Exchanger是java.util.concurrent包下的一个类。通过此类可以达到两个线程之间交换对象的目的。Exchanger交换对象图如下：

交互对象通过Exchanger对象的exchange()方法完成。代码如下：

Exchanger<String> exchanger = new Exchanger<>();
ExchangeRunnable exch1 = new ExchangeRunnable(exchanger,"a");
ExchangeRunnable exch2 = new ExchangeRunnable(exchanger,"b");
new Thread(exch1).start();
new Thread(exch2).start();

ExchangeRunnable类代码如下：

public static class ExchangeRunnable implements Runnable{
    Exchanger<String> exchanger = null;
    String val = null;

    public ExchangeRunnable(Exchanger<String> exchanger,String val){
        this.exchanger = exchanger;
        this.val = val;
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        try {
            String previousStr = this.val;
            this.val = this.exchanger.exchange(this.val);
            System.out.println(Thread.currentThread().getName()+
                    " exchanged " + previousStr + " for " + this.val);

        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
     }

 }

测试结果如下：

Thread-0 exchanged a for b
Thread-1 exchanged b for a