本文參考至《Java7并發(fā)編程實戰(zhàn)手冊》

Exchanger類允許在兩個線程之間定義同步點，當(dāng)兩個線程都到達同步點時，它們交換數(shù)據(jù)。也就是第一個線程的數(shù)據(jù)進入到第二個線程中，第二線程的數(shù)據(jù)進入到第一個線程中。
這里有一個生產(chǎn)者和消費者的例子：生產(chǎn)者每次都會生產(chǎn)10個數(shù)據(jù)，這10個數(shù)據(jù)放在一個籮筐（List）里面，Exchanger會在：生產(chǎn)者生產(chǎn)完10個數(shù)據(jù)并且消費者消費完10個數(shù)據(jù)的時候，將兩者的籮筐換過來。這樣生產(chǎn)者的籮筐里面就沒有數(shù)據(jù)（確保生產(chǎn)者生產(chǎn)的東西有地方裝）；消費者的籮筐里面就有10個數(shù)據(jù)（確保消費者有數(shù)據(jù)消費）。

生產(chǎn)者：

package Exchanger;

import java.util.List;
import java.util.concurrent.Exchanger;

/**
 * Producer:生產(chǎn)者
 * 
 * @author JM
 * @date 2017-2-28 下午10:33:08
 * @since JDK 1.7
 */
public class Producer implements Runnable {

    private List<String> buffer;

    private final Exchanger<List<String>> exchanger;

    public Producer(List<String> buffer, Exchanger<List<String>> exchanger) {
        super();
        this.buffer = buffer;
        this.exchanger = exchanger;
    }

    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            for (int j = 0; j < 10; j++) {
                String message = "Event " + ((i * 10) + j);
                System.out.printf("Producer:create---------- %s\n", message);
                buffer.add(message);
            }
            System.out.println("Before exchange  Producer:have11111111111@@@@@@@@@@ " + buffer.size());
            try {
                // 如果這個時候消費者也剛好在這里等待，那么生產(chǎn)者和消費者的數(shù)據(jù)產(chǎn)生對換（否則將等待消費者到達這里再進行數(shù)據(jù)對換）
                buffer = exchanger.exchange(buffer);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("After exchange   Producer:have222222222222@@@@@@@@@@ " + buffer.size());
        }
    }

}

消費者：

package Exchanger;

import java.util.List;
import java.util.concurrent.Exchanger;

public class Consumer implements Runnable {
    private List<String> buffer;
    private final Exchanger<List<String>> exchanger;

    public Consumer(List<String> buffer, Exchanger<List<String>> exchanger) {
        super();
        this.buffer = buffer;
        this.exchanger = exchanger;
    }

    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println("Before exchange Consumer:have111111111******** " + buffer.size());
            try {
                // 如果這個時候生產(chǎn)者也剛好在這里等待，那么生產(chǎn)者和消費者的數(shù)據(jù)產(chǎn)生對換（否則將等待生產(chǎn)者到達這里再進行數(shù)據(jù)對換）
                buffer = exchanger.exchange(buffer);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("After exchange Consumer:have2222222******** " + buffer.size());
            for (int j = 0; j < 10; j++) {
                String message = buffer.get(0);
                System.out.printf("Consumer:use----------- %s\n", message);
                buffer.remove(0);
            }
        }
    }

}

測試類：

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Exchanger;

public class Main {
    public static void main(String[] args) {
        List<String> consumerBuffer = new ArrayList<String>();
        List<String> producerBuffer = new ArrayList<String>();
        Exchanger<List<String>> exchanger = new Exchanger<List<String>>();
        Producer producer = new Producer(producerBuffer, exchanger);
        Consumer consumer = new Consumer(consumerBuffer, exchanger);
        Thread producerThread = new Thread(producer);
        Thread consumerThread = new Thread(consumer);
        producerThread.start();
        consumerThread.start();
    }
}