java.util.concurrent包中的Exchanger类可用于两个线程之间交换信息。可简单地将Exchanger对象理解为一个包含两个格子的容器，通过exchanger方法可以向两个格子中填充信息。当两个格子中的均被填充时，该对象会自动将两个格子的信息交换，然后返回给线程，从而实现两个线程的信息交换。

    示例代码如下：

package test;

import java.util.concurrent.Exchanger;

class ExchangerTest extends Thread {
    private Exchanger<String> exchanger;
    private String string;
    private String threadName;

    public ExchangerTest(Exchanger<String> exchanger, String string,
            String threadName) {
        this.exchanger = exchanger;
        this.string = string;
        this.threadName = threadName;
    }

    public void run() {
        try {
            System.out.println(threadName + ": " + exchanger.exchange(string));
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

public class Test {
    public static void main(String[] args) {
        Exchanger<String> exchanger = new Exchanger<>();
        ExchangerTest test1 = new ExchangerTest(exchanger, "string1",
                "thread-1");
        ExchangerTest test2 = new ExchangerTest(exchanger, "string2",
                "thread-2");

        test1.start();
        test2.start();
    }
}

此程序创建了两个线程，线程在执行过程中，调用同一个exchanger对象的exchange方法，进行信息通信，当两个线程均已将信息放入到exchanger对象中时，exchanger对象会将两个线程放入的信息交换，然后返回，该程序的执行结果如下图：

ExchangerTest test3 = new ExchangerTest(exchanger, "string3", "thread-3");
test3.start();