线程：Exchanger同步工具

可以在对中对元素进行配对和交换的线程的同步点，类似于交易，A拿着钱到达指定地点，B拿着物品到达指定地点，相互交换，然后各自忙各自的事去了。

package ch03;

import java.util.concurrent.Exchanger;

public class ExchangerTest {

    public static void main(String[] args) {
        final Exchanger<String> changer = new Exchanger<>();
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                try{
                    String data1 = "xyy";
                    System.out.println("交换前，"+Thread.currentThread().getName()+"的数据是："+data1);
                    //等待交易
                    String afterChange = changer.exchange(data1);
                    System.out.println("交换后，"+Thread.currentThread().getName()+"的数据是："+afterChange);
                }catch (Exception e) {
                }
            }
        }).start();
        
        new Thread(new Runnable() {
            
            @Override
            public void run() {
                try{
                    String data1 = "zy";
                    System.out.println("交换前，"+Thread.currentThread().getName()+"的数据是："+data1);
                    //等待交易
                    String afterChange = changer.exchange(data1);
                    System.out.println("交换后，"+Thread.currentThread().getName()+"的数据是："+afterChange);
                }catch (Exception e) {
                }
            }
        }).start();
    }

}