Exchanger

　　Exchanger可以在两个线程之间交换数据，只能是2个线程，不支持更多的线程之间互换数据。

　　当线程A调用Exchange对象的exchange()方法后，他会进入阻塞状态，直到线程B也调用了exchange()方法，然后以线程安全的方式交换数据，之后线程A和B继续运行。

　　Exchanger很适合于一个生产者和一个消费者的生产者消费者模式。　

public class ThreadLocalTest {

    public static void main(String[] args) {
        Exchanger<List<Integer>> exchanger = new Exchanger<>();
        new Consumer(exchanger).start();
        new Producer(exchanger).start();
    }

}

class Producer extends Thread {
    List<Integer> list = new ArrayList<>();
    Exchanger<List<Integer>> exchanger = null;
    public Producer(Exchanger<List<Integer>> exchanger) {
        super();
        this.exchanger = exchanger;
    }
    @Override
    public void run() {
        Random rand = new Random();
        for(int i=0; i<10; i++) {
            list.clear();
            list.add(rand.nextInt(10000));
            list.add(rand.nextInt(10000));
            list.add(rand.nextInt(10000));
            list.add(rand.nextInt(10000));
            list.add(rand.nextInt(10000));
            try {
                list = exchanger.exchange(list);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

class Consumer extends Thread {
    List<Integer> list = new ArrayList<>();
    Exchanger<List<Integer>> exchanger = null;
    public Consumer(Exchanger<List<Integer>> exchanger) {
        super();
        this.exchanger = exchanger;
    }
    @Override
    public void run() {
        for(int i=0; i<10; i++) {
            try {
                list = exchanger.exchange(list);
            } catch (InterruptedException e) {                
　　　　　　e.printStackTrace();
            }
            System.out.print(list.get(0)+", ");
            System.out.print(list.get(1)+", ");
            System.out.print(list.get(2)+", ");
            System.out.print(list.get(3)+", ");
            System.out.println(list.get(4)+", ");
        }
    }
}