如果您对JavaClone感兴趣，那么本文将是一篇不错的选择，我们将为您详在本文中，您将会了解到关于JavaClone的详细内容，我们还将为您解答vsCopy构造函数-在Java中推荐[duplica

如果您对JavaClone感兴趣，那么本文将是一篇不错的选择，我们将为您详在本文中，您将会了解到关于JavaClone的详细内容，我们还将为您解答vs Copy构造函数-在Java中推荐[duplicate]的相关问题，并且为您提供关于HOW TO GET 2ND DUPLICATE COLUMN VALUE IN JAVA、Java 8: Converting Map> to Map [duplicate]、Java Generics Copy构造函数、java-构造函数TextView(new View.OnClickListener(){})未定义的有价值信息。

• JavaClone（）vs Copy构造函数-在Java中推荐[duplicate]（java拷贝构造函数）
• HOW TO GET 2ND DUPLICATE COLUMN VALUE IN JAVA
• Java 8: Converting Map> to Map [duplicate]
• Java Generics Copy构造函数
• java-构造函数TextView(new View.OnClickListener(){})未定义

JavaClone（）vs Copy构造函数-在Java中推荐[duplicate]（java拷贝构造函数）

java中的clone方法vs复制构造函数。哪个是正确的解决方案。每种情况在哪里使用？

答案1

克隆已损坏，因此请勿使用。

Object类的CLONE方法是一种有些神奇的方法，它没有纯Java方法可以做的事情：它产生其对象的相同副本。自Java编译器的Beta版本发布以来，它就已经存在于原始Object超类中。就像所有古代魔法一样，它需要适当的咒语以防止该法术意外地反射击

首选复制对象的方法

Foo copyFoo (Foo foo){  Foo f = new Foo();  //for all properties in FOo  f.set(foo.get());  return f;}

HOW TO GET 2ND DUPLICATE COLUMN VALUE IN JAVA

HI,

          I AM FINDING DUPLICATE NAME VALUE IN JAVA . MY CODE LIKE THAT .

        ResultSet rs = dbm.getColumns(null,null,tablename)

String Dup=null;

while(rs.next)

{

String columnname = rs.getString("COLUMN_NAME");

if(Dup.contains(columnname ))

{

//Duplicate column Name i am getting but displayed first column ,, i need 2nd duplicate name.

}

Dup =Dup+columnname .Trim()+",";

}

input like : columnname    pk

                  id                  yes

                  name            yes 

 out need lke : columnname name has duplicate yes value consider , but id has duplicate columnname showing . can any one let me know .

Java 8: Converting Map> to Map [duplicate]

Map<String, Map<String, List<String>>> testMap = foos.stream().collect(Collectors.groupingBy(e -> e.getAreaName(),
        Collectors.groupingBy(e -> e.getObjectName(), Collectors.collectingAndThen(Collectors.toList(),
                e -> e.stream().map(f -> f.getLineName())))));

Map<String, List<String>> parameters;

Map<String, String[]> collect = parameters.entrySet().stream()
                .collect(Collectors.toMap(entry-> entry.getKey(),entry -> entry.getValue().toArray()));

Map<Object, Map<Object, List<Foo>>> testMap = ventures.stream().collect(Collectors.groupingBy(e -> e.getAreaName(),
        Collectors.groupingBy(e -> e.getObjectName(), Collectors.toList())));

Map<String, String[]> collect = 
    parameters.entrySet()
              .stream()
              .collect(Collectors.toMap(Map.Entry::getKey,
                                        entry -> entry.getValue().toArray(new String[0])));

Map<Long, List<Long>> maps = css.parallelStream().collect(Collectors.groupingBy(CompanyInfoEntity::getDid, Collectors.mapping(CompanyInfoEntity::getId, Collectors.toList())));

Map<Object, Map<Object, List<Foo>>> testMap = ventures.stream().collect(Collectors.groupingBy(e -> e.getAreaName(),
        Collectors.groupingBy(e -> e.getObjectName(), Collectors.toList())));

Map<String, Map<String, List<String>>> testMap = 
    foos.stream()
        .collect(Collectors.groupingBy(Foo::getAreaName,
                                       Collectors.groupingBy(Foo::getObjectName,
                                                             Collectors.mapping(Foo::getLineName,
                                                                                Collectors.toList()))));

Java Generics Copy构造函数

public class treeDB <T extends Object> {
    //methods and such

    public T patient; 
    patient = new T(patient2);       //this line throwing an error
    //where patient2 is of type <T>
}

public class Test<T> {

    public T createcopy(T item) throws Exception {// here should be
        // thrown more detailed exceptions but I decided to reduce them for
        // readability

        Class<?> clazz = item.getClass();
        Constructor<?> copyConstructor = clazz.getConstructor(clazz);

        @SuppressWarnings("unchecked")
        T copy = (T) copyConstructor.newInstance(item);

        return copy;
    }
}

//demo for MyClass that will have copy constructor: 
//         public MyClass(MyClass original)
public static void main(String[] args) throws Exception {
    MyClass mc = new MyClass("someString",42);

    Test<MyClass> test = new Test<>();
    MyClass copy = test.createcopy(mc);

    System.out.println(copy.getSomeString());
    System.out.println(copy.getSomeNumber());
}

java-构造函数TextView(new View.OnClickListener(){})未定义

我收到此错误代码构造函数TextView(new View.OnClickListener(){})未定义
请帮助我,这是我的代码,它让我难过了几天.
    `包com.example.tgtidea;

public class FrontPage extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_front_page);

    Button btn1 = (Button)findViewById(R.id.button1);
    btn1.setonClickListener(new OnClickListener() {


        public void onClick(View v) {

            EditText comment = (EditText)findViewById(R.id.editText1);
            String comment1 = comment.getText().toString();
            TextView textView = new TextView();
            textView.setTextSize(40);
            textView.setText(comment1);

        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.front_page, menu);
    return true;
}

}
` 

这不是我的全部代码,而是大部分.做了一些研究,看起来其他人也有类似的问题,只是使用Intent而不是Text View.我是一个年轻的程序员,我只有14岁,请原谅我的无知.谢谢您的帮助.

解决方法:

改变这个

TextView textView = new TextView();

至

TextView textView = new TextView(FrontPage.this); 

但是您的textView未附加到活动.在activity_frot_page中具有LinearLayout或RelativeLayout,对其进行初始化并向其添加textView,在activity_front_page中具有textView对其进行初始化并将其设置为textView

http://developer.android.com/reference/android/widget/TextView.html

查看上面链接中的公共构造函数

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