Java实例学习 Java并发编程之java.util.concurrent.CountDownLatch

  CountDownLatch是一种简单的同步模式，

它让一个线程可以等待一个或多个线程完成它们的工作从而避免对临界资源并发访问所引发的各种问题。

import java.util.concurrent.CountDownLatch;
/**
 * 工人类
 */
class Worker {
    private String name;        // 名字
    private long workDuration;  // 工作持续时间


    /**
     * 构造器
     */
    public Worker(String name, long workDuration) {
        this.name = name;
        this.workDuration = workDuration;
    }


    /**
     * 完成工作
     */
    public void doWork() {
        System.out.println(name + " begins to work...");
        try {
            Thread.sleep(workDuration); // 用休眠模拟工作执行的时间
        } catch(InterruptedException ex) {
            ex.printStackTrace();
        }
        System.out.println(name + " has finished the job...");
    }
}

/**
 * 测试线程
 */
class WorkerTestThread implements Runnable {
    private Worker worker;
    private CountDownLatch cdLatch;

    public WorkerTestThread(Worker worker, CountDownLatch cdLatch) {
        this.worker = worker;
        this.cdLatch = cdLatch;
    }

    @Override
    public void run() {
        worker.doWork();        // 让工人开始工作
        cdLatch.countDown();    // 工作完成后倒计时次数减1
    }
}

public class CountDownLatchTest {

    private static final int MAX_WORK_DURATION = 5000;  // 最大工作时间
    private static final int MIN_WORK_DURATION = 1000;  // 最小工作时间

    // 产生随机的工作时间
    private static long getRandomWorkDuration(long min, long max) {
        return (long) (Math.random() * (max - min) + min);
    }

    public static void main(String[] args) {
        CountDownLatch latch = new CountDownLatch(2);   // 创建倒计时闩并指定倒计时次数为2
        Worker w1 = new Worker("骆昊", getRandomWorkDuration(MIN_WORK_DURATION, MAX_WORK_DURATION));
        Worker w2 = new Worker("王大锤", getRandomWorkDuration(MIN_WORK_DURATION, MAX_WORK_DURATION));

        new Thread(new WorkerTestThread(w1, latch)).start();
        new Thread(new WorkerTestThread(w2, latch)).start();

        try {
            latch.await();  // 等待倒计时闩减到0
            System.out.println("All jobs have been finished!");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

转载自：http://blog.csdn.net/jackfrued/article/details/44499227