并发编程丨CountDownLatch的使用小demo

CountDownLatch是java.util.concurrent包中一个类，CountDownLatch只要提供的机制是多个（具体数量等于初始化CountDownLatch时count的值）线程都达到了预期状态或者完成了预期工作时触发事件，其他线程可以等待这个事件来触发自己后续的工作。等待的线程可以是多个，即CountDownLatch可以唤醒多个等待的线程。到达自己预期状态的线程会调用CountDownLatch的countDown方法，而等待的线程会调用CountDownLatch的await方法。

什么情况下可以用这个cdl呢？我平常约朋友们打英雄联盟（5V5竞技游戏），然后总有那么一个人要在大家都上号了之后他才上号，这个情形就可以使用CDL来表示，废话不说直接上demo！

Player类作为我们提前上号的好队友，因为tx这垃圾服务器的存在，所以上号需要一定时间，这里随机数设置为等待0-10s~

public class Player implements Runnable {

    private CountDownLatch downLatch;

    private String name;

    public Player(CountDownLatch downLatch, String name) {
        this.downLatch = downLatch;
        this.name = name;
    }

    public void run() {
        this.doWork();
        try {
            TimeUnit.SECONDS.sleep(new Random().nextInt(10));
        } catch (Exception e) {
        }
        System.out.println(this.name + "已经上号了！");
        this.downLatch.countDown();

    }

    private void doWork() {
        System.out.println(this.name + "正在上号!");
    }

}

BadPlayer作为等大家都上了号以后，才上号那个拖延症坏队友

public class BadPlayer implements Runnable {

    private CountDownLatch downLatch;

    public BadPlayer(CountDownLatch downLatch){
        this.downLatch = downLatch;
    }

    public void run() {
        System.out.println("拖延症玩家等其他队友都上号.....");
        try {
            this.downLatch.await();
        } catch (Exception e) {
        }
        System.out.println("其他队友都上号了,他终于上号了~!!");
    }

}

主方法

public class CountDownLatchDemo {

    public static void main(String[] args) {
        ThreadPoolExecutor executor = new ThreadPoolExecutor(5, 5, 5, TimeUnit.SECONDS, new ArrayBlockingQueue(16));

        CountDownLatch latch = new CountDownLatch(3);

        Player p1 = new Player(latch, "盖伦");
        Player p2 = new Player(latch, "瑞兹");
        Player p3 = new Player(latch, "娑娜");
        Player p4 = new Player(latch, "赵信");

        BadPlayer badPlayer = new BadPlayer(latch);

        executor.execute(p3);
        executor.execute(p2);
        executor.execute(p1);
        executor.execute(p4);
        executor.execute(badPlayer);

        executor.shutdown();
    }

}

shift+F10执行方法

搞定~