@FunctionalInterface
public interface Runnable {
    /**
     * When an object implementing interface <code>Runnable</code> is used
     * to create a thread, starting the thread causes the object''s
     * <code>run</code> method to be called in that separately executing
     * thread.
     * <p>
     * The general contract of the method <code>run</code> is that it may
     * take any action whatsoever.
     *
     * @see     java.lang.Thread#run()
     */
    public abstract void run();
}

Runnable 接口应该由那些打算通过某一线程执行其实例的类来实现。类必须定义一个称为 run 的无参数方法。 

设计该接口的目的是为希望在活动时执行代码的对象提供一个公共协议。例如，Thread 类实现了 Runnable。激活的意思是说某个线程已启动并且尚未停止。 

此外，Runnable 为非 Thread 子类的类提供了一种激活方式。通过实例化某个 Thread 实例并将自身作为运行目标，
就可以运行实现 Runnable 的类而无需创建 Thread 的子类。大多数情况下，如果只想重写 run() 方法，
而不重写其他 Thread 方法，那么应使用 Runnable 接口。这很重要，因为除非程序员打算修改或增强类的基本行为，否则不应为该类创建子类。

public interface Callable<V> {
    /**
     * Computes a result, or throws an exception if unable to do so.
     *
     * @return computed result
     * @throws Exception if unable to compute a result
     */
    V call() throws Exception;
}

返回结果并且可能抛出异常的任务。实现者定义了一个不带任何参数的叫做 call 的方法。 

Callable 接口类似于 Runnable，两者都是为那些其实例可能被另一个线程执行的类设计的。但是 Runnable 不会返回结果，并且无法抛出经过检查的异常。 

Executors 类包含一些从其他普通形式转换成 Callable 类的实用方法。 

（1）Callable规定的方法是call()，而Runnable规定的方法是run()。

（2）Callable的任务执行后可返回值，而Runnable的任务是不能返回值的。

（3）call()方法可抛出异常，而run()方法是不能抛出异常的。

（4）运行Callable任务可拿到一个Future对象。

package com.zyf.Future;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

public class FutureGetTimeOut1 {  
    public static void main(String[] args){  
        int timeout = 2;   
        ExecutorService executor = Executors.newSingleThreadExecutor();  
        Boolean result = false;     
        Future<Boolean> future = executor.submit(new TaskThread("发送请求"));//将任务提交给线程池
        try {     
            result = future.get(timeout, TimeUnit.SECONDS);
           // result = future.get(timeout, TimeUnit.MILLISECONDS); //1
            System.out.println("发送请求任务的返回结果： "+result);  //2
        } catch (InterruptedException e) {  
            System.out.println("线程中断出错。");  
            future.cancel(true);// 中断执行此任务的线程     
        } catch (ExecutionException e) {     
            System.out.println("线程服务出错。");  
            future.cancel(true);
        } catch (TimeoutException e) {// 超时异常     
            System.out.println("超时。");     
            future.cancel(true);  
        }finally{  
            System.out.println("线程服务关闭。");  
            executor.shutdown();  
        }  
    }  
      
    static class TaskThread implements Callable<Boolean> {    
        private String t;  
        public TaskThread(String temp){  
            this.t= temp;  
        }  
        public Boolean call() {  
            //for用于模拟超时
            for(int i=0;i<999999999;i++){  
                if(i==999999998){  
                    System.out.println(t+"成功！");  
                }  
                if (Thread.interrupted()){ //很重要  
                    return false;     
                }  
            }   
            System.out.println("继续执行..........");     
            return true;     
        }     
    }   
}

package com.zyf.Future;

import java.util.concurrent.*;

public class FutureGetTimeOut2 {

    public static void main(String[] args) {
        final ExecutorService service = Executors.newFixedThreadPool(1);
        TaskThread taskThread = new TaskThread();
        System.out.println("提交任务...begin");
        Future<Object> taskFuture = service.submit(taskThread);
        System.out.println("提交任务...end");
        try {
            Object re = taskFuture.get(60000, TimeUnit.MILLISECONDS);// 超时设置
            System.out.println(re);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (TimeoutException e) {
            System.out.println("超时 取消任务");
            taskFuture.cancel(true);
            System.out.println("超时 取消任务OK");
        } finally {
            service.shutdown();
        }
    }
}

class TaskThread implements Callable<Object> {
    public Object call() throws Exception {
        String result = "空结果";
        try {
            System.out.println("任务开始....");
            //修改sleep 的值测试超时
            Thread.sleep(500);
            result = "正确结果";
            System.out.println("任务结束....");
        } catch (Exception e) {
            System.out.println("Task is interrupted!");
        }
        return result;
    }
}

package com.zyf.Future;

import java.util.concurrent.*;

class MyCallable implements Callable<Object> {

    private int flag = 0;

    public MyCallable(int flag) {

        this.flag = flag;

    }

    public String call() throws Exception {

        if (this.flag == 0) {

            return "flag = 0";

        }

        if (this.flag == 1) {

            try {

                while (true) {

                    System.out.println("looping.");

                    Thread.sleep(2000);

                }

            } catch (InterruptedException e) {

                System.out.println("Interrupted");

            }

            return "false";

        } else {

            throw new Exception("Bad flag value!");

        }

    }

}

public class FutureGetBlock {
    
    public static void main(String[] args) {

        // 定义3个Callable类型的任务

        MyCallable task1 = new MyCallable(0);

        MyCallable task2 = new MyCallable(1);

        MyCallable task3 = new MyCallable(2);

        // 创建一个执行任务的服务

        ExecutorService es = Executors.newFixedThreadPool(3);

        try {

            // 提交并执行任务，任务启动时返回了一个Future对象，

            // 如果想得到任务执行的结果或者是异常可对这个Future对象进行操作

            Future<?> future1 = es.submit(task1);

            // 获得第一个任务的结果，如果调用get方法，当前线程会等待任务执行完毕后才往下执行

            System.out.println("task1: " + future1.get());

            Future<?> future2 = es.submit(task2);

            // 等待5秒后，再停止第二个任务。因为第二个任务进行的是无限循环

            Thread.sleep(5000);

            System.out.println("task2 cancel: " + future2.cancel(true));

            // 获取第三个任务的输出，因为执行第三个任务会引起异常

            // 所以下面的语句将引起异常的抛出

            Future<?> future3 = es.submit(task3);

            System.out.println("task3: " + future3.get());

        } catch (Exception e) {

            System.out.println(e.toString());

        }

        // 停止任务执行服务

        es.shutdownNow();

    }

}

public class FutureTask<V> implements RunnableFuture<V>
public interface RunnableFuture<V> extends Runnable, Future<V> {
    /**
     * Sets this Future to the result of its computation
     * unless it has been cancelled.
     */
    void run();
}

public FutureTask(Callable<V> callable) {
        if (callable == null)
            throw new NullPointerException();
        this.callable = callable;
        this.state = NEW;       // ensure visibility of callable
    }

 public FutureTask(Runnable runnable, V result) {
        this.callable = Executors.callable(runnable, result);
        this.state = NEW;       // ensure visibility of callable
    }

public static <T> Callable<T> callable(Runnable task, T result) {
        if (task == null)
            throw new NullPointerException();
        return new RunnableAdapter<T>(task, result);
    }
/**
 * A callable that runs given task and returns given result
 */
static final class RunnableAdapter<T> implements Callable<T> {
        final Runnable task;
        final T result;
        RunnableAdapter(Runnable task, T result) {
            this.task = task;
            this.result = result;
        }
        public T call() {
            task.run();
            return result;
        }
    }

package com.zyf.Future;

import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

public class FutureTaskDemo {
    public static void main(String[] args) {
        Callable<Integer> callable = new Callable<Integer>() {
            public Integer call() throws Exception {
                return new Random().nextInt(100);
            }
        };

        FutureTask<Integer> future = new FutureTask<Integer>(callable);
        new Thread(future).start();

        try {
            Thread.sleep(1000);// 可能做一些事情

            int result = future.get();
            System.out.println(result);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }
}

package com.zyf.Future;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;

public class FutureTaskDemo2 {

    static ExecutorService mExecutor = Executors.newSingleThreadExecutor();

    public static void main(String[] args) {
        futureDemo();
    }

    static void futureDemo() {
        try {
            /**
             * 提交runnable则没有返回值, future没有数据
             */
            Future<?> future = mExecutor.submit(new Runnable() {

                @Override
                public void run() {
                    fibc(20);
                }
            });

            System.out.println("future result from runnable : " + future.get());

            /**
             * 提交Callable, 有返回值, future中能够获取返回值
             */
            Future<Integer> result2 = mExecutor.submit(new Callable<Integer>() {
                @Override
                public Integer call() throws Exception {
                    return fibc(20);
                }
            });

            System.out.println("future result from callable : " + result2.get());

            /**
             * FutureTask则是一个RunnableFuture<V>，即实现了Runnbale又实现了Futrue<V>这两个接口，
             * 另外它还可以包装Runnable(实际上会转换为Callable)和Callable
             * <V>，所以一般来讲是一个符合体了，它可以通过Thread包装来直接执行，也可以提交给ExecuteService来执行
             * ，并且还可以通过v get()返回执行结果，在线程体没有执行完成的时候，主线程一直阻塞等待，执行完则直接返回结果。
             */
            FutureTask<Integer> futureTask = new FutureTask<Integer>(new Callable<Integer>() {
                @Override
                public Integer call() throws Exception {
                    return fibc(20);
                }
            });
            // 提交futureTask
            mExecutor.submit(futureTask);
            System.out.println("future result from futureTask : " + futureTask.get());

            mExecutor.shutdown();

        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }

    /**
     * 效率底下的斐波那契数列, 耗时的操作
     * 
     * @param num
     * @return
     */
    static int fibc(int num) {
        if (num == 0) {
            return 0;
        }
        if (num == 1) {
            return 1;
        }
        return fibc(num - 1) + fibc(num - 2);
    }

}