zidong/" target="_blank">自动</a>扩容,* slot扩容后大小为原来的2倍(和扩容时0.75<a href="https://www.jb51.cc/tag/fuzai/" target="_blank">负载</a>因子阈值保持一致)
* 随着映射的<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>和<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>，这个平均值可能会有很大的变化，但是总的来说，针对散列表,这已经是在时间/空间上做了折衷.
* 但是，调整这个或任何其他类型的哈希表可能是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>相对较慢的操作.在可能的情况下，通过构造器<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>,指定initialCapacity
* 是比较好的方式.另外<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>可选的构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>参数loadFactor提供了另一种定制初始表容量的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>，通过指定要用于计算给定元素数
* 分配空间量的表密度来<a href="https://www.jb51.cc/tag/zidingyi/" target="_blank">自定义</a>初始表容量.此外，为了与此类的以前版本兼容，构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>可以选择指定预期的concurrencyLevel
* 作为内部大小调整的附加<a href="https://www.jb51.cc/tag/tishi/" target="_blank">提示</a>.
* 注意:如果很多key都用一样的hashcode,则哈希表的<a href="https://www.jb51.cc/tag/xingneng/" target="_blank">性能</a>一定会降低.为了减弱这种影响,当key是可比较的对象时(实现了
* Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble接口),则ConcurrentHashMap可以通过对key的排序来打破这种关系.
*
* ConcurrentHashMap的Set<a href="https://www.jb51.cc/tag/duixiangchuangjian/" target="_blank">对象创建</a>方式有:newKeySet(),newKeySet(int),* 如果所有的key都是有效的,且values都无效(or所有的value值都一样),则还有一种视图创建方式:keySet(Object).
*
* ConcurrentHashMap可以用作可伸缩频率map（直方图或多重集的一种形式）,这可以使用LongAdder作为value,* 通过co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent来初始化.比如:
* 向ConcurrentHashMap<String,LongAdder>类型的变量freqs<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a><a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>count,你可以使用lambda表达式如下:
* freqs.co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent(k -> new LongAdder()).increment();
*
* 此类及其视图和迭代器实现了Map和I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor接口的所有可选<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>。
*
* ConcurrentHashMap的key和value都不能为null,这一点和hashtable一致.
*
* ConcurrentHashMap<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>一组顺序操作和并行的批量操作,和大多数Stream<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>不同,该操作被设计为线程安全
* 且经常应用于即使由其他线程同时更新的映射;例如，在计算共享<a href="https://www.jb51.cc/tag/zhuce/" target="_blank">注册</a>表中值的快照<a href="https://www.jb51.cc/tag/zhaiyao/" target="_blank">摘要</a>时。
* 有3种操作,每一种有4种形式,接受<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>包含keys,values,Entries,(key,value)参数的<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>.
* 因为ConcurrentHashMap的元素没有以任何特定的方式排序，并且可能在不同的并行执行中以不同的顺序处理，
* 所以提供的<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>的正确性不应取决于任何排序,及在过程中可能会瞬时改变的对象or值;除了forEach<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,其它<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>在理想情况下,* 应该是不会改变ConcurrentHashMap的.
* Map.Entry上的块操作<a href="https://www.jb51.cc/tag/buzhichi/" target="_blank">不支持</a><a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>setValue().
*
* forEach:对每个元素执行给定操作.
*
* search:返回在每个元素上应用给定<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>的第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>可用的非null元素;找到后不再进行后续的<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>.
*
* reduce:计算每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>元素.
* 设计的reduce<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>不能依赖元素顺序
*
* 批量操作可以接受<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>并行阈值参数p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold.
* 如果当前map的size预估值比给定的阈值小,则<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>顺序执行.
* 所以,如果给定阈值=Long.MAX_VALUE,则不会出现并行操作.
* 如果给定阈值=1,则会导致并行最大化,通过使用ForkJoinPool.commonPool()<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,对子任务分离.
* 通常情况下，您最初会选择这些极端值中的<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>，然后衡量使用中间开销与吞吐量之<a href="https://www.jb51.cc/tag/jiande/" target="_blank">间的</a>值的<a href="https://www.jb51.cc/tag/xingneng/" target="_blank">性能</a>。
*
* 批量操作的并发<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>来自ConcurrentHashMap的并发<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>：
* 插入,更新操作happens-before访问操作.
* 任何批量操作的结果反映了这些每元素关系的组成(但是，除非以某种方式知道它是静止的，否则就整个map而言，不一定是原子的）
* 相反，因为映射中的键和值永远不会为null，所以null作为当前缺少任何结果的可靠原子指标。
* 为了保持这个<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>，null作为所有非标量约简操作的隐含基础。
* 对于double，long和int版本，base应该与其他任何值结合时返回其他值（更正式地说，它应该是减少的标识元素）。
* 最常见的reduce<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>接口有这些<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>;例如,用MAX_VALUE或0或作为计算和的初始值。
*
* 作为参数提供的<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>和转换<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>应该类似地返回null来指示无结果（<a href="https://www.jb51.cc/tag/zaizhe/" target="_blank">在这</a>种情况下，它不被使用）
* 在映射的reduce<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>接口中,这也使得变换能够用作过滤器，如果元素不能合并,则返回null.
* 在search或者reduce操作中使用它们前,您可以通过在“null意味着现在没有”规则下自己组合它们来创建复合转换和过滤。
*
* 接受和/或返回Entry参数的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>维护键值关联.注意可以使用AbstractMap.SimpleEntry(k,v)作为空白entry参数.
*
* 批量操作可能会突然完成,从而引发<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a><a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>抛出异常.
* 请记住:在处理这样的异常时，其他并发执行的<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>也可能引发异常，或者即使第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>异常没有发生，其它异常也可能发生。
*
* 并行操作通常比顺序操作快,但不能保证一定是这样.
* 并行操作更慢的情况有:
* 1.如果并行计算的基础工作比计算本身更昂贵，那么小map上的并行操作可能比顺序形式执行更慢。
* 2.如果所有处理器都忙于执行不相关的任务，并行化可能无法实现太多的实际并行性。(无法形成流水线操作)
*
* <a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>序列化,<a href="https://www.jb51.cc/tag/buzhichi/" target="_blank">不支持</a>浅拷贝
*
* @since 1.5
* @author Doug Lea
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m <K> the type of keys maintained by this map
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m <V> the type of mapped values
*/
public class ConcurrentHashMap<K,V> extends AbstractMap<K,V>
implements ConcurrentMap<K,V>,Serializable {
private static final long serialVersionUID = 7249069246763182397L;
/*
* 概述:
*
* 这个散列表的主要设计目标是保持并发可读性（通常<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>get（），但也<a href="https://www.jb51.cc/tag/baokuo/" target="_blank">包括</a>迭代器和相关<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>），
* 同时最小化更新争用。次要目标是保持空间消耗与java.util.HashMap大致相同或更好，并支
* 持多线程在空表上较高的初始插入速率。
*
* 该映射通常用作分箱（分段）散列表。每个键值映射都保存在<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点中。大多数节点是具有散列，
* 键，值和下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>字段的基本节点类的实例。但是，存在各种子类：TreeNodes排列在平衡树中，而不是列表。
* TreeBins拥有TreeNodes集合的根。转发节点在调整大小期间放置在bin的头部。 ReservationNodes用作占位符，
* 同时在co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent和其它相关的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>中中建立值.
* 类型TreeBin，ForwardingNode和ReservationNode不包含普通的key，value或hash值，并且在<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>期间很容易
* 区分，因为它们具有负散列字段和空键和值字段。 （这些特殊节点要么不常见，要么是暂时的，所以携带一些未使用的
* 字段的影响是微不足道的。）
*
*
* 在第一次插入时，table大小被惰性初始化为2的整数次幂。表中的每个bin通常包含<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点列表（通常，列表只有零个或
* <a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点）。表访问需要volatile/atomic读，写和CAS<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>锁。因为在不<a href="https://www.jb51.cc/tag/zengjia/" target="_blank">增加</a>指针的情况这些操作无法实现，
* 所以我们使用内在<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>(sun.misc.Unsafe）操作。
*
* 我们使用节点散列字段的顶部（符号）位来进行控制 -- 由于地址限制，它无论如何都是可用的。具有负散列字段的节点是
* 被特别处理的,或者map<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>中直接被忽略.
*
* 向<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>空bin中插入节点是通过CAS完成的.在大多数key/hash分布中,这是一种很常见的put操作.其它的更新操作
* (insert,delete,update)都需要锁lock.因为如果每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin都分配<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>单独的lock会比较浪费存储空间,所以改为使用bin列表的
* 第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点本身作为锁。对这些锁的锁定<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>依赖于内置的“同步”监视器。
*
* 但是，使用列表的第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点作为锁本身并不足以满足：当<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点被锁定时，任何更新都必须首先验证它在锁定之后仍然是第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点，
* 如果不是，则重试.因为新节点总是追加到列表尾部，所以一旦节点首先进入<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>容器，它将保持第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>直到被<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>或容器变为无效（在调整大小时）。
*
* 每个分区都有锁的主要缺点是:由同<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>锁保护的分区列表中的其他节点上的其他更新操作可能会被延迟,比如equals()和映射等相关的<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>执行时,* 会花费很长时间.然而，<a href="https://www.jb51.cc/tag/tongji/" target="_blank">统计</a>上，在<a href="https://www.jb51.cc/tag/suiji/" target="_blank">随机</a>哈希码下，这不是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>常见问题。理想情况下,给定size的调整阈值为0.75,bin中节点的频率遵循平均
* 约为0.5的泊松分布,尽管调整size大小时泊松分布方差很大.忽略方差，列表大小k的预期出现是（exp（-0.5）* pow（0.5，k）/ factorial（k））。
* 第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>值是：
* 0: 0.60653066
* 1: 0.30326533
* 2: 0.07581633
* 3: 0.01263606
* 4: 0.00157952
* 5: 0.00015795
* 6: 0.00001316
* 7: 0.00000094
* 8: 0.00000006
* 其它值:只要是在10,000,000范围内,都会小于1.
*
* 两个线程访问同<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin中不同的元素的锁争用概率为:1 / (8 * #elements)
*
* 实际中遇到的哈希码分布有时会明显偏离均匀<a href="https://www.jb51.cc/tag/suiji/" target="_blank">随机</a>性。这<a href="https://www.jb51.cc/tag/baokuo/" target="_blank">包括</a>N>(1 << 30)的情况，所以一些key必然会出现碰撞。
* 因此，我们使用<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>二级策略，该策略适用于bin中节点数超过阈值的情况。这些TreeBins使用平衡树来保存节点（一种特殊形式的红黑树），
* 将<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>时间限制在O（log N).TreeBin中的每个<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>步骤至少比常规列表中的<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>步骤慢两倍，但考虑到N不能超过（1 << 64）（在内存地址
* 用完之前）,所以<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>步骤,锁的持有时间等等,都会受到限制,从而<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a>节点个数会控制在100个以内.TreeBin节点（TreeNodes）也保持与
* 常规节点相同的“下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>”遍历指针，所以可以以相同的方式在迭代器中遍历。
*
* 当table中元素个数超过百分比阈值（名义上为0.75，但请参见下文）时，会调整table的大小。
* 启动线程负责分配并设置替换数组,后续使用这个concurrentHashMap的其它线程在发现元素个数超过<a href="https://www.jb51.cc/tag/fuzai/" target="_blank">负载</a>因子规定大小时,都可以对table进行
* resize操作.TreeBins的使用保护了我们免于因过度resize带来的最坏影响.
* resize的过程是将旧table中的每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin都复制到新table的遍历复制过程.然而，线程要求在传输之前通过字段transferIndex传输小块索引，
* 从而减少争用。字段sizeCtl中的<a href="https://www.jb51.cc/tag/shengcheng/" target="_blank">生成</a>戳记确保重新定位不重叠。因为resize时,按照2的整数次幂进行扩容,所以每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin中的元素到达新的bin
* 后要么索引不变,要么产生2的次幂的位移.我们通过捕获旧节点可以重用的情况来消除不必要的节点创建，因为它们的下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>域不会改变.
* 平均而言,当tableresize时,只有1/6的节点需要进行clone.
* 被替换掉的节点只要不再被读线程引用,则会被GC回收.
* 元素都被转移到新table后,旧table的bin中只包含<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>转发节点(其hash域为MOVED),这一节点将新table作为它的key.在遇到转发节点时,查找
* 和更新操作会转到新table中重新执行.
*
* 每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin从旧table到新table的转移都需要<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>其bin的锁,这一过程中,可以阻止想要<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>这个bin的lock的线程进行等待.
* 但是其它线程可以加入协助resize的过程(这不是为了<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>锁),从而使得平均聚合等待时间变短.
* 转移还需要保证:无论是新table,还是旧table,只要是可访问的bin,都要保证其能进行遍历.
* 这部分是通过从最后<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin（table.length - 1）开始向第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>方向进行的。
* 在遇到转发节点时，遍历会移动到新table而无需重新访问节点。为了保证无序移动时也不跳过中间节点,在遍历期间首次遇到转发节点时会创建<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>
* 堆栈，以便在稍后处理当前table时保持其位置.对这些保存/恢复机制的需求相对较少，但是当遇到<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>转发节点时，通常会有更多的节点.
* 所以Traversers使用简单的缓存方案来避免创建这么多新的TableStack节点。
* 遍历方案也适用于部分遍历bin（通过<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>可选的Traverser构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>）来<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>分区聚合操作。
*
* 用到了表的延迟初始化
*
* 元素个数的count值由LongAdder来维护.通过对其特殊设置，避免使用LongAdder来访问导致创建多个CounterCell的隐式竞争检测.
* 计数器机制避免更新上的争用，但如果在并发访问期间读取频率太高，可能会遇到缓存抖动。为避免频繁读，仅在<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>到已拥有两个或更多节点的
* bin时尝试调整竞争大小。在统一的散列分布下，发生在阈值处的概率约为13％，这意味着只有大约1/8需要检查阈值（并且在调整大小之后，很少这
* 样做）。
*
* TreeBins的<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a>及与<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a>相关的操作都使用了一种特殊的比较形式(这也是为什么不能使用现有集合TreeMap的原因).TreeBins中包含的元素可能
* 在实现Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble上的原则不一样,所以对于它们之<a href="https://www.jb51.cc/tag/jiande/" target="_blank">间的</a>比较,则无法<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>Compar<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>()<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>.为了<a href="https://www.jb51.cc/tag/jiejue/" target="_blank">解决</a>这一问题,tree通过hash值对其排序.如果
* Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble.compar<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a> 可用的话,再用这个<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>对元素排序.在查找节点时，如果元素不具有可比性或比较为0,则可能需要对此节点对左右孩子
* 都进行<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a>.如果所有元素都不是可比较的并且具有相同的哈希值，则需要对全table进行扫描.
* 插入节点调整平衡时,为了保证总体有序,我们将类和identityHashCodes作为等同处理.
* 红黑树调整平衡的算法是对CLR算法的改进.
*
* TreeBins也需要额外的锁定机制。list更新过程中依旧可以进行遍历,但是红黑树在更新时却不能进行遍历,因为红黑树的调整可能会改变树的根节点,* 也可能改变各个节点之<a href="https://www.jb51.cc/tag/jiande/" target="_blank">间的</a>连接情况.TreeBins包含<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>简单的读写锁定机制，依赖于主要的同步策略：插入,<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>的结构调整会<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>lock机制;如果
* 在结构调整前有读操作,则必须读操作完成后,再进行结构的调整操作.由于只可能有<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>waiter,所以可以简单的使用<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>waiter域来阻止所有的写
* 操作.然后,读操作永远不需要被阻塞.如果保持根锁定，它们沿next指针遍历，直到锁定变为可用或列表遍历完为止.这类情况下并遍历不快，
* 但是可以最大限度地提高总预期吞吐量.
*
* 为了保持与以前的API和序列化兼容,这个类的版本引入了几个特别的<a href="https://www.jb51.cc/tag/neirong/" target="_blank">内容</a>:主要是:保留了构造器参数concurrencyLevel,但并未使用.
* 我们接受<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>loadFactor构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>参数，但只将它应用于初始表容量(这个参数的使用仅此一次).我们还声明了<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>未使用的“Segment”类，
* 它只在序列化时以最小的形式实例化。
*
* 另外，它扩展了AbstractMap,但这只是仅仅为了与这个类的以前版本兼容.
*
* ConcurrentHashMap<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>的组织顺序:
* 1.主要的静态声明+工具类
* 2.主要的public<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>
* 3.扩容<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,树,遍历器,批量操作.
*/
/* ---------------- 常量 -------------- */
/**
* table的最大容量.
* 为什么不是1<<32? 因为32位散列字段的前两位用于控制目的.
* 1<<30=1073741824
*/
private static final int MAXIMUM_CAPACITY = 1 << 30;
//<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认容量:16,和HashMap一样.
private static final int DEFAULT_CAPACITY = 16;
//数组最大长度,在toArray等相关<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>中用到
static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
//<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认并发级别,已经不再使用的字段,之所以还存在只是为了和之前的版本兼容.
private static final int DEFAULT_CONCURRENCY_LEVEL = 16;
//此表的加载因子。在构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>中重写此值只会影响初始表的容量,而不会使用实际的浮点值.
private static final float LOAD_FACTOR = 0.75f;
//<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>当前元素,bin中元素个数=8,则链表转为树
static final int TREEIFY_THRESHOLD = 8;
//bin中元素个数到达6个,则树转链表
static final int UNTREEIFY_THRESHOLD = 6;
//table转为树的阈值:64,此值最小为4*TREEIFY_THRESHOLD,显然,这里设定了64为初始值.
static final int MIN_TREEIFY_CAPACITY = 64;
//table扩容时,bin转移个数,最小为<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认的DEFAULT_CAPACITY=16.
//因为扩容时,可以多个线程同时操作,所以16个bin会被分配给多个的线程进行转移
private static final int MIN_TRANSFER_STRIDE = 16;
/**
* The number of bits used for generation stamp in sizeCtl.
* Must be at least 6 for 32bit arrays.
* 用来控制扩容,单线程进入的变量
* 32位数组时,最小值为6
*/
private static int RESIZE_STAMP_BITS = 16;
//resize时的线程最大个数
private static final int MAX_RESIZERS = (1 << (32 - RESIZE_STAMP_BITS)) - 1;
/**
* The bit shift for recording size stamp in sizeCtl.
* 用来控制扩容,单线程进入的变量
*/
private static final int RESIZE_STAMP_SHIFT = 32 - RESIZE_STAMP_BITS;
//节点hash域的编码
static final int MOVED = -1; // forwarding nodes的hash值
static final int TREEBIN = -2; // roots of trees的hash值
static final int RESERVED = -3; // transient reservations的hash值
static final int HASH_BITS = 0x7fffffff; // 正常散列节点的可用二进制位
//当前可用<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a><a href="https://www.jb51.cc/tag/shuliang/" target="_blank">数量</a>
static final int N<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a> = Runtime.getRuntime().availableProcessors();
//用于序列化兼容性
private static final ObjectStreamField[] serialPersistentFields = {
new ObjectStreamField("segments",Segment[].class),new ObjectStreamField("segmentMask",Integer.TYPE),new ObjectStreamField("segmentShift",Integer.TYPE)
};
/* ---------------- 节点 -------------- */
/**
* static内部类:最核心的内部类,包装了key-value条目.
* 特别注意:
* 1.<a href="https://www.jb51.cc/tag/buzhichi/" target="_blank">不支持</a>setValue<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>.
* 2.包含负数哈希值的node子类是特殊的,允许key和value为null.
* 3.ConcurrentHashMap不允许key和value为null
*/
static class Node<K,V> implements Map.Entry<K,V> {
final int hash;
final K key;
volatile V val;//比hashmap多了关键字volatile
volatile Node<K,V> next;//比hashmap多了关键字volatile
Node(int hash,K key,V val,Node<K,V> next) {
this.hash = hash;
this.key = key;
this.val = val;
this.next = next;
}
public final K getKey() { return key; }
public final V getValue() { return val; }
//entry的hash值=key和value的hash值求异或,和hashmap相同
public final int hashCode() { return key.hashCode() ^ val.hashCode(); }
public final String toString(){ return key + "=" + val; }
//本<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>不被<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>
public final V setValue(V value) {
throw new UnsupportedOperationException();
}
/**
* 检查步骤:
* 1.是Map.Entry类型
* 2.key和value都等价
*/
public final boolean equals(Object o) {
Object k,v,u; Map.Entry<?,?> e;
return ((o instanceof Map.Entry) &&
(k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
(v = e.getValue()) != null &&
(k == key || k.equals(key)) &&
(v == (u = val) || v.equals(u)));
}
//虚拟化<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>map.get（）;在子类中被覆盖。
Node<K,V> find(int h,Object k) {
Node<K,V> e = this;
if (k != null) {
do {
K ek;
if (e.hash == h &&
((ek = e.key) == k || (ek != null && k.equals(ek))))
return e;
} while ((e = e.next) != null);
}
return null;
}
}
/* ---------------- 静态工具 -------------- */
/**
* hash值无符号右移16位原因:
* 因为table使用的是2的整数次幂的掩码,仅在当前掩码之上的位上变化的散列集将会总是碰撞。(比如，Float键的集合在小table中保持连续的整数)
* 所以我们应用<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>转换，将高位的影响向下扩展。这是在速度,<a href="https://www.jb51.cc/tag/xingneng/" target="_blank">性能</a>,分布上做的<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>平衡.
* 因为许多常见的哈希集合已经合理分布(它们就不会在spread机制中受益)
* 因为我们已经使用了红黑树对bin中的大量碰撞做了处理,因此我们只是以最简单的方式做一些移位,然后进行异或运算，
* 以减少系统损失，并合并由于表边界而不会用于索引计算的最高位的影响(也就是&运算)。
*
*/
static final int spread(int h) {
return (h ^ (h >>> 16)) & HASH_BITS;//消除异或结果的最高位影响
}
/**
* 如果c为2的整数次幂,则返回c;
* 如果c不是2的整数次幂,则返回第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>比c大的2的整数次幂;
* eg:c=16,则返回结果为16;
* c=30,则返回结果为32;
*/
private static final int tableSi<a href="https://www.jb51.cc/tag/zef/" target="_blank">zef</a>or(int c) {
int n = c - 1;
n |= n >>> 1;
n |= n >>> 2;
n |= n >>> 4;
n |= n >>> 8;
n |= n >>> 16;
return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
}
//如果传入参数x实现了Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble接口,则返回类x,否则返回null.同HashMap
static Class<?> comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bleClassFor(Object x) {
if (x instanceof <a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble) {
Class<?> c; Type[] ts,as; Type t; P<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>meterizedType p;
if ((c = x.getClass()) == String.class) // bypass checks
return c;
if ((ts = c.getGenericInterfaces()) != null) {
for (int i = 0; i < ts.length; ++i) {
if (((t = ts[i]) instanceof P<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>meterizedType) &&
((p = (P<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>meterizedType)t).getRawType() ==
<a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble.class) &&
(as = p.getActualTypeArguments()) != null &&
as.length == 1 && as[0] == c) // type arg is c
return c;
}
}
}
return null;
}
//如果x和kc类型相同,则返回k.compar<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>(x)结果;否则返回0.同HashMap
@SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble
static int compareComp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bles(Class<?> kc,Object k,Object x) {
return (x == null || x.getClass() != kc ? 0 :
((<a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.Comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>ble)k).compar<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>(x));
}
/* ---------------- 访问table元素<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a> -------------- */
/*
* 下面3个<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,都是属于volatile类型的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,所以即使在resize的过程中,访问对table中的元素<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>的结果也是正确的.
* 针对tab参数,必须有非null判定.然后判定tab的长度是否>0,最后判定索引i是否合法.
* 注意:为了纠正<a href="https://www.jb51.cc/tag/yonghu/" target="_blank">用户</a>发生的任意并发<a href="https://www.jb51.cc/tag/cuowu/" target="_blank">错误</a>，这些检查必须对局部变量进行操作，这些检查必须对本地变量进行操作，这些变量占了下面一些特别的内联分配。
* 注意:对setTabAt()<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>的<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>总是发生在lock区域内,所以原则上不需要完整的volatile语义,但是目前的<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>还是保守地选择了volatile方式.
*/
@SuppressWarnings("unchecked")
static final <K,V> Node<K,V> tabAt(Node<K,V>[] tab,int i) {
return (Node<K,V>)U.g<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>bjectVolatile(tab,((long)i << ASHIFT) + ABASE);
}
static final <K,V> boolean casTabAt(Node<K,int i,V> c,V> v) {
return U.compareAndSwapObject(tab,((long)i << ASHIFT) + ABASE,c,v);
}
static final <K,V> void setTabAt(Node<K,V> v) {
U.putObjectVolatile(tab,v);
}
/* ---------------- 域 -------------- */
/**
* bin数组
* 延迟初始化到第一次插入元素.
* 数组长度总是2的整数次幂.
* 可以通过迭代器进行访问.
*/
transient volatile Node<K,V>[] table;
//resize时用到的临时table,只有在resize时,才不为null
private transient volatile Node<K,V>[] nextTable;
//基本计数器值，主要用于没有争用时，也可作为表初始化期<a href="https://www.jb51.cc/tag/jiande/" target="_blank">间的</a>后备。通过CAS更新。
private transient volatile long baseCount;
/**
* 用于控制table初始化和resize的<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>变量.
* 值为负数:table正在初始化or正在resize
* sizeCtl=-1:正在初始化;
* sizeCtl=-(1+n):当前有n个线程<a href="https://www.jb51.cc/tag/zhengzaijinxing/" target="_blank">正在进行</a>resize;
* 当table未初始化时，保存创建时使用的初始表大小，或<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认为0。初始化后，保存下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>要调整table大小的元素计数值。
*/
private transient volatile int sizeCtl;
//resize时,next table的索引+1,用于分割.
//nexttable索引[0,2*n-1],故transferIndex=n
private transient volatile int transferIndex;
//在调整大小和/或创建CounterCells时使用的自旋锁（通过CAS锁定）。
private transient volatile int cellsBusy;
//这是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>计数器数组,用于保存每个bin中节点个数.
private transient volatile CounterCell[] counterCells;
//视图views
private transient KeySetView<K,V> keySet;
private transient ValuesView<K,V> values;
private transient EntrySetView<K,V> entrySet;
/* ---------------- Public操作 -------------- */
/*-------------4个构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>-----------*/
//table<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认大小16
public ConcurrentHashMap() {
}
//初始化容量为:>=1.5*initialCapacity+1的最小2的整数次幂
public ConcurrentHashMap(int initialCapacity) {
if (initialCapacity < 0)
throw new IllegalArgumentException();
int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ?
MAXIMUM_CAPACITY :
tableSi<a href="https://www.jb51.cc/tag/zef/" target="_blank">zef</a>or(initialCapacity + (initialCapacity >>> 1) + 1));
this.sizeCtl = cap;
}
//创建<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>和输入参数map映射一样的map
public ConcurrentHashMap(Map<? extends K,? extends V> m) {
this.sizeCtl = DEFAULT_CAPACITY;
putAll(m);
}
public ConcurrentHashMap(int initialCapacity,float loadFactor) {
this(initialCapacity,loadFactor,1);
}
public ConcurrentHashMap(int initialCapacity,float loadFactor,int concurrencyLevel) {
if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0)
throw new Ille<a href="https://www.jb51.cc/tag/gal/" target="_blank">gal</a>ArgumentException();
if (initialCapacity < concurrencyLevel) // Use at least as many bins
initialCapacity = concurrencyLevel; // as estimated threads
long size = (long)(1.0 + (long)initialCapacity / loadFactor);
//如果initialCapacity=16,则cap=32;
int cap = (size >= (long)MAXIMUM_CAPACITY) ?
MAXIMUM_CAPACITY : tableSi<a href="https://www.jb51.cc/tag/zef/" target="_blank">zef</a>or((int)size);
this.sizeCtl = cap;
}
// Original (since JDK1.2) Map methods
public int size() {
//节点总数n
long n = sumCount();
return ((n < 0L) ? 0 :
(n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE :
(int)n);
}
public boolean isEmpty() {
return sumCount() <= 0L; // ig<a href="https://www.jb51.cc/tag/nor/" target="_blank">nor</a>e transient negative values
}
public V get(Object key) {
Node<K,V>[] tab; Node<K,V> e,p; int n,eh; K ek;
//根据hash值查找散列位置
int h = spread(key.hashCode());
if ((tab = table) != null && (n = tab.length) > 0 &&
(e = tabAt(tab,(n - 1) & h)) != null) {
//如果tab[(n-1)&h]处的节点就是要查找的节点
if ((eh = e.hash) == h) {
if ((ek = e.key) == key || (ek != null && key.equals(ek)))
return e.val;
}
//如果是树节点
else if (eh < 0)
return (p = e.find(h,key)) != null ? p.val : null;
//如果是链表节点
while ((e = e.next) != null) {
if (e.hash == h &&
((ek = e.key) == key || (ek != null && key.equals(ek))))
return e.val;
}
}
return null;
}
//<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>上面的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>
public boolean containsKey(Object key) {
return get(key) != null;
}
public boolean containsValue(Object value) {
if (value == null)
throw new NullPointerException();
Node<K,V>[] t;
if ((t = table) != null) {
Traverser<K,V> it = new Traverser<K,V>(t,t.length,t.length);
for (Node<K,V> p; (p = it.advance()) != null; ) {
V v;
if ((v = p.val) == value || (v != null && value.equals(v)))
return true;
}
}
return false;
}
//key,value不能为null
public V put(K key,V value) {
return putVal(key,value,false);
}
/** Implementation for put and putIfAbsent
* 总体步骤:
* 1.判定key,value合法性
* 2.插入位置为空bin
* 3.插入位置<a href="https://www.jb51.cc/tag/zhengzaijinxing/" target="_blank">正在进行</a>resize
* 4.插入位置在table中,且该位置未进行resize
* 5.插入完成后,判定bin中节点个数是否>=8,从而决定是否进行链表转红黑树.
*
*/
final V putVal(K key,V value,boolean onlyIfAbsent) {
if (key == null || value == null) throw new NullPointerException();
//<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>hash值
int hash = spread(key.hashCode());
int binCount = 0;
for (Node<K,V>[] tab = table;;) {
Node<K,V> f; int n,i,fh;
if (tab == null || (n = tab.length) == 0)
tab = initTable();
//如果插入位置为空的bin
else if ((f = tabAt(tab,i = (n - 1) & hash)) == null) {
if (casTabAt(tab,null,new Node<K,V>(hash,key,null)))
break; // no lock when adding to empty bin
}
//如果查找位置为forwarding node
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
//在当前table中查找插入位置
else {
V oldVal = null;
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块,保证插入安全
synchronized (f) {
if (tabAt(tab,i) == f) {
//如果为链表
if (fh >= 0) {
binCount = 1;
for (Node<K,V> e = f;; ++binCount) {
K ek;
//找到,更新值
if (e.hash == hash &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
oldVal = e.val;
if (!onlyIfAbsent)
e.val = value;
break;
}
Node<K,V> pred = e;
if ((e = e.next) == null) {
pred.next = new Node<K,null);
break;
}
}
}
//如果为红黑树
else if (f instanceof TreeBin) {
Node<K,V> p;
binCount = 2;
if ((p = ((TreeBin<K,V>)f).putTreeVal(hash,value)) != null) {
oldVal = p.val;
if (!onlyIfAbsent)
p.val = value;
}
}
}
}
//插入节点后,检查bin中节点个数是否>=8,如果大于,则由链表转为红黑树
if (binCount != 0) {
if (binCount >= TREEIFY_THRESHOLD)
treeifyBin(tab,i);
if (oldVal != null)
return oldVal;
break;
}
}
}
addCount(1L,binCount);
return null;
}
public void putAll(Map<? extends K,? extends V> m) {
//对table的size进行设置,使得其可以容纳新加入的元素.
tryPresize(m.size());
for (Map.Entry<? extends K,? extends V> e : m.entrySet())
putVal(e.getKey(),e.getValue(),false);
}
public V remove(Object key) {
return replaceNode(key,null);
}
//此<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>是对4个公有<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>remove/replace的辅助<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>.
final V replaceNode(Object key,Object cv) {
int hash = spread(key.hashCode());
for (Node<K,fh;
//空表or查找位置bin为null
if (tab == null || (n = tab.length) == 0 ||
(f = tabAt(tab,i = (n - 1) & hash)) == null)
break;
//如果查找节点为转移节点forwarding node
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
else {
V oldVal = null;
boolean validated = false;
//同步代码块,保证删除安全性
synchronized (f) {
if (tabAt(tab,i) == f) {
//bin为链表结构
if (fh >= 0) {
validated = true;
for (Node<K,V> e = f,pred = null;;) {
K ek;
if (e.hash == hash &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
V ev = e.val;
if (cv == null || cv == ev ||
(ev != null && cv.equals(ev))) {
oldVal = ev;
if (value != null)
e.val = value;
else if (pred != null)
pred.next = e.next;
else
setTabAt(tab,e.next);
}
break;
}
//记录上<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>访问节点
pred = e;
//更新e为下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点
if ((e = e.next) == null)
break;
}
}
//bin为红黑树结构
else if (f instanceof TreeBin) {
validated = true;
TreeBin<K,V> t = (TreeBin<K,V>)f;
TreeNode<K,V> r,p;
if ((r = t.root) != null &&
(p = r.findTreeNode(hash,null)) != null) {
V pv = p.val;
if (cv == null || cv == pv ||
(pv != null && cv.equals(pv))) {
oldVal = pv;
if (value != null)
p.val = value;
else if (t.removeTreeNode(p))
setTabAt(tab,untreeify(t.f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t));
}
}
}
}
}
if (validated) {
if (oldVal != null) {
if (value == null)
//更新节点个数
addCount(-1L,-1);
return oldVal;
}
break;
}
}
}
return null;
}
public void clear() {
long delta = 0L; // negative number of deletions
int i = 0;
Node<K,V>[] tab = table;
while (tab != null && i < tab.length) {
int fh;
Node<K,V> f = tabAt(tab,i);
if (f == null)
++i;
//如果节点为转移节点forwarding node
else if ((fh = f.hash) == MOVED) {
tab = helpTransfer(tab,f);
i = 0; // restart
}
else {
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块,<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>i位置处的节点
synchronized (f) {
if (tabAt(tab,i) == f) {
Node<K,V> p = (fh >= 0 ? f :
(f instanceof TreeBin) ?
((TreeBin<K,V>)f).f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t : null);
while (p != null) {
--delta;
p = p.next;
}
setTabAt(tab,i++,null);
}
}
}
}
if (delta != 0L)
addCount(delta,-1);
}
public KeySetView<K,V> keySet() {
KeySetView<K,V> ks;
return (ks = keySet) != null ? ks : (keySet = new KeySetView<K,V>(this,null));
}
public Collection<V> values() {
ValuesView<K,V> vs;
return (vs = values) != null ? vs : (values = new ValuesView<K,V>(this));
}
public Set<Map.Entry<K,V>> entrySet() {
EntrySetView<K,V> es;
return (es = entrySet) != null ? es : (entrySet = new EntrySetView<K,V>(this));
}
//返回map的hash值.
//结果=sum(key.hashCode() ^ value.hashCode())
public int hashCode() {
int h = 0;
Node<K,V> p; (p = it.advance()) != null; )
h += p.key.hashCode() ^ p.val.hashCode();
}
return h;
}
//格式:{key1=value1,key2=value2,...}
public String toString() {
Node<K,V>[] t;
int f = (t = table) == null ? 0 : t.length;
Traverser<K,f,f);
StringBuilder sb = new StringBuilder();
sb.append('{');
Node<K,V> p;
if ((p = it.advance()) != null) {
for (;;) {
K k = p.key;
V v = p.val;
sb.append(k == this ? "(this Map)" : k);
sb.append('=');
sb.append(v == this ? "(this Map)" : v);
if ((p = it.advance()) == null)
break;
sb.append(',').append(' ');
}
}
return sb.append('}').toString();
}
/**
* Compares the specified object with this map for equality.
* Returns {@code true} if the given object is a map with the same
* mappings as this map. This operation may return misleading
* results if either map is concurrently modified during execution
* of this method.
*
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m o object to be compared for equality with this map
* @return {@code true} if the specified object is equal to this map
*/
public boolean equals(Object o) {
//内存地址是否相同
if (o != this) {
//是否为map类型
if (!(o instanceof Map))
return false;
//类型转化
Map<?,?> m = (Map<?,?>) o;
Node<K,V>[] t;
//记录table长度
int f = (t = table) == null ? 0 : t.length;
Traverser<K,f);
//遍历table,检查和o的value一致性
for (Node<K,V> p; (p = it.advance()) != null; ) {
V val = p.val;
Object v = m.get(p.key);
if (v == null || (v != val && !v.equals(val)))
return false;
}
//遍历o,检查自身key和value的合法性
for (Map.Entry<?,?> e : m.entrySet()) {
Object mk,mv,v;
if ((mk = e.getKey()) == null ||
(mv = e.getValue()) == null ||
(v = get(mk)) == null ||
(mv != v && !mv.equals(v)))
return false;
}
}
return true;
}
//旧版本中使用的类,存在的意义:序列化兼容性
static class Segment<K,V> extends <a href="https://www.jb51.cc/tag/reentrantlock/" target="_blank">reentrantlock</a> implements Serializable {
private static final long serialVersionUID = 2249069246763182397L;
final float loadFactor;
Segment(float lf) { this.loadFactor = lf; }
}
//用于序列化:将concurrenthashmap写入stream中.
private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException {
// 用于序列化版本兼容
// Emulate segment cal<a href="https://www.jb51.cc/tag/cula/" target="_blank">cula</a>tion from prev<a href="https://www.jb51.cc/tag/IoU/" target="_blank">IoU</a>s version of this class
int sshift = 0;
int ssize = 1;
while (ssize < DEFAULT_CONCURRENCY_LEVEL) {
++sshift;
ssize <<= 1;
}
int segmentShift = 32 - sshift;
int segmentMask = ssize - 1;
@SuppressWarnings("unchecked")
Segment<K,V>[] segments = (Segment<K,V>[])
new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL];
for (int i = 0; i < segments.length; ++i)
segments[i] = new Segment<K,V>(LOAD_FACTOR);
s.putFields().put("segments",segments);
s.putFields().put("segmentShift",segmentShift);
s.putFields().put("segmentMask",segmentMask);
s.writeFields();
Node<K,V> p; (p = it.advance()) != null; ) {
s.writeObject(p.key);
s.writeObject(p.val);
}
}
s.writeObject(null);
s.writeObject(null);
segments = null; // throw away
}
private void rea<a href="https://www.jb51.cc/tag/dob/" target="_blank">dob</a>ject(java.io.ObjectInputStream s)
throws java.io.IOException,ClassNotFoundException {
/*
* 为了在典型情况下提高<a href="https://www.jb51.cc/tag/xingneng/" target="_blank">性能</a>，我们在读取时创建节点，然后在知道大小后放置在表中.
* 但是，我们还必须验证唯一性并处理过多的bin，这需要putVal机制的专用版本
*/
sizeCtl = -1; // force exclusion for table construction
s.defaultRea<a href="https://www.jb51.cc/tag/dob/" target="_blank">dob</a>ject();
long size = 0L;
Node<K,V> p = null;
for (;;) {
@SuppressWarnings("unchecked")
K k = (K) s.rea<a href="https://www.jb51.cc/tag/dob/" target="_blank">dob</a>ject();
@SuppressWarnings("unchecked")
V v = (V) s.rea<a href="https://www.jb51.cc/tag/dob/" target="_blank">dob</a>ject();
if (k != null && v != null) {
p = new Node<K,V>(spread(k.hashCode()),k,p);
++size;
}
else
break;
}
if (size == 0L)
sizeCtl = 0;
else {
int n;
if (size >= (long)(MAXIMUM_CAPACITY >>> 1))
n = MAXIMUM_CAPACITY;
else {
int sz = (int)size;
n = tableSi<a href="https://www.jb51.cc/tag/zef/" target="_blank">zef</a>or(sz + (sz >>> 1) + 1);
}
@SuppressWarnings("unchecked")
Node<K,V>[] tab = (Node<K,V>[])new Node<?,?>[n];
int mask = n - 1;
long added = 0L;
while (p != null) {
boolean insertAtFront;
Node<K,V> next = p.next,f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
int h = p.hash,j = h & mask;
if ((f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t = tabAt(tab,j)) == null)
insertAtFront = true;
else {
K k = p.key;
if (f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t.hash < 0) {
TreeBin<K,V>)f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
if (t.putTreeVal(h,p.val) == null)
++added;
insertAtFront = false;
}
else {
int binCount = 0;
insertAtFront = true;
Node<K,V> q; K qk;
for (q = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t; q != null; q = q.next) {
if (q.hash == h &&
((qk = q.key) == k ||
(qk != null && k.equals(qk)))) {
insertAtFront = false;
break;
}
++binCount;
}
if (insertAtFront && binCount >= TREEIFY_THRESHOLD) {
insertAtFront = false;
++added;
p.next = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
TreeNode<K,V> hd = null,tl = null;
for (q = p; q != null; q = q.next) {
TreeNode<K,V> t = new TreeNode<K,V>
(q.hash,q.key,q.val,null);
if ((t.prev = tl) == null)
hd = t;
else
tl.next = t;
tl = t;
}
setTabAt(tab,j,new TreeBin<K,V>(hd));
}
}
}
if (insertAtFront) {
++added;
p.next = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
setTabAt(tab,p);
}
p = next;
}
table = tab;
sizeCtl = n - (n >>> 2);
baseCount = added;
}
}
/*-------ConcurrentMap<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>---------*/
//存在,替换,返回旧value;否则不操作,返回null
public V putIfAbsent(K key,true);
}
public boolean remove(Object key,Object value) {
if (key == null)
throw new NullPointerException();
return value != null && replaceNode(key,value) != null;
}
public boolean replace(K key,V oldValue,V newValue) {
if (key == null || oldValue == null || newValue == null)
throw new NullPointerException();
return replaceNode(key,newValue,oldValue) != null;
}
public V replace(K key,V value) {
if (key == null || value == null)
throw new NullPointerException();
return replaceNode(key,null);
}
/*--------Overrides在JDK8中Map接口扩展的<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>--------*/
//key有value,则返回value;
//否则返回参数值
public V g<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>rDefault(Object key,V defaultValue) {
V v;
return (v = get(key)) == null ? defaultValue : v;
}
public void forEach(BiConsumer<? super K,? super V> action) {
if (action == null) throw new NullPointerException();
Node<K,V> p; (p = it.advance()) != null; ) {
action.accept(p.key,p.val);
}
}
}
public void replaceAll(BiFunction<? super K,? super V,? extends V> function) {
if (function == null) throw new NullPointerException();
Node<K,V> p; (p = it.advance()) != null; ) {
V oldValue = p.val;
for (K key = p.key;;) {
V newValue = function.apply(key,oldValue);
if (newValue == null)
throw new NullPointerException();
if (replaceNode(key,oldValue) != null ||
(oldValue = get(key)) == null)
break;
}
}
}
}
/**
* 如果指定的键尚未与值关联，则尝试使用给定的映射<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>计算其值，并将其输入到该映射中，除非是null.
* 整个<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a><a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>是以原子方式执行的，因此每个键最多应用一次该<a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>。
* 在进行计算时，其他线程在此映射上的某些尝试更新操作可能会被阻止，因此计算应该简短并且不要尝试更新此map中的任何其他映射。
*/
public V co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent(K key,Function<? super K,? extends V> mappingFunction) {
if (key == null || mappingFunction == null)
throw new NullPointerException();
int h = spread(key.hashCode());
V val = null;
int binCount = 0;
for (Node<K,fh;
if (tab == null || (n = tab.length) == 0)
tab = initTable();
//不存在
else if ((f = tabAt(tab,i = (n - 1) & h)) == null) {
Node<K,V> r = new ReservationNode<K,V>();
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块,计算新值并插入map
synchronized (r) {
if (casTabAt(tab,r)) {
binCount = 1;
Node<K,V> node = null;
try {
if ((val = mappingFunction.apply(key)) != null)
node = new Node<K,V>(h,val,null);
} finally {
setTabAt(tab,node);
}
}
}
if (binCount != 0)
break;
}
//此节点为转移节点forwarding node
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
//存在,且不是转移节点
else {
boolean added = false;
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块:分链表和红黑树两种情况进行插入
synchronized (f) {
if (tabAt(tab,i) == f) {
if (fh >= 0) {
binCount = 1;
for (Node<K,V> e = f;; ++binCount) {
K ek; V ev;
if (e.hash == h &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
val = e.val;
break;
}
Node<K,V> pred = e;
if ((e = e.next) == null) {
if ((val = mappingFunction.apply(key)) != null) {
added = true;
pred.next = new Node<K,null);
}
break;
}
}
}
else if (f instanceof TreeBin) {
binCount = 2;
TreeBin<K,p;
if ((r = t.root) != null &&
(p = r.findTreeNode(h,null)) != null)
val = p.val;
else if ((val = mappingFunction.apply(key)) != null) {
added = true;
t.putTreeVal(h,val);
}
}
}
}
//插入后,判定是否需要将链表转为红黑树
if (binCount != 0) {
if (binCount >= TREEIFY_THRESHOLD)
treeifyBin(tab,i);
if (!added)
return val;
break;
}
}
}
//<a href="https://www.jb51.cc/tag/zengjia/" target="_blank">增加</a>节点个数
if (val != null)
addCount(1L,binCount);
return val;
}
/**
* 如果指定的键尚已经与值关联，则尝试使用给定的映射<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>计算其值，并更改该映射.
* 整个<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a><a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>是以原子方式执行的，因此每个键最多应用一次该<a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>。
* 在进行计算时，其他线程在此映射上的某些尝试更新操作可能会被阻止，因此计算应该简短并且不要尝试更新此map中的任何其他映射。
*/
public V co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfPresent(K key,BiFunction<? super K,? extends V> remappingFunction) {
if (key == null || remappingFunction == null)
throw new NullPointerException();
int h = spread(key.hashCode());
V val = null;
int delta = 0;
int binCount = 0;
for (Node<K,fh;
if (tab == null || (n = tab.length) == 0)
tab = initTable();
//如果为null,返回
else if ((f = tabAt(tab,i = (n - 1) & h)) == null)
break;
//如果为转移节点,帮助转移
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
//计算值并替换
else {
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块,分链表和红黑树节点讨论插入.
synchronized (f) {
if (tabAt(tab,pred = null;; ++binCount) {
K ek;
if (e.hash == h &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
val = remappingFunction.apply(key,e.val);
if (val != null)
e.val = val;
else {
delta = -1;
Node<K,V> en = e.next;
if (pred != null)
pred.next = en;
else
setTabAt(tab,en);
}
break;
}
pred = e;
if ((e = e.next) == null)
break;
}
}
else if (f instanceof TreeBin) {
binCount = 2;
TreeBin<K,null)) != null) {
val = remappingFunction.apply(key,p.val);
if (val != null)
p.val = val;
else {
delta = -1;
if (t.removeTreeNode(p))
setTabAt(tab,untreeify(t.first));
}
}
}
}
}
if (binCount != 0)
break;
}
}
if (delta != 0)
addCount((long)delta,binCount);
return val;
}
//指定key如果没有value,则为其计算一个value
public V compute(K key,fh;
//如果表为null,则初始化表
if (tab == null || (n = tab.length) == 0)
tab = initTable();
//如果指定位置为null
else if ((f = tabAt(tab,V>();
//同步<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块:为其计算值,并插入map
synchronized (r) {
if (casTabAt(tab,V> node = null;
try {
if ((val = remappingFunction.apply(key,null)) != null) {
delta = 1;
node = new Node<K,null);
}
} finally {
//插入map
setTabAt(tab,node);
}
}
}
if (binCount != 0)
break;
}
//如果指定位置为转移节点,当前线程转去帮忙转移节点
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
//同步代码块
else {
synchronized (f) {
if (tabAt(tab,i) == f) {
//链表节点
if (fh >= 0) {
binCount = 1;
for (Node<K,e.val);
//计算的value不为null,更改原value
if (val != null)
e.val = val;
//计算的value为null
else {
delta = -1;
Node<K,V> en = e.next;
//上<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点为为null,<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>当前节点
if (pred != null)
pred.next = en;
//上<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点为null
else
setTabAt(tab,en);
}
break;
}
pred = e;
if ((e = e.next) == null) {
val = remappingFunction.apply(key,null);
if (val != null) {
delta = 1;
pred.next =
new Node<K,null);
}
break;
}
}
}
//红黑树树节点
else if (f instanceof TreeBin) {
binCount = 1;
TreeBin<K,p;
if ((r = t.root) != null)
p = r.findTreeNode(h,null);
else
p = null;
V pv = (p == null) ? null : p.val;
val = remappingFunction.apply(key,pv);
if (val != null) {
if (p != null)
p.val = val;
else {
delta = 1;
t.putTreeVal(h,val);
}
}
else if (p != null) {
delta = -1;
if (t.removeTreeNode(p))
setTabAt(tab,untreeify(t.first));
}
}
}
}
if (binCount != 0) {
if (binCount >= TREEIFY_THRESHOLD)
treeifyBin(tab,i);
break;
}
}
}
if (delta != 0)
addCount((long)delta,binCount);
return val;
}
/**
* 如果指定的键尚未与（非空）值相关联，则将其与给定值value相关联。
* 否则，将该值替换为给定的重映射<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>的结果，或者如果为null则被移除.
* 整个<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a><a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>是以原子方式执行的。其他线程在此映射上的某些尝试更新操作可能会被阻止当计算<a href="https://www.jb51.cc/tag/zhengzaijinxing/" target="_blank">正在进行</a>时，所以计算应该简短，
* 并且不能尝试更新此Map的任何其他映射。
*/
public V merge(K key,BiFunction<? super V,? extends V> remappingFunction) {
if (key == null || value == null || remappingFunction == null)
throw new NullPointerException();
int h = spread(key.hashCode());
V val = null;
int delta = 0;
int binCount = 0;
for (Node<K,fh;
//如果tab为null,初始化table
if (tab == null || (n = tab.length) == 0)
tab = initTable();
//如果该散列位置没有元素,为null
else if ((f = tabAt(tab,i = (n - 1) & h)) == null) {
//利用CAS为索引i处节点赋值
if (casTabAt(tab,null))) {
delta = 1;
val = value;
break;
}
}
//如果table在进行resize,则当前线程帮忙去resize
else if ((fh = f.hash) == MOVED)
tab = helpTransfer(tab,f);
//如果散列位置有数值
else {
//同步代码块:
synchronized (f) {
//查找i处的节点
if (tabAt(tab,i) == f) {
//如果为链表节点
if (fh >= 0) {
binCount = 1;
for (Node<K,pred = null;; ++binCount) {
K ek;
if (e.hash == h &&
((ek = e.key) == key ||
(ek != null && key.equals(ek)))) {
val = remappingFunction.apply(e.val,value);
if (val != null)
e.val = val;
else {
delta = -1;
Node<K,V> en = e.next;
if (pred != null)
pred.next = en;
//原value=新value=null,则<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>当前节点
else
setTabAt(tab,en);
}
break;
}
pred = e;
if ((e = e.next) == null) {
delta = 1;
val = value;
pred.next =
new Node<K,null);
break;
}
}
}
//如果节点为红黑树节点
else if (f instanceof TreeBin) {
binCount = 2;
TreeBin<K,V> r = t.root;
TreeNode<K,V> p = (r == null) ? null :
r.findTreeNode(h,null);
val = (p == null) ? value :
remappingFunction.apply(p.val,value);
if (val != null) {
if (p != null)
p.val = val;
else {
delta = 1;
t.putTreeVal(h,binCount);
return val;
}
/*-----------Hashtable的传统<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>------------*/
//此<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>在<a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>上与containsValue（Object）完全相同
public boolean contains(Object value) {
return containsValue(value);
}
//返回key的枚举
public Enumeration<K> keys() {
Node<K,V>[] t;
int f = (t = table) == null ? 0 : t.length;
return new KeyI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,this);
}
//返回value的枚举
public Enumeration<V> elements() {
Node<K,V>[] t;
int f = (t = table) == null ? 0 : t.length;
return new ValueI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,this);
}
/*-----------ConcurrentHashMap-only methods------独有<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>------------*/
/**
* 返回映射的<a href="https://www.jb51.cc/tag/shuliang/" target="_blank">数量</a>。
* 求映射个数时,应该使用此<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>而不是size()<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>，因为ConcurrentHashMap包含映射个数可以比Integer.MAX_VALUE更多。
* 注意:本<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>返回的值是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>估计值;如果并发插入或<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>，实际计数可能会有所不同。
* @return the number of mappings
* @since 1.8
*/
public long mappingCount() {
long n = sumCount();
return (n < 0L) ? 0L : n; // ig<a href="https://www.jb51.cc/tag/nor/" target="_blank">nor</a>e transient negative values
}
/**
* 根据给定类型Boolean.TRUE,新建<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>Set,当然这个set也是由ConcurrentHashMap作为后备支撑的
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m <K> the element type of the returned set
* @return the new set
* @since 1.8
*/
public static <K> KeySetView<K,Boolean> newKeySet() {
return new KeySetView<K,Boolean>
(new ConcurrentHashMap<K,Boolean>(),Boolean.TRUE);
}
/**
* @since 1.8
*/
public static <K> KeySetView<K,Boolean> newKeySet(int initialCapacity) {
return new KeySetView<K,Boolean>(initialCapacity),Boolean.TRUE);
}
//根据给定的通用value,在add,addAll<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>中可以随意<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>值.这当然只适用于从该视图中为所有<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>使用相同值的情况。
public KeySetView<K,V> keySet(V mappedValue) {
if (mappedValue == null)
throw new NullPointerException();
return new KeySetView<K,mappedValue);
}
/* ---------------- Special Nodes 特殊节点 -------------- */
/**
* <a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>用于连接两个table的节点类。它包含<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>nextTable指针，用于指向下一张表。而且这个节点的key,next指针全部为null，
* 它的hash值为-1. 这里面定义的find的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>是从nextTable里进行<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a>节点，而不是以自身为头节点进行查找
*/
static final class ForwardingNode<K,V> extends Node<K,V> {
final Node<K,V>[] nextTable;
ForwardingNode(Node<K,V>[] tab) {
//hash值=MOVED=-1
super(MOVED,null);
this.nextTable = tab;
}
Node<K,Object k) {
// loop to avoid arbitrarily deep recursion on forwarding nodes
//循环以避免转发节点上的任意深度递归
outer: for (Node<K,V>[] tab = nextTable;;) {
Node<K,V> e; int n;
//如果table为null,or长度为0,or指定bin无元素
if (k == null || tab == null || (n = tab.length) == 0 ||
(e = tabAt(tab,(n - 1) & h)) == null)
return null;
//循环
for (;;) {
int eh; K ek;
if ((eh = e.hash) == h &&
((ek = e.key) == k || (ek != null && k.equals(ek))))
return e;
//哈希值<0
if (eh < 0) {
//如果是转发节点
if (e instanceof ForwardingNode) {
//更新查找到新table
tab = ((ForwardingNode<K,V>)e).nextTable;
continue outer;
}
//非转发节点,则直接查找
else
return e.find(h,k);
}
if ((e = e.next) == null)
return null;
}
}
}
}
//在co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent和co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>中的节点占位符
static final class ReservationNode<K,V> {
ReservationNode() {
super(RESERVED,null);
}
Node<K,Object k) {
return null;
}
}
/* ---------------- Table 初始化 and Resizing -------------- */
//返回用于调整大小为n的table的<a href="https://www.jb51.cc/tag/biaoji/" target="_blank">标记</a>位。左移RESIZE_STAMP_SHIFT二进制位时,数值必为负.
static final int resizeStamp(int n) {
return Integer.numberOfLeadingZeros(n) | (1 << (RESIZE_STAMP_BITS - 1));
}
//使用sizeCtl中记录的size值初始化table
//对于ConcurrentHashMap来说，<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>它的构造<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>仅仅是设置了一些参数而已。
//而整个table的初始化是在向ConcurrentHashMap中插入元素的时候发生的。
private final Node<K,V>[] initTable() {
Node<K,V>[] tab; int sc;
while ((tab = table) == null || tab.length == 0) {
//如果当前有线程在对table进行初始化,则当前线程被阻塞,这也可以看出ConcurrentHashMap的初始化只能由<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>线程完成.
if ((sc = sizeCtl) < 0)
Thread.yield(); // 初始化失败,进行自旋
//利用CAS方法把sizectl的值置为-1,防止其他线程进入,表示本线程正在进行初始化
else if (U.compareAndSwapInt(this,SIZECTL,sc,-1)) {
try {
if ((tab = table) == null || tab.length == 0) {
int n = (sc > 0) ? sc : DEFAULT_CAPACITY;
//初始化大小为n的node数组
@SuppressWarnings("unchecked")
Node<K,V>[] nt = (Node<K,?>[n];
table = tab = nt;
sc = n - (n >>> 2);////相当于0.75*n 设置<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>扩容的阈值
}
} finally {
sizeCtl = sc;//sizeCtl的值改为0.75*n
}
break;
}
}
return tab;
}
/**
* <a href="https://www.jb51.cc/tag/zengjia/" target="_blank">增加</a>节点个数，如果table太小而没有resize，则检查是否需要resize。如果已经调整大小，则可以帮助复制转移节点。转移后重新检查占用情况，
* 以确定是否还需要调整大小，因为resize总是比put操作滞后。
*/
private final void addCount(long x,int check) {
CounterCell[] as; long b,s;
if ((as = counterCells) != null ||
!U.compareAndSwapLong(this,BASECOUNT,b = baseCount,s = b + x)) {
CounterCell a; long v; int m;
boolean uncontended = true;
if (as == null || (m = as.length - 1) < 0 ||
(a = as[ThreadLocalRandom.getProbe() & m]) == null ||
!(uncontended =
U.compareAndSwapLong(a,CELLVALUE,v = a.value,v + x))) {
fullAddCount(x,uncontended);
return;
}
if (check <= 1)
return;
s = sumCount();
}
if (check >= 0) {
Node<K,nt; int n,sc;
while (s >= (long)(sc = sizeCtl) && (tab = table) != null &&
(n = tab.length) < MAXIMUM_CAPACITY) {
int rs = resizeStamp(n);
if (sc < 0) {
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
sc == rs + MAX_RESIZERS || (nt = nextTable) == null ||
transferIndex <= 0)
break;
if (U.compareAndSwapInt(this,sc + 1))
transfer(tab,nt);
}
else if (U.compareAndSwapInt(this,(rs << RESIZE_STAMP_SHIFT) + 2))
transfer(tab,null);
s = sumCount();
}
}
}
//如果resize<a href="https://www.jb51.cc/tag/zhengzaijinxing/" target="_blank">正在进行</a>,则多个线程帮助节点的复制操作.
final Node<K,V>[] helpTransfer(Node<K,V> f) {
Node<K,V>[] nextTab; int sc;
//如果tab不为null,且f为转移节点,且新table不为null
if (tab != null && (f instanceof ForwardingNode) &&
(nextTab = ((ForwardingNode<K,V>)f).nextTable) != null) {
//返回resize后的table的<a href="https://www.jb51.cc/tag/biaoji/" target="_blank">标记</a>位
int rs = resizeStamp(tab.length);
while (nextTab == nextTable && table == tab &&
(sc = sizeCtl) < 0) {
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
sc == rs + MAX_RESIZERS || transferIndex <= 0)
break;
if (U.compareAndSwapInt(this,sc + 1)) {
transfer(tab,nextTab);
break;
}
}
return nextTab;
}
return table;
}
//尝试将table大小设定为:1.5*size+1,以容纳元素
private final void tryPresize(int size) {
int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :
tableSi<a href="https://www.jb51.cc/tag/zef/" target="_blank">zef</a>or(size + (size >>> 1) + 1);
int sc;
while ((sc = sizeCtl) >= 0) {
Node<K,V>[] tab = table; int n;
if (tab == null || (n = tab.length) == 0) {
n = (sc > c) ? sc : c;
if (U.compareAndSwapInt(this,-1)) {
try {
if (table == tab) {
@SuppressWarnings("unchecked")
Node<K,?>[n];
table = nt;
sc = n - (n >>> 2);
}
} finally {
sizeCtl = sc;
}
}
}
else if (c <= sc || n >= MAXIMUM_CAPACITY)
break;
else if (tab == table) {
int rs = resizeStamp(n);
if (sc < 0) {
Node<K,V>[] nt;
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
sc == rs + MAX_RESIZERS || (nt = nextTable) == null ||
transferIndex <= 0)
break;
if (U.compareAndSwapInt(this,null);
}
}
}
/**
* 这是ConcurrentHashMa的扩容<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>
* 将每<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin拷贝到新的table中
*/
private final void transfer(Node<K,V>[] nextTab) {
int n = tab.length,stride;
//如果可用<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a>数目>1,则stride=tab长度/<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a><a href="https://www.jb51.cc/tag/shuliang/" target="_blank">数量</a>
if ((stride = (N<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a> > 1) ? (n >>> 3) / N<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a> : n) < MIN_TRANSFER_STRIDE)
//如果此时stride<最小分割并行段数,则更新stride为最小分割并行段数
stride = MIN_TRANSFER_STRIDE; // subdivide range
//如果新table为null,则对新table初始化,长度为旧table的2倍
if (nextTab == null) { // initiating
try {
@SuppressWarnings("unchecked")
Node<K,?>[n << 1];//2倍扩容
nextTab = nt;
} catch (Throwable ex) { // try to <a href="https://www.jb51.cc/tag/cop/" target="_blank">cop</a>e with OOME
sizeCtl = Integer.MAX_VALUE;
return;
}
//nextTable指向新建table
nextTable = nextTab;
//转移索引改为n
transferIndex = n;
}
//新table长度
int nextn = nextTab.length;
//转移节点:设定为新table,hash值=-1,其他<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>为null
ForwardingNode<K,V> fwd = new ForwardingNode<K,V>(nextTab);
boolean advance = true;///并发扩容的关键<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a> 如果等于true 说明这个节点已经处理过
//确保在提交nextTab之前进行扫描
boolean finishing = false; // to ensure sweep before committing nextTab
for (int i = 0,bound = 0;;) {
Node<K,V> f; int fh;
////这个while循环体的作用就是在控制i-- 通过i--可以依次遍历原hash表中的节点
while (advance) {
int nextIndex,nextBound;
if (--i >= bound || finishing)
advance = false;
else if ((nextIndex = transferIndex) <= 0) {
i = -1;
advance = false;
}
else if (U.compareAndSwapInt
(this,TRANSFERINDEX,nextIndex,nextBound = (nextIndex > stride ?
nextIndex - stride : 0))) {
bound = nextBound;
i = nextIndex - 1;
advance = false;
}
}
if (i < 0 || i >= n || i + n >= nextn) {
int sc;
//如果所有的节点都已经完成复制工作 就把nextTable赋值给table 清空临时对象nextTabl
if (finishing) {
nextTable = null;
table = nextTab;
sizeCtl = (n << 1) - (n >>> 1);
return;
}
if (U.compareAndSwapInt(this,sc = sizeCtl,sc - 1)) {
if ((sc - 2) != resizeStamp(n) << RESIZE_STAMP_SHIFT)
return;
finishing = advance = true;
i = n; // recheck before commit
}
}
//i位置节点为null,原table中的i位置放入forwardNode节点，这个也是触发并发扩容的关键点；
else if ((f = tabAt(tab,i)) == null)
advance = casTabAt(tab,fwd);
//当前节点已经被复制过,直接跳过.是控制并发扩容的关键
else if ((fh = f.hash) == MOVED)
advance = true; // already processed
//同步代码块,复制节点,保证线程安全的复制,不重复不冲突
else {
synchronized (f) {
if (tabAt(tab,V> ln,hn;
//如果节点为链表节点
if (fh >= 0) {
int runBit = fh & n;
Node<K,V> lastRun = f;
//查找lastRun的位置
for (Node<K,V> p = f.next; p != null; p = p.next) {
int b = p.hash & n;
if (b != runBit) {
runBit = b;
lastRun = p;
}
}
if (runBit == 0) {
ln = lastRun;
hn = null;
}
else {
hn = lastRun;
ln = null;
}
//lastRun节点前的节点都会构造<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>反序链表,lastRun节点开始到后面的节点则顺序不变
for (Node<K,V> p = f; p != lastRun; p = p.next) {
int ph = p.hash; K pk = p.key; V pv = p.val;
if ((ph & n) == 0)
ln = new Node<K,V>(ph,pk,pv,ln);
else
hn = new Node<K,hn);
}
//在nextTable的i位置上插入<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>链表
setTabAt(nextTab,ln);
//在nextTable的i+n的位置上插入另<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>链表
setTabAt(nextTab,i + n,hn);
//在table的i位置上插入forwardNode节点 表示已经处理过该节点
setTabAt(tab,fwd);
//设置advance为true 返回到上面的while循环中 就可以执行i--操作
advance = true;
}
//如果被复制节点为红黑树节点包装类TreeBin,也做<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>反序处理，并且判断是否需要untreeify，
//把处理的结果分别放在nextTable的i和i+n的位置上
else if (f instanceof TreeBin) {
TreeBin<K,V> lo = null,loTail = null;
TreeNode<K,V> hi = null,hiTail = null;
int lc = 0,hc = 0;
for (Node<K,V> e = t.f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t; e != null; e = e.next) {
int h = e.hash;
TreeNode<K,V> p = new TreeNode<K,V>
(h,e.key,e.val,null);
if ((h & n) == 0) {
if ((p.prev = loTail) == null)
lo = p;
else
loTail.next = p;
loTail = p;
++lc;
}
else {
if ((p.prev = hiTail) == null)
hi = p;
else
hiTail.next = p;
hiTail = p;
++hc;
}
}
////如果扩容后已经不再需要tree的结构 反向转换为链表结构
ln = (lc <= UNTREEIFY_THRESHOLD) ? untreeify(lo) :
(hc != 0) ? new TreeBin<K,V>(lo) : t;
hn = (hc <= UNTREEIFY_THRESHOLD) ? untreeify(hi) :
(lc != 0) ? new TreeBin<K,V>(hi) : t;
//下面<a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>和链表处理一致
setTabAt(nextTab,ln);
setTabAt(nextTab,hn);
setTabAt(tab,fwd);
advance = true;
}
}
}
}
}
}
/* ---------------- Counter support 计数器<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a><a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>-------------- */
/**
* A padded cell for <a href="https://www.jb51.cc/tag/dis/" target="_blank">dis</a>tributing counts. Adapted from LongAdder
* and Striped64. See their internal docs for explanation.
* 用于分发计数的填充单元格。改编自LongAdder和Striped64。请参阅他们的内部文档以获得解释。
* 用于辅助sumCount()<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>
*/
@sun.misc.Contended static final class CounterCell {
//内存可见value
volatile long value;
CounterCell(long x) { value = x; }
}
//ConcurrentHashMap中节点总数
final long sumCount() {
CounterCell[] as = counterCells; CounterCell a;
long sum = baseCount;
if (as != null) {
for (int i = 0; i < as.length; ++i) {
if ((a = as[i]) != null)
sum += a.value;
}
}
return sum;
}
/**
* LongAdder是java8新增的.
* LongAdders与ConcurrentHashMap一起使用，以维护可伸缩的频率映射（一种直方图或多重集）。
* 例如，要为ConcurrentHashMap<String，LongAdder> freqs <a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a><a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>计数，
* 初始化（如果尚未存在），可以使用freqs.co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>teIfAbsent（k - > new LongAdder（））
*/
private final void fullAddCount(long x,boolean wasUncontended) {
int h;
if ((h = ThreadLocalRandom.getProbe()) == 0) {
ThreadLocalRandom.localInit(); // force initialization
h = ThreadLocalRandom.getProbe();
wasUncontended = true;
}
boolean collide = false; // True if last slot nonempty
for (;;) {
CounterCell[] as; CounterCell a; int n; long v;
if ((as = counterCells) != null && (n = as.length) > 0) {
if ((a = as[(n - 1) & h]) == null) {
if (cellsBusy == 0) { // Try to attach new Cell
CounterCell r = new CounterCell(x); // Optimistic create
if (cellsBusy == 0 &&
U.compareAndSwapInt(this,CELLSBUSY,1)) {
boolean created = false;
try { // Recheck under lock
CounterCell[] rs; int m,j;
if ((rs = counterCells) != null &&
(m = rs.length) > 0 &&
rs[j = (m - 1) & h] == null) {
rs[j] = r;
created = true;
}
} finally {
cellsBusy = 0;
}
if (created)
break;
continue; // Slot is <a href="https://www.jb51.cc/tag/Now/" target="_blank">Now</a> non-empty
}
}
collide = false;
}
else if (!wasUncontended) // CAS already k<a href="https://www.jb51.cc/tag/Now/" target="_blank">Now</a>n to fail
wasUncontended = true; // Continue after rehash
else if (U.compareAndSwapLong(a,v + x))
break;
else if (counterCells != as || n >= N<a href="https://www.jb51.cc/tag/cpu/" target="_blank">cpu</a>)
collide = false; // At max size or stale
else if (!collide)
collide = true;
else if (cellsBusy == 0 &&
U.compareAndSwapInt(this,1)) {
try {
if (counterCells == as) {// Expand table unless stale
CounterCell[] rs = new CounterCell[n << 1];
for (int i = 0; i < n; ++i)
rs[i] = as[i];
counterCells = rs;
}
} finally {
cellsBusy = 0;
}
collide = false;
continue; // Retry with expanded table
}
h = ThreadLocalRandom.advanceProbe(h);
}
else if (cellsBusy == 0 && counterCells == as &&
U.compareAndSwapInt(this,1)) {
boolean init = false;
try { // Initialize table
if (counterCells == as) {
CounterCell[] rs = new CounterCell[2];
rs[h & 1] = new CounterCell(x);
counterCells = rs;
init = true;
}
} finally {
cellsBusy = 0;
}
if (init)
break;
}
else if (U.compareAndSwapLong(this,v = baseCount,v + x))
break; // Fall back on using base
}
}
/* ---------------- TreeBins 转换相关-------------- */
//在指定索引处替换掉所有的链表节点为红黑树节点;当然如果此时table特别小,则不执行转换操作,而应执行resize操作.
private final void treeifyBin(Node<K,int index) {
Node<K,V> b; int n,sc;
if (tab != null) {
if ((n = tab.length) < MIN_TREEIFY_CAPACITY)
tryPresize(n << 1);
else if ((b = tabAt(tab,index)) != null && b.hash >= 0) {
synchronized (b) {
if (tabAt(tab,index) == b) {
TreeNode<K,tl = null;
for (Node<K,V> e = b; e != null; e = e.next) {
TreeNode<K,V> p =
new TreeNode<K,V>(e.hash,null);
if ((p.prev = tl) == null)
hd = p;
else
tl.next = p;
tl = p;
}
//TreeBin封装了TreeNode节点,将索引index处节点设置为新的TreeBin节点
setTabAt(tab,index,V>(hd));
}
}
}
}
}
//将给定list中红黑树节点全部替换为链表节点,并返回链表
static <K,V> untreeify(Node<K,V> b) {
Node<K,tl = null;
for (Node<K,V> q = b; q != null; q = q.next) {
Node<K,V> p = new Node<K,V>(q.hash,null);
if (tl == null)
hd = p;
else
tl.next = p;
tl = p;
}
return hd;
}
/* ---------------- TreeNodes -------------- */
/**
* Nodes for use in TreeBins
* 也是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>核心的数据结构.
* 当链表长度过长的时候，会转换为TreeNode。但是与HashMap不相同的是，它并不是直接转换为红黑树，
* 而是把这些结点包装成TreeNode放在TreeBin对象中，由TreeBin完成对红黑树的包装。
* 而且TreeNode在ConcurrentHashMap集成自Node类，而并非HashMap中的集成自LinkedHashMap.Entry<K,V>类，
* 也就是说TreeNode带有next指针，这样做的目的是方便基于TreeBin的访问。
*/
static final class TreeNode<K,V> {
//用于红黑树节点连接,因为本身是<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>链表,所以需要<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>指针指向双亲节点
TreeNode<K,V> parent; // red-black tree links
TreeNode<K,V> left;
TreeNode<K,V> right;
//前驱节点指针,用于<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>节点
TreeNode<K,V> prev; // needed to unlink next upon deletion
boolean red;
TreeNode(int hash,V> next,TreeNode<K,V> parent) {
super(hash,next);
this.parent = parent;
}
Node<K,Object k) {
return findTreeNode(h,null);
}
/**
* 从给定根节点出发,查找指定key的树节点.
* 红黑树节点排序规则:按照节点的hash值排序
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m h 查找节点hash值
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m k 查找节点key
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m kc
*
*/
final TreeNode<K,V> findTreeNode(int h,Class<?> kc) {
//指定key不为null
if (k != null) {
TreeNode<K,V> p = this;
do {
int ph,dir; K pk; TreeNode<K,V> q;
TreeNode<K,V> pl = p.left,pr = p.right;
//查找节点hash值比当前节点p的hash值小,则转向p的左孩子进行遍历,可见 红黑树按照节点的hash值排序
if ((ph = p.hash) > h)
p = pl;
//转右孩子
else if (ph < h)
p = pr;
//查找节点和当前p节点hash值和key都一样,则查找成功,返回查找节点
else if ((pk = p.key) == k || (pk != null && k.equals(pk)))
return p;
else if (pl == null)
p = pr;
else if (pr == null)
p = pl;
else if ((kc != null ||
(kc = comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bleClassFor(k)) != null) &&
(dir = compareComp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bles(kc,pk)) != 0)
p = (dir < 0) ? pl : pr;
//递归查找
else if ((q = pr.findTreeNode(h,kc)) != null)
return q;
else
p = pl;
} while (p != null);
}
return null;
}
}
/* ---------------- TreeBins -------------- */
/**
* TreeNodes用作bin的头节点.在实际的ConcurrentHashMap“数组”中，存放的是TreeBin对象，而不是TreeNode对象，这是与HashMap的区别。
* TreeBins不保存key和value,而是指向TreeNodes链表及其根节点.
* TreeBin还维持<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>读写锁,从而保证在红黑树重构前,优先完成读操作,然后再执行写操作.
*/
static final class TreeBin<K,V> {
//<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>TreeBin既要有指向根节点的指针,也要有指向第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点指针
TreeNode<K,V> root;//根节点
volatile TreeNode<K,V> f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;//第<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>节点
volatile Thread waiter;//等待线程
volatile int lockState;//锁状态
//lockState的一些值
static final int WRITER = 1; // 持有写锁的锁状态值
static final int WAITER = 2; // 等待写锁的锁状态值
static final int READER = 4; // 设置读锁时的锁状态增量值
/**
* 插入节点时,如果hash值相同而又没有其它可比较的元素时,此<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>可用于打破此种插入僵局.
* 我们不需要<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>全局有序,只需要<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>插入规则,保证在调整平衡时可以维持等价关系.
* 僵局关系的进一步打破也使得测试变得简单了一些.
* 和hashmap<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>一样
*/
static int tieBreakOrder(Object a,Object b) {
int d;
//如果a为null,或者b为null,或者a和b是同<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>类的实
if (a == null || b == null ||
(d = a.getClass().getName().
compar<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>(b.getClass().getName())) == 0)//反射<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>类名
//identityHashCode():无论给定对象的类是否覆盖hashCode(),都会返回给定对象的哈希码,与<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>hashCode()返回的哈希码相同。
//如果传入参数a为null,则返回值为0;
d = (Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank">stem</a>.identityHashCode(a) <= Sy<a href="https://www.jb51.cc/tag/stem/" target="_blank">stem</a>.identityHashCode(b) ?
-1 : 1);
return d;
}
//利用头节点为b的初始set节点集合,创建<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>bin,里面放了一棵红黑树
TreeBin(TreeNode<K,V> b) {
//这就它的构造<a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>,TREEBIN=-1,树根节点的hash值
super(TREEBIN,null);
this.f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t = b;
TreeNode<K,V> r = null;
for (TreeNode<K,V> x = b,next; x != null; x = next) {
next = (TreeNode<K,V>)x.next;
x.left = x.right = null;
if (r == null) {
x.parent = null;
x.red = false;
r = x;
}
else {
K k = x.key;
int h = x.hash;
Class<?> kc = null;
for (TreeNode<K,V> p = r;;) {
int dir,ph;
K pk = p.key;
if ((ph = p.hash) > h)
dir = -1;
else if (ph < h)
dir = 1;
else if ((kc == null &&
(kc = comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bleClassFor(k)) == null) ||
(dir = compareComp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bles(kc,pk)) == 0)
dir = tieBreakOrder(k,pk);
TreeNode<K,V> xp = p;
if ((p = (dir <= 0) ? p.left : p.right) == null) {
x.parent = xp;
if (dir <= 0)
xp.left = x;
else
xp.right = x;
r = balanceInsertion(r,x);
break;
}
}
}
}
this.root = r;
assert checkInvariants(root);
}
//红黑树重构开始前,<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>写锁
private final void lockRoot() {
if (!U.compareAndSwapInt(this,LOCKSTATE,WRITER))
contendedLock(); // offload to sep<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>te method
}
//红黑树重构完成后,释放写锁
private final void unlockRoot() {
lockState = 0;
}
//root被锁定时,阻塞其他请求.
private final void contendedLock() {
boolean waiting = false;
for (int s;;) {
if (((s = lockState) & ~WAITER) == 0) {
if (U.compareAndSwapInt(this,s,WRITER)) {
if (waiting)
waiter = null;
return;
}
}
else if ((s & WAITER) == 0) {
if (U.compareAndSwapInt(this,s | WAITER)) {
waiting = true;
waiter = Thread.currentThread();
}
}
else if (waiting)
LockSupport.park(this);
}
}
//根据给定hash值和key查找树节点.
//首先尝试从树根节点开始查找
//如果<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>不到bin的锁,则<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a>需要线性时间:o(n),也就是从头到位底链表进行了遍历
//所以TreeBin的查找节点过程:时间复杂度为o(logN)或为o(N)
final Node<K,Object k) {
if (k != null) {
for (Node<K,V> e = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t; e != null; ) {
int s; K ek;
if (((s = lockState) & (WAITER|WRITER)) != 0) {
if (e.hash == h &&
((ek = e.key) == k || (ek != null && k.equals(ek))))
return e;
e = e.next;
}
else if (U.compareAndSwapInt(this,s + READER)) {
TreeNode<K,p;
try {
p = ((r = root) == null ? null :
r.findTreeNode(h,null));
} finally {
Thread w;
if (U.getAndAddInt(this,-READER) ==
(READER|WAITER) && (w = waiter) != null)
LockSupport.unpark(w);
}
return p;
}
}
}
return null;
}
//<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a><a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>树节点
final TreeNode<K,V> putTreeVal(int h,K k,V v) {
Class<?> kc = null;
boolean searched = false;
for (TreeNode<K,V> p = root;;) {
int dir,ph; K pk;
if (p == null) {
f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t = root = new TreeNode<K,null);
break;
}
else if ((ph = p.hash) > h)
dir = -1;
else if (ph < h)
dir = 1;
else if ((pk = p.key) == k || (pk != null && k.equals(pk)))
return p;
else if ((kc == null &&
(kc = comp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bleClassFor(k)) == null) ||
(dir = compareComp<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>bles(kc,pk)) == 0) {
if (!searched) {
TreeNode<K,V> q,ch;
searched = true;
if (((ch = p.left) != null &&
(q = ch.findTreeNode(h,kc)) != null) ||
((ch = p.right) != null &&
(q = ch.findTreeNode(h,kc)) != null))
return q;
}
dir = tieBreakOrder(k,pk);
}
TreeNode<K,V> xp = p;
if ((p = (dir <= 0) ? p.left : p.right) == null) {
TreeNode<K,V> x,f = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t = x = new TreeNode<K,xp);
if (f != null)
f.prev = x;
if (dir <= 0)
xp.left = x;
else
xp.right = x;
if (!xp.red)
x.red = true;
else {
lockRoot();
try {
root = balanceInsertion(root,x);
} finally {
unlockRoot();
}
}
break;
}
}
assert checkInvariants(root);
return null;
}
/**
* 移除<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>树节点.在此<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>被<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>前此节点必须存在.
* 这比典型的红黑<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a><a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>更混乱，因为我们不能交换内部节点和其后继叶子节点的<a href="https://www.jb51.cc/tag/neirong/" target="_blank">内容</a>。
* 所以,取而代之的是交换树<a href="https://www.jb51.cc/tag/lianjie/" target="_blank">链接</a>。
* @return 返回值为true,代表<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>节点后,bin内节点太少,需要将红黑树转为链表.
*/
final boolean removeTreeNode(TreeNode<K,V> p) {
TreeNode<K,V> next = (TreeNode<K,V>)p.next;
TreeNode<K,V> pred = p.prev; // unlink traversal pointers
TreeNode<K,rl;
if (pred == null)
f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t = next;
else
pred.next = next;
if (next != null)
next.prev = pred;
if (f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t == null) {
root = null;
return true;
}
if ((r = root) == null || r.right == null || // too small
(rl = r.left) == null || rl.left == null)
return true;
lockRoot();
try {
TreeNode<K,V> replacement;
TreeNode<K,V> pl = p.left;
TreeNode<K,V> pr = p.right;
if (pl != null && pr != null) {
TreeNode<K,V> s = pr,sl;
while ((sl = s.left) != null) // find successor
s = sl;
boolean c = s.red; s.red = p.red; p.red = c; // swap colors
TreeNode<K,V> sr = s.right;
TreeNode<K,V> pp = p.parent;
if (s == pr) { // p was s's direct parent
p.parent = s;
s.right = p;
}
else {
TreeNode<K,V> sp = s.parent;
if ((p.parent = sp) != null) {
if (s == sp.left)
sp.left = p;
else
sp.right = p;
}
if ((s.right = pr) != null)
pr.parent = s;
}
p.left = null;
if ((p.right = sr) != null)
sr.parent = p;
if ((s.left = pl) != null)
pl.parent = s;
if ((s.parent = pp) == null)
r = s;
else if (p == pp.left)
pp.left = s;
else
pp.right = s;
if (sr != null)
replacement = sr;
else
replacement = p;
}
else if (pl != null)
replacement = pl;
else if (pr != null)
replacement = pr;
else
replacement = p;
if (replacement != p) {
TreeNode<K,V> pp = replacement.parent = p.parent;
if (pp == null)
r = replacement;
else if (p == pp.left)
pp.left = replacement;
else
pp.right = replacement;
p.left = p.right = p.parent = null;
}
root = (p.red) ? r : balanceDeletion(r,replacement);
if (p == replacement) { // detach pointers
TreeNode<K,V> pp;
if ((pp = p.parent) != null) {
if (p == pp.left)
pp.left = null;
else if (p == pp.right)
pp.right = null;
p.parent = null;
}
}
} finally {
unlockRoot();
}
assert checkInvariants(root);
return false;
}
/* --------------------红黑树<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>,全部改自CLR算法---------------------------------------- */
//左旋
static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root,pp,rl;
if (p != null && (r = p.right) != null) {
if ((rl = p.right = r.left) != null)
rl.parent = p;
if ((pp = r.parent = p.parent) == null)
(root = r).red = false;
else if (pp.left == p)
pp.left = r;
else
pp.right = r;
r.left = p;
p.parent = r;
}
return root;
}
//右旋
static <K,V> rotateRight(TreeNode<K,V> l,lr;
if (p != null && (l = p.left) != null) {
if ((lr = p.left = l.right) != null)
lr.parent = p;
if ((pp = l.parent = p.parent) == null)
(root = l).red = false;
else if (pp.right == p)
pp.right = l;
else
pp.left = l;
l.right = p;
p.parent = l;
}
return root;
}
//插入后,调整平衡和颜色
static <K,V> balanceInsertion(TreeNode<K,V> x) {
x.red = true;
for (TreeNode<K,V> xp,xpp,xppl,xppr;;) {
if ((xp = x.parent) == null) {
x.red = false;
return x;
}
else if (!xp.red || (xpp = xp.parent) == null)
return root;
if (xp == (xppl = xpp.left)) {
if ((xppr = xpp.right) != null && xppr.red) {
xppr.red = false;
xp.red = false;
xpp.red = true;
x = xpp;
}
else {
if (x == xp.right) {
root = rotateLeft(root,x = xp);
xpp = (xp = x.parent) == null ? null : xp.parent;
}
if (xp != null) {
xp.red = false;
if (xpp != null) {
xpp.red = true;
root = rotateRight(root,xpp);
}
}
}
}
else {
if (xppl != null && xppl.red) {
xppl.red = false;
xp.red = false;
xpp.red = true;
x = xpp;
}
else {
if (x == xp.left) {
root = rotateRight(root,x = xp);
xpp = (xp = x.parent) == null ? null : xp.parent;
}
if (xp != null) {
xp.red = false;
if (xpp != null) {
xpp.red = true;
root = rotateLeft(root,xpp);
}
}
}
}
}
}
//<a href="https://www.jb51.cc/tag/shanchu/" target="_blank">删除</a>后调整平衡和颜色
static <K,V> balanceDeletion(TreeNode<K,V> x) {
for (TreeNode<K,xpl,xpr;;) {
if (x == null || x == root)
return root;
else if ((xp = x.parent) == null) {
x.red = false;
return x;
}
else if (x.red) {
x.red = false;
return root;
}
else if ((xpl = xp.left) == x) {
if ((xpr = xp.right) != null && xpr.red) {
xpr.red = false;
xp.red = true;
root = rotateLeft(root,xp);
xpr = (xp = x.parent) == null ? null : xp.right;
}
if (xpr == null)
x = xp;
else {
TreeNode<K,V> sl = xpr.left,sr = xpr.right;
if ((sr == null || !sr.red) &&
(sl == null || !sl.red)) {
xpr.red = true;
x = xp;
}
else {
if (sr == null || !sr.red) {
if (sl != null)
sl.red = false;
xpr.red = true;
root = rotateRight(root,xpr);
xpr = (xp = x.parent) == null ?
null : xp.right;
}
if (xpr != null) {
xpr.red = (xp == null) ? false : xp.red;
if ((sr = xpr.right) != null)
sr.red = false;
}
if (xp != null) {
xp.red = false;
root = rotateLeft(root,xp);
}
x = root;
}
}
}
else { // symmetric
if (xpl != null && xpl.red) {
xpl.red = false;
xp.red = true;
root = rotateRight(root,xp);
xpl = (xp = x.parent) == null ? null : xp.left;
}
if (xpl == null)
x = xp;
else {
TreeNode<K,V> sl = xpl.left,sr = xpl.right;
if ((sl == null || !sl.red) &&
(sr == null || !sr.red)) {
xpl.red = true;
x = xp;
}
else {
if (sl == null || !sl.red) {
if (sr != null)
sr.red = false;
xpl.red = true;
root = rotateLeft(root,xpl);
xpl = (xp = x.parent) == null ?
null : xp.left;
}
if (xpl != null) {
xpl.red = (xp == null) ? false : xp.red;
if ((sl = xpl.left) != null)
sl.red = false;
}
if (xp != null) {
xp.red = false;
root = rotateRight(root,xp);
}
x = root;
}
}
}
}
}
//递归不变检查,用于检查整个红黑树连接上是否有<a href="https://www.jb51.cc/tag/cuowu/" target="_blank">错误</a>
static <K,V> boolean checkInvariants(TreeNode<K,V> t) {
//tp双亲,tl左孩子,tr右孩子,tb前驱,tn后继
TreeNode<K,V> tp = t.parent,tl = t.left,tr = t.right,tb = t.prev,tn = (TreeNode<K,V>)t.next;
//双亲不为null,前驱的后继不是当前节点t,故连接<a href="https://www.jb51.cc/tag/cuowu/" target="_blank">错误</a>,返回false
if (tb != null && tb.next != t)
return false;
//后继不为null,后继的前驱不为当前节点t,故<a href="https://www.jb51.cc/tag/lianjie/" target="_blank">链接</a><a href="https://www.jb51.cc/tag/cuowu/" target="_blank">错误</a>,返回false
if (tn != null && tn.prev != t)
return false;
if (tp != null && t != tp.left && t != tp.right)
return false;
if (tl != null && (tl.parent != t || tl.hash > t.hash))
return false;
if (tr != null && (tr.parent != t || tr.hash < t.hash))
return false;
if (t.red && tl != null && tl.red && tr != null && tr.red)
return false;
if (tl != null && !checkInvariants(tl))
return false;
if (tr != null && !checkInvariants(tr))
return false;
return true;
}
private static final sun.misc.Unsafe U;
private static final long LOCKSTATE;
static {
try {
U = sun.misc.Unsafe.getUnsafe();
Class<?> k = TreeBin.class;
LOCKSTATE = U.objectFieldOffset
(k.getDeclaredField("lockState"));//反射<a href="https://www.jb51.cc/tag/huoquziduan/" target="_blank">获取字段</a>值
} catch (Exception e) {
throw new Error(e);
}
}
}
/* ----------------Table 遍历 -------------- */
//在继续使用当前table前,必须记录转发表的区域的表，其长度和当前遍历索引。
static final class TableStack<K,V> {
int length;
int index;
Node<K,V>[] tab;
TableStack<K,V> next;
}
/**
* 对诸如containsValue之类的<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>要进行封装遍历.alsoserves是其他迭代器和分割器的基类.
* 遍历过程中,可能出现resize,为了面对可能的持续调整,需要记录大量的状态,因此很难通过volatile进行优化,* 即便如此，遍历仍然保持合理的吞吐量。通常情况下，迭代逐个进行遍历列表。但是，如果表已经调整大小，那么所有未来的步骤
* 必须遍历当前索引处的bin以及（index + baseSize）.
* 为了处理<a href="https://www.jb51.cc/tag/yonghu/" target="_blank">用户</a>间跨线程共享迭代器之<a href="https://www.jb51.cc/tag/jiande/" target="_blank">间的</a>冲突,如果迭代器索引边界失效,则迭代停止.
*/
static class Traverser<K,V> {
Node<K,V>[] tab; // current table; updated if resized
Node<K,V> next; // the next entry to use
TableStack<K,V> stack,spare; // to save/restore on ForwardingNodes
int index; // index of bin to use next
int baseIndex; // current index of initial table
int baseLimit; // index bound for initial table
final int baseSize; // initial table size
Traverser(Node<K,int size,int index,int limit) {
this.tab = tab;
this.baseSize = size;
this.baseIndex = this.index = index;
this.baseLimit = limit;
this.next = null;
}
//继续遍历,返回下<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>有效节点,如果没有则返回null
final Node<K,V> advance() {
Node<K,V> e;
if ((e = next) != null)
e = e.next;
for (;;) {
Node<K,V>[] t; int i,n; // must use locals in checks
if (e != null)
return next = e;
if (baseIndex >= baseLimit || (t = tab) == null ||
(n = t.length) <= (i = index) || i < 0)
return next = null;
if ((e = tabAt(t,i)) != null && e.hash < 0) {
if (e instanceof ForwardingNode) {
tab = ((ForwardingNode<K,V>)e).nextTable;
e = null;
pushState(t,n);
continue;
}
else if (e instanceof TreeBin)
e = ((TreeBin<K,V>)e).f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
else
e = null;
}
if (stack != null)
recoverState(n);
else if ((index = i + baseSize) >= n)
index = ++baseIndex; // visit upper slots if present
}
}
//遇到转发节点时,保存遍历状态
private void pushState(Node<K,V>[] t,int n) {
TableStack<K,V> s = spare; // reuse if possible
if (s != null)
spare = s.next;
else
s = new TableStack<K,V>();
s.tab = t;
s.length = n;
s.index = i;
s.next = stack;
stack = s;
}
//取出遍历状态栈的栈定元素.
private void recoverState(int n) {
TableStack<K,V> s; int len;
while ((s = stack) != null && (index += (len = s.length)) >= n) {
n = len;
index = s.index;
tab = s.tab;
s.tab = null;
TableStack<K,V> next = s.next;
s.next = spare; // save for reuse
stack = next;
spare = s;
}
if (s == null && (index += baseSize) >= n)
index = ++baseIndex;
}
}
//基于key,entry的迭代器.在Traverser基础上<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>了一些变量以<a href="https://www.jb51.cc/tag/zhichi/" target="_blank">支持</a>i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.remove<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>
static class BaseI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V> extends Traverser<K,V> {
final ConcurrentHashMap<K,V> map;
Node<K,V> lastReturned;
BaseI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,int limit,ConcurrentHashMap<K,V> map) {
super(tab,size,limit);
this.map = map;
advance();
}
public final boolean hasNext() { return next != null; }
public final boolean hasMoreElements() { return next != null; }
public final void remove() {
Node<K,V> p;
if ((p = lastReturned) == null)
throw new Ille<a href="https://www.jb51.cc/tag/gal/" target="_blank">gal</a>StateException();
lastReturned = null;
map.replaceNode(p.key,null);
}
}
//key迭代器
static final class KeyI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V> extends BaseI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K>,Enumeration<K> {
KeyI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,limit,map);
}
public final K next() {
Node<K,V> p;
if ((p = next) == null)
throw new NoSuchElementException();
K k = p.key;
lastReturned = p;
advance();
return k;
}
public final K nextElement() { return next(); }
}
//value迭代器
static final class ValueI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V>,Enumeration<V> {
ValueI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,map);
}
public final V next() {
Node<K,V> p;
if ((p = next) == null)
throw new NoSuchElementException();
V v = p.val;
lastReturned = p;
advance();
return v;
}
public final V nextElement() { return next(); }
}
//Entry迭代器
static final class EntryI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<Map.Entry<K,V>> {
EntryI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,map);
}
public final Map.Entry<K,V> next() {
Node<K,V> p;
if ((p = next) == null)
throw new NoSuchElementException();
K k = p.key;
V v = p.val;
lastReturned = p;
advance();
return new MapEntry<K,V>(k,map);
}
}
//从EntryI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor导出<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>Entry
static final class MapEntry<K,V> {
final K key; // non-null
V val; // non-null
final ConcurrentHashMap<K,V> map;
MapEntry(K key,V> map) {
this.key = key;
this.val = val;
this.map = map;
}
public K getKey() { return key; }
public V getValue() { return val; }
public int hashCode() { return key.hashCode() ^ val.hashCode(); }
public String toString() { return key + "=" + val; }
public boolean equals(Object o) {
Object k,v; Map.Entry<?,?>)o).getKey()) != null &&
(v = e.getValue()) != null &&
(k == key || k.equals(key)) &&
(v == val || v.equals(val)));
}
/**
* 设置我们的entry的value并写入map。
* 注意:返回的值<a href="https://www.jb51.cc/tag/zaizheli/" target="_blank">在这里</a>有点随便。因为可能返回的值已经被其它线程做过更改了,而返回值并未<a href="https://www.jb51.cc/tag/huoqu/" target="_blank">获取</a>到最新的值.
*/
public V setValue(V value) {
if (value == null) throw new NullPointerException();
V v = val;
val = value;
map.put(key,value);
return v;
}
}
//key分割器
static final class KeySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K> {
long est; // size estimate
KeySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,long est) {
super(tab,limit);
this.est = est;
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K> trySplit() {
int i,h;
return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
new KeySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>(tab,baseSize,baseLimit = h,est >>>= 1);
}
public void forEachRemaining(Consumer<? super K> action) {
if (action == null) throw new NullPointerException();
for (Node<K,V> p; (p = advance()) != null;)
action.accept(p.key);
}
public boolean tryAdvance(Consumer<? super K> action) {
if (action == null) throw new NullPointerException();
Node<K,V> p;
if ((p = advance()) == null)
return false;
action.accept(p.key);
return true;
}
public long estimateSize() { return est; }
public int <a href="https://www.jb51.cc/tag/characteristics/" target="_blank">characteristics</a>() {
return Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.<a href="https://www.jb51.cc/tag/dis/" target="_blank">dis</a>TINCT | Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.CONCURRENT |
Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.NONNULL;
}
}
//value分割器
static final class ValueSpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V> {
long est; // size estimate
ValueSpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,limit);
this.est = est;
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V> trySplit() {
int i,h;
return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
new ValueSpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,est >>>= 1);
}
public void forEachRemaining(Consumer<? super V> action) {
if (action == null) throw new NullPointerException();
for (Node<K,V> p; (p = advance()) != null;)
action.accept(p.val);
}
public boolean tryAdvance(Consumer<? super V> action) {
if (action == null) throw new NullPointerException();
Node<K,V> p;
if ((p = advance()) == null)
return false;
action.accept(p.val);
return true;
}
public long estimateSize() { return est; }
public int <a href="https://www.jb51.cc/tag/characteristics/" target="_blank">characteristics</a>() {
return Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.CONCURRENT | Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.NONNULL;
}
}
//entry分割器
static final class EntrySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,V>
implements Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<Map.Entry<K,V>> {
final ConcurrentHashMap<K,V> map; // To export MapEntry
long est; // size estimate
EntrySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(Node<K,long est,limit);
this.map = map;
this.est = est;
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<Map.Entry<K,V>> trySplit() {
int i,h;
return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
new EntrySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,est >>>= 1,map);
}
public void forEachRemaining(Consumer<? super Map.Entry<K,V>> action) {
if (action == null) throw new NullPointerException();
for (Node<K,V> p; (p = advance()) != null; )
action.accept(new MapEntry<K,V>(p.key,p.val,map));
}
public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
if (action == null) throw new NullPointerException();
Node<K,V> p;
if ((p = advance()) == null)
return false;
action.accept(new MapEntry<K,map));
return true;
}
public long estimateSize() { return est; }
public int <a href="https://www.jb51.cc/tag/characteristics/" target="_blank">characteristics</a>() {
return Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.<a href="https://www.jb51.cc/tag/dis/" target="_blank">dis</a>TINCT | Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.CONCURRENT |
Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor.NONNULL;
}
}
/*---------并行批量操作 P<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llel bulk operations---------*/
/**
* 计算批量任务的初始批次值。
* 在执行最终的操作之前,返回值将是将任务一分为二的<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>指数值exp2.我的理解是,如果返回为3,则是将任务分为8部分,并行处理.
* 此值计算速度很快，适合用作二划分
*/
final int batchFor(long b) {
long n;
if (b == Long.MAX_VALUE || (n = sumCount()) <= 1L || n < b)
return 0;
int sp = ForkJoinPool.getCommonPoolP<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelism() << 2; // slack of 4
return (b <= 0L || (n /= b) >= sp) ? sp : (int)n;
}
//@since 1.8
public void forEach(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,BiConsumer<? super K,? super V> action) {
if (action == null) throw new NullPointerException();
new ForEachMappingTask<K,V>
(null,batchFor(p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold),table,action).invoke();
}
//@since 1.8
public <U> void forEach(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> transformer,Consumer<? super U> action) {
if (transformer == null || action == null)
throw new NullPointerException();
new ForEachTransformedMappingTask<K,V,U>
(null,transformer,action).invoke();
}
/**
* 对每个(key,value)应用给定的<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a><a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>并返回<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>非空结果，如果没有，则返回null。
* 成功后，进一步的元素处理将被抑制，<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a><a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>的任何其他并行<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>的结果都将被忽略。
* @since 1.8
*/
public <U> U search(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> searchFunction) {
if (searchFunction == null) throw new NullPointerException();
return new SearchMappingsTask<K,searchFunction,new <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U>()).invoke();
}
//since 1.8,合并结果值
public <U> U reduce(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,BiFunction<? super U,? super U,? extends U> reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceMappingsTask<K,reducer).invoke();
}
/**
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m basis reduction操作的<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认初始化值
* @since 1.8
*/
public double reduc<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>Double(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleBiFunction<? super K,? super V> transformer,double basis,DoubleBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,basis,reducer).invoke();
}
//@since 1.8
public long reduc<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>Long(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToLongBiFunction<? super K,long basis,LongBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceMappingsToLongTask<K,reducer).invoke();
}
// @since 1.8
public int reduc<a href="https://www.jb51.cc/tag/eto/" target="_blank">eto</a>Int(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToIntBiFunction<? super K,int basis,IntBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceMappingsToIntTask<K,reducer).invoke();
}
/**
* Performs the given action for each key.
* @since 1.8
*/
public void forEachKey(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Consumer<? super K> action) {
if (action == null) throw new NullPointerException();
new ForEachKeyTask<K,action).invoke();
}
/**
* @since 1.8
*/
public <U> void forEachKey(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Consumer<? super U> action) {
if (transformer == null || action == null)
throw new NullPointerException();
new ForEachTransformedKeyTask<K,action).invoke();
}
/**
* 根据给定<a href="https://www.jb51.cc/tag/chaxun/" target="_blank">查询</a><a href="https://www.jb51.cc/tag/hanshu/" target="_blank">函数</a>,返回<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>非null结果.如果没有则返回null
* 成功后，进一步的元素处理将被抑制，<a href="https://www.jb51.cc/tag/sousuo/" target="_blank">搜索</a><a href="https://www.jb51.cc/tag/gongneng/" target="_blank">功能</a>的任何其他并行<a href="https://www.jb51.cc/tag/diaoyong/" target="_blank">调用</a>的结果都将被忽略。
* @since 1.8
*/
public <U> U searchKeys(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> searchFunction) {
if (searchFunction == null) throw new NullPointerException();
return new SearchKeysTask<K,new <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U>()).invoke();
}
/**
* 所有key的<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>合并操作
* @since 1.8
*/
public K reduceKeys(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? super K,? extends K> reducer) {
if (reducer == null) throw new NullPointerException();
return new ReduceKeysTask<K,reducer).invoke();
}
/**
* 对key的reduce操作
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold 并行被处理的元素的个数阈值
* @since 1.8
*/
public <U> U reduceKeys(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceKeysTask<K,reducer).invoke();
}
/**
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m basis reduction操作的初始化值
* @since 1.8
*/
public double reduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>uble(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super K> transformer,DoubleBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public long reduceKeysToLong(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToLongFunction<? super K> transformer,LongBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceKeysToLongTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public int reduceKeysToInt(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToIntFunction<? super K> transformer,IntBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceKeysToIntTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public void forEachValue(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Consumer<? super V> action) {
if (action == null)
throw new NullPointerException();
new ForEachValueTask<K,action).invoke();
}
/**
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold 并行被处理的元素的个数阈值
* @since 1.8
*/
public <U> void forEachValue(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Function<? super V,Consumer<? super U> action) {
if (transformer == null || action == null)
throw new NullPointerException();
new ForEachTransformedValueTask<K,action).invoke();
}
/**
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold 并行被处理的元素的个数阈值
* @since 1.8
*/
public <U> U searchValues(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> searchFunction) {
if (searchFunction == null) throw new NullPointerException();
return new SearchValuesTask<K,new <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U>()).invoke();
}
/**
*
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold t并行被处理的元素的个数阈值
* @since 1.8
*/
public V reduceValues(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends V> reducer) {
if (reducer == null) throw new NullPointerException();
return new ReduceValuesTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public <U> U reduceValues(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceValuesTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public double reduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>uble(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super V> transformer,DoubleBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public long reduceValuesToLong(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToLongFunction<? super V> transformer,LongBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceValuesToLongTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public int reduceValuesToInt(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToIntFunction<? super V> transformer,IntBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceValuesToIntTask<K,reducer).invoke();
}
/**
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold 并行被处理的元素的个数阈值
* @since 1.8
*/
public void forEachEntry(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Consumer<? super Map.Entry<K,V>> action) {
if (action == null) throw new NullPointerException();
new ForEachEntryTask<K,V>(null,action).invoke();
}
/**
* @since 1.8
*/
public <U> void forEachEntry(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,Function<Map.Entry<K,Consumer<? super U> action) {
if (transformer == null || action == null)
throw new NullPointerException();
new ForEachTransformedEntryTask<K,action).invoke();
}
/**
* @since 1.8
*/
public <U> U searchEntries(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> searchFunction) {
if (searchFunction == null) throw new NullPointerException();
return new SearchEntriesTask<K,new <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U>()).invoke();
}
/**
* @since 1.8
*/
public Map.Entry<K,V> reduceEntries(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,BiFunction<Map.Entry<K,Map.Entry<K,? extends Map.Entry<K,V>> reducer) {
if (reducer == null) throw new NullPointerException();
return new ReduceEntriesTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public <U> U reduceEntries(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,? extends U> reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceEntriesTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public double reduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>uble(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<Map.Entry<K,V>> transformer,DoubleBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public long reduceEntriesToLong(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToLongFunction<Map.Entry<K,LongBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceEntriesToLongTask<K,reducer).invoke();
}
/**
* @since 1.8
*/
public int reduceEntriesToInt(long p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>llelismThreshold,ToIntFunction<Map.Entry<K,IntBinaryOperator reducer) {
if (transformer == null || reducer == null)
throw new NullPointerException();
return new MapReduceEntriesToIntTask<K,reducer).invoke();
}
/* ----------------视图操作 Views -------------- */
/**
* Base class for views.
*/
abstract static class CollectionView<K,E>
implements Collection<E>,java.io.Serializable {
private static final long serialVersionUID = 7249069246763182397L;
final ConcurrentHashMap<K,V> map;
CollectionView(ConcurrentHashMap<K,V> map) { this.map = map; }
/**
* Returns the map <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> this view.
*
* @return the map <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> this view
*/
public ConcurrentHashMap<K,V> getMap() { return map; }
/**
* Removes all of the elements from this view,by removing all
* the mappings from the map <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> this view.
*/
public final void clear() { map.clear(); }
public final int size() { return map.size(); }
public final boolean isEmpty() { return map.isEmpty(); }
// implementations below rely on concrete classes supplying these
// abstract methods
/**
* Returns an i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor over the elements in this collection.
*
* <p>The returned i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor is
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
*
* @return an i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor over the elements in this collection
*/
public abstract I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<E> i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor();
public abstract boolean contains(Object o);
public abstract boolean remove(Object o);
private static final String oomeMsg = "<a href="https://www.jb51.cc/tag/required/" target="_blank">required</a> array size too large";
public final Object[] toArray() {
long sz = map.mappingCount();
if (sz > MAX_ARRAY_SIZE)
throw new OutOfMemoryError(oomeMsg);
int n = (int)sz;
Object[] r = new Object[n];
int i = 0;
for (E e : this) {
if (i == n) {
if (n >= MAX_ARRAY_SIZE)
throw new OutOfMemoryError(oomeMsg);
if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
n = MAX_ARRAY_SIZE;
else
n += (n >>> 1) + 1;
r = Arrays.<a href="https://www.jb51.cc/tag/cop/" target="_blank">cop</a>yOf(r,n);
}
r[i++] = e;
}
return (i == n) ? r : Arrays.<a href="https://www.jb51.cc/tag/cop/" target="_blank">cop</a>yOf(r,i);
}
@SuppressWarnings("unchecked")
public final <T> T[] toArray(T[] a) {
long sz = map.mappingCount();
if (sz > MAX_ARRAY_SIZE)
throw new OutOfMemoryError(oomeMsg);
int m = (int)sz;
T[] r = (a.length >= m) ? a :
(T[])<a href="https://www.jb51.cc/tag/javalang/" target="_blank">java.lang</a>.reflect.Array
.newInstance(a.getClass().getComponentType(),m);
int n = r.length;
int i = 0;
for (E e : this) {
if (i == n) {
if (n >= MAX_ARRAY_SIZE)
throw new OutOfMemoryError(oomeMsg);
if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
n = MAX_ARRAY_SIZE;
else
n += (n >>> 1) + 1;
r = Arrays.<a href="https://www.jb51.cc/tag/cop/" target="_blank">cop</a>yOf(r,n);
}
r[i++] = (T)e;
}
if (a == r && i < n) {
r[i] = null; // null-terminate
return r;
}
return (i == n) ? r : Arrays.<a href="https://www.jb51.cc/tag/cop/" target="_blank">cop</a>yOf(r,i);
}
public final String toString() {
StringBuilder sb = new StringBuilder();
sb.append('[');
I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<E> it = i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor();
if (it.hasNext()) {
for (;;) {
Object e = it.next();
sb.append(e == this ? "(this Collection)" : e);
if (!it.hasNext())
break;
sb.append(',').append(' ');
}
}
return sb.append(']').toString();
}
public final boolean containsAll(Collection<?> c) {
if (c != this) {
for (Object e : c) {
if (e == null || !contains(e))
return false;
}
}
return true;
}
public final boolean removeAll(Collection<?> c) {
if (c == null) throw new NullPointerException();
boolean modified = false;
for (I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<E> it = i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(); it.hasNext();) {
if (c.contains(it.next())) {
it.remove();
modified = true;
}
}
return modified;
}
public final boolean retainAll(Collection<?> c) {
if (c == null) throw new NullPointerException();
boolean modified = false;
for (I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<E> it = i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(); it.hasNext();) {
if (!c.contains(it.next())) {
it.remove();
modified = true;
}
}
return modified;
}
}
/**
* ConcurrentHashMap键的集合视图，通过映射到<a href="https://www.jb51.cc/tag/yige/" target="_blank">一个</a>公共值,<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>操作可以具有选择性。
* 这个类不能直接实例化。
* @since 1.8
*/
public static class KeySetView<K,V> extends CollectionView<K,K>
implements Set<K>,java.io.Serializable {
private static final long serialVersionUID = 7249069246763182397L;
private final V value;
KeySetView(ConcurrentHashMap<K,V> map,V value) { // non-public
super(map);
this.value = value;
}
/**
* Returns the default mapped value for additions,* or {@code null} if additions are not supported.
*
* @return the default mapped value for additions,or {@code null}
* if not supported
*/
public V getMappedValue() { return value; }
/**
* {@inheritDoc}
* @throws NullPointerException if the specified key is null
*/
public boolean contains(Object o) { return map.containsKey(o); }
/**
* Removes the key from this map view,by removing the key (and its
* corresponding value) from the <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> map. This method does
* <a href="https://www.jb51.cc/tag/nothing/" target="_blank">nothing</a> if the key is not in the map.
*
* @p<a href="https://www.jb51.cc/tag/ara/" target="_blank">ara</a>m o the key to be removed from the <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> map
* @return {@code true} if the <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> map contained the specified key
* @throws NullPointerException if the specified key is null
*/
public boolean remove(Object o) { return map.remove(o) != null; }
/**
* @return an i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor over the keys of the <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> map
*/
public I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K> i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
Node<K,V>[] t;
ConcurrentHashMap<K,V> m = map;
int f = (t = m.table) == null ? 0 : t.length;
return new KeyI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,m);
}
//<a href="https://www.jb51.cc/tag/tianjia/" target="_blank">添加</a>指定key,此时value为定义的<a href="https://www.jb51.cc/tag/mo/" target="_blank">默</a>认映射值
public boolean add(K e) {
V v;
if ((v = value) == null)
throw new UnsupportedOperationException();
return map.putVal(e,true) == null;
}
public boolean addAll(Collection<? extends K> c) {
boolean added = false;
V v;
if ((v = value) == null)
throw new UnsupportedOperationException();
for (K e : c) {
if (map.putVal(e,true) == null)
added = true;
}
return added;
}
public int hashCode() {
int h = 0;
for (K e : this)
h += e.hashCode();
return h;
}
public boolean equals(Object o) {
Set<?> c;
return ((o instanceof Set) &&
((c = (Set<?>)o) == this ||
(containsAll(c) && c.containsAll(this))));
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K> spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
Node<K,V> m = map;
long n = m.sumCount();
int f = (t = m.table) == null ? 0 : t.length;
return new KeySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,n < 0L ? 0L : n);
}
public void forEach(Consumer<? super K> action) {
if (action == null) throw new NullPointerException();
Node<K,V>[] t;
if ((t = map.table) != null) {
Traverser<K,t.length);
for (Node<K,V> p; (p = it.advance()) != null; )
action.accept(p.key);
}
}
}
/**
* A view of a ConcurrentHashMap as a {@link Collection} of
* values,in which additions are <a href="https://www.jb51.cc/tag/dis/" target="_blank">dis</a>abled. This class cannot be
* directly instantiated. See {@link #values()}.
*/
static final class ValuesView<K,V>
implements Collection<V>,java.io.Serializable {
private static final long serialVersionUID = 2249069246763182397L;
ValuesView(ConcurrentHashMap<K,V> map) { super(map); }
public final boolean contains(Object o) {
return map.containsValue(o);
}
public final boolean remove(Object o) {
if (o != null) {
for (I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V> it = i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor(); it.hasNext();) {
if (o.equals(it.next())) {
it.remove();
return true;
}
}
}
return false;
}
public final I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V> i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
ConcurrentHashMap<K,V> m = map;
Node<K,V>[] t;
int f = (t = m.table) == null ? 0 : t.length;
return new ValueI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,m);
}
public final boolean add(V e) {
throw new UnsupportedOperationException();
}
public final boolean addAll(Collection<? extends V> c) {
throw new UnsupportedOperationException();
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<V> spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
Node<K,V> m = map;
long n = m.sumCount();
int f = (t = m.table) == null ? 0 : t.length;
return new ValueSpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,n < 0L ? 0L : n);
}
public void forEach(Consumer<? super V> action) {
if (action == null) throw new NullPointerException();
Node<K,V> p; (p = it.advance()) != null; )
action.accept(p.val);
}
}
}
/**
* A view of a ConcurrentHashMap as a {@link Set} of (key,value)
* entries. This class cannot be directly instantiated. See
* {@link #entrySet()}.
*/
static final class EntrySetView<K,V>>
implements Set<Map.Entry<K,V>>,java.io.Serializable {
private static final long serialVersionUID = 2249069246763182397L;
EntrySetView(ConcurrentHashMap<K,V> map) { super(map); }
public boolean contains(Object o) {
Object k,r; Map.Entry<?,?>)o).getKey()) != null &&
(r = map.get(k)) != null &&
(v = e.getValue()) != null &&
(v == r || v.equals(r)));
}
public boolean remove(Object o) {
Object k,?>)o).getKey()) != null &&
(v = e.getValue()) != null &&
map.remove(k,v));
}
/**
* @return an i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor over the entries of the <a href="https://www.jb51.cc/tag/backing/" target="_blank">backing</a> map
*/
public I<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<Map.Entry<K,V>> i<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
ConcurrentHashMap<K,V>[] t;
int f = (t = m.table) == null ? 0 : t.length;
return new EntryI<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,m);
}
public boolean add(Entry<K,V> e) {
return map.putVal(e.getKey(),false) == null;
}
public boolean addAll(Collection<? extends Entry<K,V>> c) {
boolean added = false;
for (Entry<K,V> e : c) {
if (add(e))
added = true;
}
return added;
}
public final int hashCode() {
int h = 0;
Node<K,V> p; (p = it.advance()) != null; ) {
h += p.hashCode();
}
}
return h;
}
public final boolean equals(Object o) {
Set<?> c;
return ((o instanceof Set) &&
((c = (Set<?>)o) == this ||
(containsAll(c) && c.containsAll(this))));
}
public Spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<Map.Entry<K,V>> spli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor() {
Node<K,V> m = map;
long n = m.sumCount();
int f = (t = m.table) == null ? 0 : t.length;
return new EntrySpli<a href="https://www.jb51.cc/tag/tera/" target="_blank">tera</a>tor<K,n < 0L ? 0L : n,m);
}
public void forEach(Consumer<? super Map.Entry<K,V> p; (p = it.advance()) != null; )
action.accept(new MapEntry<K,map));
}
}
}
// -------------------------------------------------------
//批量任务的基类。从类Traverser重复一些字段和<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>，因为我们需要子类CountedCompleter。
@SuppressWarnings("serial")
abstract static class BulkTask<K,R> extends CountedCompleter<R> {
Node<K,V>[] tab; // same as Traverser
Node<K,V> next;
TableStack<K,spare;
int index;
int baseIndex;
int baseLimit;
final int baseSize;
int batch; // split control
BulkTask(BulkTask<K,?> par,int b,int f,V>[] t) {
super(par);
this.batch = b;
this.index = this.baseIndex = i;
if ((this.tab = t) == null)
this.baseSize = this.baseLimit = 0;
else if (par == null)
this.baseSize = this.baseLimit = t.length;
else {
this.baseLimit = f;
this.baseSize = par.baseSize;
}
}
/**
* Same as Traverser version
*/
final Node<K,n;
if (e != null)
return next = e;
if (baseIndex >= baseLimit || (t = tab) == null ||
(n = t.length) <= (i = index) || i < 0)
return next = null;
if ((e = tabAt(t,V>)e).f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>t;
else
e = null;
}
if (stack != null)
recoverState(n);
else if ((index = i + baseSize) >= n)
index = ++baseIndex;
}
}
private void pushState(Node<K,V> s = spare;
if (s != null)
spare = s.next;
else
s = new TableStack<K,V>();
s.tab = t;
s.length = n;
s.index = i;
s.next = stack;
stack = s;
}
private void recoverState(int n) {
TableStack<K,V> next = s.next;
s.next = spare; // save for reuse
stack = next;
spare = s;
}
if (s == null && (index += baseSize) >= n)
index = ++baseIndex;
}
}
/*
* 任务类。使用常规
* 由于编译器无法知道我们已经对任务参数进行了空值检查，因此我们强制使用最简单的提升旁路来帮助避免复杂检查。
*/
@SuppressWarnings("serial")
static final class ForEachKeyTask<K,V>
extends BulkTask<K,Void> {
final Consumer<? super K> action;
ForEachKeyTask
(BulkTask<K,?> p,Consumer<? super K> action) {
super(p,b,t);
this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Consumer<? super K> action;
if ((action = this.action) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachKeyTask<K,V>
(this,batch >>>= 1,tab,action).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
for (Node<K,V> p; (p = advance()) != null;)
action.accept(p.key);
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachValueTask<K,Void> {
final Consumer<? super V> action;
ForEachValueTask
(BulkTask<K,Consumer<? super V> action) {
super(p,t);
this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Consumer<? super V> action;
if ((action = this.action) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachValueTask<K,V> p; (p = advance()) != null;)
action.accept(p.val);
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachEntryTask<K,Void> {
final Consumer<? super Entry<K,V>> action;
ForEachEntryTask
(BulkTask<K,Consumer<? super Entry<K,V>> action) {
super(p,t);
this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Consumer<? super Entry<K,V>> action;
if ((action = this.action) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachEntryTask<K,V> p; (p = advance()) != null; )
action.accept(p);
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachMappingTask<K,Void> {
final BiConsumer<? super K,? super V> action;
ForEachMappingTask
(BulkTask<K,? super V> action) {
super(p,t);
this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiConsumer<? super K,? super V> action;
if ((action = this.action) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachMappingTask<K,V> p; (p = advance()) != null; )
action.accept(p.key,p.val);
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachTransformedKeyTask<K,U>
extends BulkTask<K,Void> {
final Function<? super K,? extends U> transformer;
final Consumer<? super U> action;
ForEachTransformedKeyTask
(BulkTask<K,Consumer<? super U> action) {
super(p,t);
this.transformer = transformer; this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super K,? extends U> transformer;
final Consumer<? super U> action;
if ((transformer = this.transformer) != null &&
(action = this.action) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachTransformedKeyTask<K,U>
(this,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p.key)) != null)
action.accept(u);
}
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachTransformedValueTask<K,Void> {
final Function<? super V,? extends U> transformer;
final Consumer<? super U> action;
ForEachTransformedValueTask
(BulkTask<K,t);
this.transformer = transformer; this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super V,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachTransformedValueTask<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p.val)) != null)
action.accept(u);
}
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachTransformedEntryTask<K,Void> {
final Function<Map.Entry<K,? extends U> transformer;
final Consumer<? super U> action;
ForEachTransformedEntryTask
(BulkTask<K,t);
this.transformer = transformer; this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<Map.Entry<K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachTransformedEntryTask<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p)) != null)
action.accept(u);
}
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class ForEachTransformedMappingTask<K,Void> {
final BiFunction<? super K,? extends U> transformer;
final Consumer<? super U> action;
ForEachTransformedMappingTask
(BulkTask<K,t);
this.transformer = transformer; this.action = action;
}
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<? super K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
new ForEachTransformedMappingTask<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p.key,p.val)) != null)
action.accept(u);
}
propagateCompletion();
}
}
}
@SuppressWarnings("serial")
static final class SearchKeysTask<K,U> {
final Function<? super K,? extends U> searchFunction;
final <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result;
SearchKeysTask
(BulkTask<K,? extends U> searchFunction,<a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result) {
super(p,t);
this.searchFunction = searchFunction; this.result = result;
}
public final U getRawResult() { return result.get(); }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super K,? extends U> searchFunction;
final <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result;
if ((searchFunction = this.searchFunction) != null &&
(result = this.result) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
if (result.get() != null)
return;
addToPendingCount(1);
new SearchKeysTask<K,result).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
while (result.get() == null) {
U u;
Node<K,V> p;
if ((p = advance()) == null) {
propagateCompletion();
break;
}
if ((u = searchFunction.apply(p.key)) != null) {
if (result.compareAndSet(null,u))
quietlyCompleteRoot();
break;
}
}
}
}
}
@SuppressWarnings("serial")
static final class SearchValuesTask<K,U> {
final Function<? super V,? extends U> searchFunction;
final <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result;
SearchValuesTask
(BulkTask<K,t);
this.searchFunction = searchFunction; this.result = result;
}
public final U getRawResult() { return result.get(); }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super V,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
if (result.get() != null)
return;
addToPendingCount(1);
new SearchValuesTask<K,V> p;
if ((p = advance()) == null) {
propagateCompletion();
break;
}
if ((u = searchFunction.apply(p.val)) != null) {
if (result.compareAndSet(null,u))
quietlyCompleteRoot();
break;
}
}
}
}
}
@SuppressWarnings("serial")
static final class SearchEntriesTask<K,U> {
final Function<Entry<K,? extends U> searchFunction;
final <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result;
SearchEntriesTask
(BulkTask<K,Function<Entry<K,t);
this.searchFunction = searchFunction; this.result = result;
}
public final U getRawResult() { return result.get(); }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<Entry<K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
if (result.get() != null)
return;
addToPendingCount(1);
new SearchEntriesTask<K,V> p;
if ((p = advance()) == null) {
propagateCompletion();
break;
}
if ((u = searchFunction.apply(p)) != null) {
if (result.compareAndSet(null,u))
quietlyCompleteRoot();
return;
}
}
}
}
}
@SuppressWarnings("serial")
static final class SearchMappingsTask<K,U> {
final BiFunction<? super K,? extends U> searchFunction;
final <a href="https://www.jb51.cc/tag/atomicreference/" target="_blank">atomicreference</a><U> result;
SearchMappingsTask
(BulkTask<K,t);
this.searchFunction = searchFunction; this.result = result;
}
public final U getRawResult() { return result.get(); }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<? super K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
if (result.get() != null)
return;
addToPendingCount(1);
new SearchMappingsTask<K,V> p;
if ((p = advance()) == null) {
propagateCompletion();
break;
}
if ((u = searchFunction.apply(p.key,p.val)) != null) {
if (result.compareAndSet(null,u))
quietlyCompleteRoot();
break;
}
}
}
}
}
@SuppressWarnings("serial")
static final class ReduceKeysTask<K,K> {
final BiFunction<? super K,? extends K> reducer;
K result;
ReduceKeysTask<K,V> rights,nextRight;
ReduceKeysTask
(BulkTask<K,ReduceKeysTask<K,V> nextRight,? extends K> reducer) {
super(p,t); this.nextRight = nextRight;
this.reducer = reducer;
}
public final K getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<? super K,? extends K> reducer;
if ((reducer = this.reducer) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new ReduceKeysTask<K,rights,reducer)).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
K r = null;
for (Node<K,V> p; (p = advance()) != null; ) {
K u = p.key;
r = (r == null) ? u : u == null ? r : reducer.apply(r,u);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
ReduceKeysTask<K,V>
t = (ReduceKeysTask<K,V>)c,s = t.rights;
while (s != null) {
K tr,sr;
if ((sr = s.result) != null)
t.result = (((tr = t.result) == null) ? sr :
reducer.apply(tr,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class ReduceValuesTask<K,V> {
final BiFunction<? super V,? extends V> reducer;
V result;
ReduceValuesTask<K,nextRight;
ReduceValuesTask
(BulkTask<K,ReduceValuesTask<K,? extends V> reducer) {
super(p,t); this.nextRight = nextRight;
this.reducer = reducer;
}
public final V getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<? super V,? extends V> reducer;
if ((reducer = this.reducer) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new ReduceValuesTask<K,reducer)).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
V r = null;
for (Node<K,V> p; (p = advance()) != null; ) {
V v = p.val;
r = (r == null) ? v : reducer.apply(r,v);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
ReduceValuesTask<K,V>
t = (ReduceValuesTask<K,s = t.rights;
while (s != null) {
V tr,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class ReduceEntriesTask<K,V>> {
final BiFunction<Map.Entry<K,V>> reducer;
Map.Entry<K,V> result;
ReduceEntriesTask<K,nextRight;
ReduceEntriesTask
(BulkTask<K,ReduceEntriesTask<K,BiFunction<Entry<K,V>> reducer) {
super(p,t); this.nextRight = nextRight;
this.reducer = reducer;
}
public final Map.Entry<K,V> getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<Map.Entry<K,V>> reducer;
if ((reducer = this.reducer) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new ReduceEntriesTask<K,reducer)).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
Map.Entry<K,V> r = null;
for (Node<K,V> p; (p = advance()) != null; )
r = (r == null) ? p : reducer.apply(r,p);
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
ReduceEntriesTask<K,V>
t = (ReduceEntriesTask<K,s = t.rights;
while (s != null) {
Map.Entry<K,V> tr,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
//MapReduce
@SuppressWarnings("serial")
static final class MapReduceKeysTask<K,? extends U> transformer;
final BiFunction<? super U,? extends U> reducer;
U result;
MapReduceKeysTask<K,U> rights,nextRight;
MapReduceKeysTask
(BulkTask<K,MapReduceKeysTask<K,U> nextRight,? extends U> reducer) {
super(p,t); this.nextRight = nextRight;
this.transformer = transformer;
this.reducer = reducer;
}
public final U getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super K,? extends U> transformer;
final BiFunction<? super U,? extends U> reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceKeysTask<K,reducer)).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
U r = null;
for (Node<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p.key)) != null)
r = (r == null) ? u : reducer.apply(r,u);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceKeysTask<K,U>
t = (MapReduceKeysTask<K,U>)c,s = t.rights;
while (s != null) {
U tr,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceValuesTask<K,? extends U> reducer;
U result;
MapReduceValuesTask<K,nextRight;
MapReduceValuesTask
(BulkTask<K,MapReduceValuesTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.reducer = reducer;
}
public final U getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<? super V,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceValuesTask<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p.val)) != null)
r = (r == null) ? u : reducer.apply(r,u);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceValuesTask<K,U>
t = (MapReduceValuesTask<K,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceEntriesTask<K,U> {
final Function<Map.Entry<K,? extends U> reducer;
U result;
MapReduceEntriesTask<K,nextRight;
MapReduceEntriesTask
(BulkTask<K,MapReduceEntriesTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.reducer = reducer;
}
public final U getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final Function<Map.Entry<K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceEntriesTask<K,V> p; (p = advance()) != null; ) {
U u;
if ((u = transformer.apply(p)) != null)
r = (r == null) ? u : reducer.apply(r,u);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceEntriesTask<K,U>
t = (MapReduceEntriesTask<K,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceMappingsTask<K,? extends U> reducer;
U result;
MapReduceMappingsTask<K,nextRight;
MapReduceMappingsTask
(BulkTask<K,MapReduceMappingsTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.reducer = reducer;
}
public final U getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final BiFunction<? super K,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceMappingsTask<K,p.val)) != null)
r = (r == null) ? u : reducer.apply(r,u);
}
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceMappingsTask<K,U>
t = (MapReduceMappingsTask<K,sr));
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,Double> {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super K> transformer;
final DoubleBinaryOperator reducer;
final double basis;
double result;
MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,nextRight;
MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask
(BulkTask<K,MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,DoubleBinaryOperator reducer) {
super(p,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Double getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super K> transformer;
final DoubleBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
double r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,r,reducer)).<a href="https://www.jb51.cc/tag/fork/" target="_blank">fork()</a>;
}
for (Node<K,V> p; (p = advance()) != null; )
r = reducer.applyAsDouble(r,transformer.applyAsDouble(p.key));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,V>
t = (MapReduceKeysT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,s = t.rights;
while (s != null) {
t.result = reducer.applyAsDouble(t.result,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,Double> {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super V> transformer;
final DoubleBinaryOperator reducer;
final double basis;
double result;
MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,nextRight;
MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask
(BulkTask<K,MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Double getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<? super V> transformer;
final DoubleBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
double r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,transformer.applyAsDouble(p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,V>
t = (MapReduceValuesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,Double> {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<Map.Entry<K,V>> transformer;
final DoubleBinaryOperator reducer;
final double basis;
double result;
MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,nextRight;
MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask
(BulkTask<K,MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Double getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleFunction<Map.Entry<K,V>> transformer;
final DoubleBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
double r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,transformer.applyAsDouble(p));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,V>
t = (MapReduceEntriesT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,Double> {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleBiFunction<? super K,? super V> transformer;
final DoubleBinaryOperator reducer;
final double basis;
double result;
MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,nextRight;
MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask
(BulkTask<K,MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Double getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final T<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleBiFunction<? super K,? super V> transformer;
final DoubleBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
double r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,transformer.applyAsDouble(p.key,p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,V>
t = (MapReduceMappingsT<a href="https://www.jb51.cc/tag/odo/" target="_blank">odo</a>ubleTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceKeysToLongTask<K,Long> {
final ToLongFunction<? super K> transformer;
final LongBinaryOperator reducer;
final long basis;
long result;
MapReduceKeysToLongTask<K,nextRight;
MapReduceKeysToLongTask
(BulkTask<K,MapReduceKeysToLongTask<K,LongBinaryOperator reducer) {
super(p,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Long getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToLongFunction<? super K> transformer;
final LongBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
long r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceKeysToLongTask<K,V> p; (p = advance()) != null; )
r = reducer.applyAsLong(r,transformer.applyAsLong(p.key));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceKeysToLongTask<K,V>
t = (MapReduceKeysToLongTask<K,s = t.rights;
while (s != null) {
t.result = reducer.applyAsLong(t.result,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceValuesToLongTask<K,Long> {
final ToLongFunction<? super V> transformer;
final LongBinaryOperator reducer;
final long basis;
long result;
MapReduceValuesToLongTask<K,nextRight;
MapReduceValuesToLongTask
(BulkTask<K,MapReduceValuesToLongTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Long getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToLongFunction<? super V> transformer;
final LongBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
long r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceValuesToLongTask<K,transformer.applyAsLong(p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceValuesToLongTask<K,V>
t = (MapReduceValuesToLongTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceEntriesToLongTask<K,Long> {
final ToLongFunction<Map.Entry<K,V>> transformer;
final LongBinaryOperator reducer;
final long basis;
long result;
MapReduceEntriesToLongTask<K,nextRight;
MapReduceEntriesToLongTask
(BulkTask<K,MapReduceEntriesToLongTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Long getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToLongFunction<Map.Entry<K,V>> transformer;
final LongBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
long r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceEntriesToLongTask<K,transformer.applyAsLong(p));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceEntriesToLongTask<K,V>
t = (MapReduceEntriesToLongTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceMappingsToLongTask<K,Long> {
final ToLongBiFunction<? super K,? super V> transformer;
final LongBinaryOperator reducer;
final long basis;
long result;
MapReduceMappingsToLongTask<K,nextRight;
MapReduceMappingsToLongTask
(BulkTask<K,MapReduceMappingsToLongTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Long getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToLongBiFunction<? super K,? super V> transformer;
final LongBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
long r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceMappingsToLongTask<K,transformer.applyAsLong(p.key,p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceMappingsToLongTask<K,V>
t = (MapReduceMappingsToLongTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceKeysToIntTask<K,Integer> {
final ToIntFunction<? super K> transformer;
final IntBinaryOperator reducer;
final int basis;
int result;
MapReduceKeysToIntTask<K,nextRight;
MapReduceKeysToIntTask
(BulkTask<K,MapReduceKeysToIntTask<K,IntBinaryOperator reducer) {
super(p,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Integer getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToIntFunction<? super K> transformer;
final IntBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
int r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceKeysToIntTask<K,V> p; (p = advance()) != null; )
r = reducer.applyAsInt(r,transformer.applyAsInt(p.key));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceKeysToIntTask<K,V>
t = (MapReduceKeysToIntTask<K,s = t.rights;
while (s != null) {
t.result = reducer.applyAsInt(t.result,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceValuesToIntTask<K,Integer> {
final ToIntFunction<? super V> transformer;
final IntBinaryOperator reducer;
final int basis;
int result;
MapReduceValuesToIntTask<K,nextRight;
MapReduceValuesToIntTask
(BulkTask<K,MapReduceValuesToIntTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Integer getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToIntFunction<? super V> transformer;
final IntBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
int r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceValuesToIntTask<K,transformer.applyAsInt(p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceValuesToIntTask<K,V>
t = (MapReduceValuesToIntTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceEntriesToIntTask<K,Integer> {
final ToIntFunction<Map.Entry<K,V>> transformer;
final IntBinaryOperator reducer;
final int basis;
int result;
MapReduceEntriesToIntTask<K,nextRight;
MapReduceEntriesToIntTask
(BulkTask<K,MapReduceEntriesToIntTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Integer getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToIntFunction<Map.Entry<K,V>> transformer;
final IntBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
int r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceEntriesToIntTask<K,transformer.applyAsInt(p));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceEntriesToIntTask<K,V>
t = (MapReduceEntriesToIntTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
@SuppressWarnings("serial")
static final class MapReduceMappingsToIntTask<K,Integer> {
final ToIntBiFunction<? super K,? super V> transformer;
final IntBinaryOperator reducer;
final int basis;
int result;
MapReduceMappingsToIntTask<K,nextRight;
MapReduceMappingsToIntTask
(BulkTask<K,MapReduceMappingsToIntTask<K,t); this.nextRight = nextRight;
this.transformer = transformer;
this.basis = basis; this.reducer = reducer;
}
public final Integer getRawResult() { return result; }
public final void co<a href="https://www.jb51.cc/tag/mpu/" target="_blank">mpu</a>te() {
final ToIntBiFunction<? super K,? super V> transformer;
final IntBinaryOperator reducer;
if ((transformer = this.transformer) != null &&
(reducer = this.reducer) != null) {
int r = this.basis;
for (int i = baseIndex,h; batch > 0 &&
(h = ((f = baseLimit) + i) >>> 1) > i;) {
addToPendingCount(1);
(rights = new MapReduceMappingsToIntTask<K,transformer.applyAsInt(p.key,p.val));
result = r;
CountedCompleter<?> c;
for (c = f<a href="https://www.jb51.cc/tag/irs/" target="_blank">irs</a>tComplete(); c != null; c = c.nextComplete()) {
@SuppressWarnings("unchecked")
MapReduceMappingsToIntTask<K,V>
t = (MapReduceMappingsToIntTask<K,s.result);
s = t.rights = s.nextRight;
}
}
}
}
}
/*-------Unsafe mechanics------*/
/**
* unsafe<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块控制了一些<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>的<a href="https://www.jb51.cc/tag/xiugai/" target="_blank">修改</a>工作，比如最常用的SIZECTL 。
* <a href="https://www.jb51.cc/tag/zaizhe/" target="_blank">在这</a>一版本的concurrentHashMap中，大量应用来的CAS<a href="https://www.jb51.cc/tag/fangfa/" target="_blank">方法</a>进行变量、<a href="https://www.jb51.cc/tag/shuxing/" target="_blank">属性</a>的<a href="https://www.jb51.cc/tag/xiugai/" target="_blank">修改</a>工作。利用CAS进行无锁操作，可以大大提高<a href="https://www.jb51.cc/tag/xingneng/" target="_blank">性能</a>。
* static<a href="https://www.jb51.cc/tag/daima/" target="_blank">代码</a>块中:大量使用了反射
*/
private static final sun.misc.Unsafe U;
private static final long SIZECTL;
private static final long TRANSFERINDEX;
private static final long BASECOUNT;
private static final long CELLSBUSY;
private static final long CELLVALUE;
private static final long ABASE;
private static final int ASHIFT;
static {
try {
U = sun.misc.Unsafe.getUnsafe();
Class<?> k = ConcurrentHashMap.class;
SIZECTL = U.objectFieldOffset
(k.getDeclaredField("sizeCtl"));
TRANSFERINDEX = U.objectFieldOffset
(k.getDeclaredField("transferIndex"));
BASECOUNT = U.objectFieldOffset
(k.getDeclaredField("baseCount"));
CELLSBUSY = U.objectFieldOffset
(k.getDeclaredField("cellsBusy"));
Class<?> ck = CounterCell.class;
CELLVALUE = U.objectFieldOffset
(ck.getDeclaredField("value"));
Class<?> ak = Node[].class;
ABASE = U.arrayBa<a href="https://www.jb51.cc/tag/SEO/" title="SEO">SEO</a>ffset(ak);
int scale = U.arrayIndexScale(ak);
if ((scale & (scale - 1)) != 0)
throw new Error("data type scale not a power of two");
ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
} catch (Exception e) {
throw new Error(e);
}
}
}
参考：nofollow">https://blog.csdn.net/u010723709/article/details/48007881
ConcurrentHashMap源码分析（JDK1.7）
一、JDK1.7ConcurrentHashMap介绍
JDK1.7中ConcurrentHashMap底层是Segment数组，每一个Segment对象中包含一个HashEntry数组，保存的元素会封装成HashEntry对象，当遇到Hash冲突时，会形成链表
Segment继承ReentrantLock，当需要控制线程安全时，对单独的Segment进行加锁，即分段锁。
几个默认值
- DEFAULT_INITIAL_CAPACITY 默认初始化容量 16
- MAXIMUM_CAPACITY 最大容量 2的30次幂
- DEFAULT_LOAD_FACTOR 默认的负载因子 0.75
- DEFAULT_CONCURRENCY_LEVEL 并发等级 16
二：构造器
// 空参构造，调用重载的构造方法
public ConcurrentHashMap() {
//调用本类的带参构造
//DEFAULT_INITIAL_CAPACITY = 16
//DEFAULT_LOAD_FACTOR = 0.75f
//int DEFAULT_CONCURRENCY_LEVEL = 16
this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
}
// 指定数组初始化长度
public ConcurrentHashMap(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
}
// 指定数组初始化长度与默认负载因子
public ConcurrentHashMap(int initialCapacity, float loadFactor) {
this(initialCapacity, loadFactor, DEFAULT_CONCURRENCY_LEVEL);
}
// 所有参数全部指定
public ConcurrentHashMap(int initialCapacity,
float loadFactor, int concurrencyLevel) {
// 做一些数据判断
if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0)
throw new IllegalArgumentException();
if (concurrencyLevel > MAX_SEGMENTS)
concurrencyLevel = MAX_SEGMENTS;
// Find power-of-two sizes best matching arguments
int sshift = 0; // 移动的位数，用于后续计算高4位的值
int ssize = 1; // Segment数组的大小
while (ssize < concurrencyLevel) {
++sshift;
// 保证Segment大小为2的次幂，如指定concurrencyLevel 为15则 ssize为16，指定concurrencyLevel为17 则ssize为32
ssize <<= 1;
}
// 这两个值用于后面计算Segment[]的角标
this.segmentShift = 32 - sshift;
this.segmentMask = ssize - 1;
// 计算每个Segment中存储的元素个数
if (initialCapacity > MAXIMUM_CAPACITY)
initialCapacity = MAXIMUM_CAPACITY;
int c = initialCapacity / ssize;
if (c * ssize < initialCapacity)
++c;
// 每个Segment最少存储2个HashEntry对象
int cap = MIN_SEGMENT_TABLE_CAPACITY;
// 保证Segment中存储的HashEntry个数是2的次幂
while (cap < c)
cap <<= 1;
// create segments and segments[0]
// 创建一个Segment对象，作为模板，后续创建Segment对象时，属性值直接复用，不再重新计算
Segment<K,V> s0 =
new Segment<K,V>(loadFactor, (int)(cap * loadFactor),
(HashEntry<K,V>[])new HashEntry[cap]);
// 创建出底层的Segment数组
Segment<K,V>[] ss = (Segment<K,V>[])new Segment[ssize];
// 使用Unsafe类，将创建的Segment对象放入数组下标为0的位置
UNSAFE.putOrderedObject(ss, SBASE, s0); // ordered write of segments[0]
this.segments = ss;
}
// 根据已有的Map去构造
public ConcurrentHashMap(Map<? extends K, ? extends V> m) {
this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
DEFAULT_INITIAL_CAPACITY),
DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
putAll(m);
}
默认情况：在new一个ConcurrentHashMap时，底层创建了一个长度为16的Segment数组，每个Segment中保存了一个长度为2的HshEntry数组，之后保存的数据都是在HashEntry中。ConcurrentHashMap中默认元素长度为32，而不是16。
三：put方法
/**
* 保存/修改方法，可能会涉及到扩容
* 不允许存储Null键和Null值
*/
public V put(K key, V value) {
Segment<K,V> s;
if (value == null)
// 值不可以为Null
throw new NullPointerException();
// 基于key，计算hash值，计算hash值时，key若为Null会报空指针异常
int hash = hash(key);
// 取高位计算要保存的Segment数组的下标（HashEntry数组用的低位计算下标）
int j = (hash >>> segmentShift) & segmentMask;
// 如果该位置没有Segment对象，则创建一个Segment对象
if ((s = (Segment<K,V>)UNSAFE.getObject // nonvolatile; recheck
(segments, (j << SSHIFT) + SBASE)) == null) // in ensureSegment
s = ensureSegment(j);
// 调用Segmetn的put方法实现元素添加
return s.put(key, hash, value, false);
}
/**
* 返回对应索引k位置的Segment对象，没有则使用索引位置0的Segment对象创建一个
* 这里没有使用锁机制，仅依靠Unsafe类进行操作
*/
private Segment<K,V> ensureSegment(int k) {
final Segment<K,V>[] ss = this.segments;
// k索引位置对应的偏移量
long u = (k << SSHIFT) + SBASE; // raw offset
Segment<K,V> seg;
// 如果数组ss索引k的位置对应的Segment对象为null
if ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u)) == null) {
// 使用构造器初始化时生成的Segment对象作为原型
Segment<K,V> proto = ss[0]; // use segment 0 as prototype
int cap = proto.table.length;
float lf = proto.loadFactor;
int threshold = (int)(cap * lf);
HashEntry<K,V>[] tab = (HashEntry<K,V>[])new HashEntry[cap];
// 再次确认在此过程中其他线程没有将该Segment对象创建出来
if ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u))
== null) {
// recheck
Segment<K,V> s = new Segment<K,V>(lf, threshold, tab);
while ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u))
== null) {
// 使用CAS将新建的Segment对象放置在数组的该位置中，如果放置成功，则break返回，如果失败再判断其余线程有没有放置成功，循环此操作
if (UNSAFE.compareAndSwapObject(ss, u, null, seg = s))
break;
}
}
}
return seg;
}
/**
* Segment对象的put方法，加锁，然后保存值
*/
final V put(K key, int hash, V value, boolean onlyIfAbsent) {
// 尝试加锁，获取到锁则继续，获取不到则调用scanAndLockForPut方法获取锁
HashEntry<K,V> node = tryLock() ? null :
scanAndLockForPut(key, hash, value);
V oldValue;
try {
HashEntry<K,V>[] tab = table;
// 获取HashEntry数组的下标，这里用低位
int index = (tab.length - 1) & hash;
// 获取数组tab对应下标index的值，有可能为0
HashEntry<K,V> first = entryAt(tab, index);
for (HashEntry<K,V> e = first;;) {
// 获取的元素不为空
if (e != null) {
K k;
// 如果重复，覆盖
if ((k = e.key) == key ||
(e.hash == hash && key.equals(k))) {
oldValue = e.value;
if (!onlyIfAbsent) {
e.value = value;
++modCount;
}
break;
}
// 不重复，获取链表的下一个元素
e = e.next;
}
else {
if (node != null)
// 如果node在等待锁的时候已经创建出来，则采用头插法直接插入即可
node.setNext(first);
else
// 创建一个新的HashEntry，next属性指向first（头插法）
node = new HashEntry<K,V>(hash, key, value, first);
int c = count + 1;
if (c > threshold && tab.length < MAXIMUM_CAPACITY)
// 如果超过扩容阈值，进行扩容，再将node插入
rehash(node);
else
// 不扩容，直接放到Entry数组中
setEntryAt(tab, index, node);
++modCount;
count = c;
oldValue = null;
break;
}
}
} finally {
// 释放锁
unlock();
}
return oldValue;
}
/**
* 使用Unsafe将元素e放到数组tab的下标i位置处
*/
static final <K,V> void setEntryAt(HashEntry<K,V>[] tab, int i,
HashEntry<K,V> e) {
UNSAFE.putOrderedObject(tab, ((long)i << TSHIFT) + TBASE, e);
}
总结一下put流程：
- 首先判断不允许null值和null键
- 计算hash值，通过hash值的高位计算出要保存的Segment数组下标
- 判断Segment数组该下标位置是否有值，如果没有值，使用Unsafe类并自旋且使用Segment数组下标0位置的原型去创建一个Segment对象，创建对象时要判断其他线程有没有将此对象创建出来，如果获取到了其他线程创建的Segment对象，则将该对象返回
- 调用Segment对象的put方法去保存值
- 保存值时，首先尝试获得该Segment对象的锁，获取不到则自旋不停尝试获取锁，在此过程中会将要保存的值封装成一个HashEntry对象，节省之后的时间，如果自旋重试一定次数（64/1）后，不再自旋，强制加锁，阻塞等待锁
- 获取锁以后，先计算该值应该保存在Segment的HashEntry数组的哪一个位置，采用低位进行计算
- 获取HashEntry数组对应下标的值，记为first
- 遍历该位置的链表，如果first为null或者遍历完都不重复，则插入（头插法），插入时，如果在自旋获取锁时已经创建好HashEntry对象，直接使用，未创建好则去创建。如果在遍历链表过程中，找到重复的元素，进行替换。
- 在插入过程中，先判断是否需要扩容，需要扩容则进行扩容，扩容完将该元素插入到新数组中，不需要扩容则将此元素放到头结点。
- 最终释放锁
四：resize()扩容
扩容只针对加锁的单个Segment的HashEntry数组进行扩容，HashEntry数组大小变成2倍，但仅局限于当前的Segment，其余Segment中的HashEntry数组大小不会变化，另外，Segment数组大小在初始化以后也不会发生变化。
/**
* 扩容方法，扩容2倍，将
*/
private void rehash(HashEntry<K,V> node) {
HashEntry<K,V>[] oldTable = table;
int oldCapacity = oldTable.length;
// 扩容2倍
int newCapacity = oldCapacity << 1;
threshold = (int)(newCapacity * loadFactor);
// 创建一个新的HashEntry数组
HashEntry<K,V>[] newTable =
(HashEntry<K,V>[]) new HashEntry[newCapacity];
int sizeMask = newCapacity - 1;
// 进行数据迁移，将旧数组上面的
for (int i = 0; i < oldCapacity ; i++) {
HashEntry<K,V> e = oldTable[i];
if (e != null) {
HashEntry<K,V> next = e.next;
// 计算新数组的下标
int idx = e.hash & sizeMask;
if (next == null) // Single node on list
// 该位置只有一个元素，直接放过去
newTable[idx] = e;
else {
// Reuse consecutive sequence at same slot
HashEntry<K,V> lastRun = e;
int lastIdx = idx;
for (HashEntry<K,V> last = next;
last != null;
last = last.next) {
// lastRun机制，对数据转移进行了一点优化，获取该位置最后计算出在新数组位置连续的元素，整体转移到新数组中去
int k = last.hash & sizeMask;
if (k != lastIdx) {
lastIdx = k;
lastRun = last;
}
}
newTable[lastIdx] = lastRun;
// Clone remaining nodes
// 转移剩余的元素，从原数组的头结点开始，到原数组的lastRun结点
for (HashEntry<K,V> p = e; p != lastRun; p = p.next) {
V v = p.value;
int h = p.hash;
int k = h & sizeMask;
HashEntry<K,V> n = newTable[k];
newTable[k] = new HashEntry<K,V>(h, p.key, v, n);
}
}
}
}
// 将新的元素采用头插法插入到新数组中
int nodeIndex = node.hash & sizeMask; // add the new node
node.setNext(newTable[nodeIndex]);
newTable[nodeIndex] = node;
// 将新数组赋值给Segment对象的HashEntry数组属性
table = newTable;
}
resize()方法总结：
- 因为是在put方法中，已经获取到lock，所以可以确保线程安全
- 扩容时首先生成一个新的数组，大小为原数组的2倍
- 将原数组的元素迁移到新数组中，遍历原HashEntry数组，获取到每一个位置的HashEntry链表
- 计算原数据应该转移到新数组的下标，如果原HashEntry链表只有一个元素，直接转移到新链表
- 如果有多个，采用lastRun机制，先获取最后几个在新数组连续的元素，先转移过去
- 之后遍历剩余的链表，根据原HashEntry元素生成新的HashEntry对象，并采用头插法放到新数组中
- 数据转移完之后，将新的元素再计算下标之后，头插法放到新数组中
- 将新数组更新到Segment对象中
六：get方法
public V get(Object key) {
Segment<K,V> s; // manually integrate access methods to reduce overhead
HashEntry<K,V>[] tab;
// 如果key为null，在这一步会抛异常
int h = hash(key);
long u = (((h >>> segmentShift) & segmentMask) << SSHIFT) + SBASE;
// 获取Segment数组对应下标的Segment对象以及该Segment对象的HashEntry数组，并且两者都不为空
if ((s = (Segment<K,V>)UNSAFE.getObjectVolatile(segments, u)) != null &&
(tab = s.table) != null) {
// 获取HashEntry数组对应下标的链表，遍历获取值
for (HashEntry<K,V> e = (HashEntry<K,V>) UNSAFE.getObjectVolatile
(tab, ((long)(((tab.length - 1) & h)) << TSHIFT) + TBASE);
e != null; e = e.next) {
K k;
if ((k = e.key) == key || (e.hash == h && key.equals(k)))
return e.value;
}
}
return null;
}
get方法总结：
- 先计算获取该key对应哪一个Segment对象（key若为null，则空指针）
- 再计算该key对应Segment对象的哪一个HashEntry链表
- 遍历链表获取值
- 这几步有任一步骤获取不到值，返回null。
七：size方法
/**
* 获取ConcurrentHashMap的大小
* 先计算两遍，看一下两遍计算的值是否相等，若相等则返回
* 若两次计算结果不一致，则再计算一遍并比较
* 若再次计算以后结果与上一次计算结果还不一致，则加锁计算
*/
public int size() {
// Try a few times to get accurate count. On failure due to
// continuous async changes in table, resort to locking.
final Segment<K,V>[] segments = this.segments;
int size;
boolean overflow; // true if size overflows 32 bits
long sum; // sum of modCounts
long last = 0L; // previous sum
int retries = -1; // first iteration isn''t retry
try {
for (;;) {
// 先比较再自加，RETRIES_BEFORE_LOCK为2
// -1 0 1 共循环三次
if (retries++ == RETRIES_BEFORE_LOCK) {
// 对每一个Segment进行加锁
for (int j = 0; j < segments.length; ++j)
ensureSegment(j).lock(); // force creation
}
sum = 0L;
size = 0;
overflow = false;
for (int j = 0; j < segments.length; ++j) {
Segment<K,V> seg = segmentAt(segments, j);
if (seg != null) {
sum += seg.modCount;
int c = seg.count;
// 计算每一个segment的count之和
if (c < 0 || (size += c) < 0)
overflow = true;
}
}
// 如果连续两次计算值一致，则返回
if (sum == last)
break;
// 修改次数之和不一致，将此次计算结果记为last，再计算一遍
last = sum;
}
} finally {
if (retries > RETRIES_BEFORE_LOCK) {
// 如果已经加锁，则释放锁
for (int j = 0; j < segments.length; ++j)
segmentAt(segments, j).unlock();
}
}
return overflow ? Integer.MAX_VALUE : size;
}
size方法总结：
- 因为在计算ConcurrentHashMap的size时，有可能会并发插入/删除数据
- 首先不加锁，计算两次所有Segment对象的modCount之和，判断是否一致，如果不一致再循环计算一次
- 如果再循环一次计算的和与之前计算还不一致，就加锁进行计算，这里加锁前最多计算三次。
结语：还在学习过程中，做一个学习记录，如有不对的地方，欢迎批评指正。
ConcurrentHashMap源码分析（一）
属性
// 最大容量 2的30次方
private static final int MAXIMUM_CAPACITY = 1 << 30;
// 默认容量16
private static final int DEFAULT_CAPACITY = 16;
// 最大的数组长度 integer的最大长度减8，8这部分存放的是对象头，其中包括数组的长度，具体可了解jvm对象头的相关内容
static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
// 并发级别，这个字段没有使用，定义来兼容以前的版本
private static final int DEFAULT_CONCURRENCY_LEVEL = 16;
// 负载因子，当元素个数大于最大容量*负载因子时，需要扩容
private static final float LOAD_FACTOR = 0.75f;
// 链表转为红黑树的阈值，超过8由链表转为红黑树
static final int TREEIFY_THRESHOLD = 8;
// 树转链表的阈值，小于等于6 树转链表
static final int UNTREEIFY_THRESHOLD = 6;
static final int MIN_TREEIFY_CAPACITY = 64;
private static final int MIN_TRANSFER_STRIDE = 16;
private static int RESIZE_STAMP_BITS = 16;
private static final int MAX_RESIZERS = (1 << (32 - RESIZE_STAMP_BITS)) - 1;
private static final int RESIZE_STAMP_SHIFT = 32 - RESIZE_STAMP_BITS;
static final int MOVED = -1;
static final int TREEBIN = -2;
static final int RESERVED = -3;
static final int HASH_BITS = 0x7fffffff;
static final int NCPU = Runtime.getRuntime().availableProcessors();
private static final ObjectStreamField[] serialPersistentFields = {
new ObjectStreamField("segments", Segment[].class),
new ObjectStreamField("segmentMask", Integer.TYPE),
new ObjectStreamField("segmentShift", Integer.TYPE)
};
// 数组，在第一次插入的时候才会初始化，数组长度总是2的n次幂
transient volatile Node<K,V>[] table;
// 下一个数组，只有当调整size的时候才非空
private transient volatile Node<K,V>[] nextTable;
// 基本的计数器，通常在没有争用的时候使用，但也用于在初始化争用是的回退，通常通过CAS更新值
private transient volatile long baseCount;
// table初始化和resizing控制
// -1：表示正在初始化
// -（1+threads)：表示当前有threads个线程正在扩容
// 当非负时
// 如果数组为null,表示数组创建数组的长度
// 如果是0,表示默认值，会在初始化的时候使用
// 如果数组不是null，表示下一次扩容的阈值
private transient volatile int sizeCtl;
private transient volatile int transferIndex;
private transient volatile int cellsBusy;
private transient volatile CounterCell[] counterCells;
private transient KeySetView<K,V> keySet;
private transient ValuesView<K,V> values;
private transient EntrySetView<K,V> entrySet;
构造方法
/**
* 空构造，初始化容量16
*/
public ConcurrentHashMap() {
}
/**
* 指定容量
*/
public ConcurrentHashMap(int initialCapacity) {
if (initialCapacity < 0)
throw new IllegalArgumentException();
int cap = ((initialCapacity >= (MAXIMUM_CAPACITY >>> 1)) ?
MAXIMUM_CAPACITY :
// tableSizeFor用来返回一个大于initialCapacity且最接近2的n次幂的值，比如initialCapacity=6，返回16
tableSizeFor(initialCapacity + (initialCapacity >>> 1) + 1));
this.sizeCtl = cap;
}
/**
* 给定一个map
*/
public ConcurrentHashMap(Map<? extends K, ? extends V> m) {
this.sizeCtl = DEFAULT_CAPACITY;
putAll(m);
}
/**
* 给定初始化大小和负载因子
*/
public ConcurrentHashMap(int initialCapacity, float loadFactor) {
this(initialCapacity, loadFactor, 1);
}
/**
* 给定初始容量、负载因子和并发级别
*/
public ConcurrentHashMap(int initialCapacity,
float loadFactor, int concurrencyLevel) {
if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0)
throw new IllegalArgumentException();
if (initialCapacity < concurrencyLevel) // Use at least as many bins
initialCapacity = concurrencyLevel; // as estimated threads
long size = (long)(1.0 + (long)initialCapacity / loadFactor);
int cap = (size >= (long)MAXIMUM_CAPACITY) ?
MAXIMUM_CAPACITY : tableSizeFor((int)size);
this.sizeCtl = cap;
}
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