countDownLatch学习 | 易学教程

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使用匿名内部类创建线程：
new Thread(() -> {
    while (true) {
        try {
            Thread.sleep(3000);
            System.out.println("线程1开始执行…… ……");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}).start();

CountDownLatch测试

public static void main(String[] args) {
    final CountDownLatch latch = new CountDownLatch(2);
    System.out.println("主线程开始执行…… ……");
    //第一个子线程执行
    ExecutorService es1 = Executors.newSingleThreadExecutor();
    es1.execute(() -> {
        try {
            Thread.sleep(3000);
            System.out.println("子线程：" + Thread.currentThread().getName() + "执行");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        latch.countDown();
    });
    es1.shutdown();

    //第二个子线程执行
    ExecutorService es2 = Executors.newSingleThreadExecutor();
    es2.execute(() -> {
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("子线程：" + Thread.currentThread().getName() + "执行");
        latch.countDown();
    });
    es2.shutdown();
    System.out.println("等待两个线程执行完毕…… ……");
    try {
        latch.await();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    System.out.println("两个子线程都执行完毕，继续执行主线程");
}

运行结果;

主线程开始执行…… ……
等待两个线程执行完毕…… ……
子线程：pool-1-thread-1执行
子线程：pool-2-thread-1执行
两个子线程都执行完毕，继续执行主线程

模拟并发示例

public static void main(String[] args) {
        ExecutorService pool = Executors.newCachedThreadPool();
        CountDownLatch cdl = new CountDownLatch(100);
        for (int i = 0; i < 100; i++) {
            CountRunnable runnable = new CountRunnable(cdl);
            pool.execute(runnable);
        }
    }
}

class CountRunnable implements Runnable {
    private CountDownLatch countDownLatch;

    public CountRunnable(CountDownLatch countDownLatch) {
        this.countDownLatch = countDownLatch;
    }

    @Override
    public void run() {
        try {
            synchronized (countDownLatch) {
                /*** 每次减少一个容量*/
                countDownLatch.countDown();
                System.out.println("thread counts = " + (countDownLatch.getCount()));
            }
            countDownLatch.await();
            System.out.println("concurrency counts = " + (100 - countDownLatch.getCount()));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

执行结果
thread counts = 99
thread counts = 98
thread counts = 97
thread counts = 96
thread counts = 95
thread counts = 94
thread counts = 93
thread counts = 92
thread counts = 91
thread counts = 90
thread counts = 89
thread counts = 88
thread counts = 87
thread counts = 86
thread counts = 85
thread counts = 84
thread counts = 83
thread counts = 82
thread counts = 81
thread counts = 80
thread counts = 79
thread counts = 78
thread counts = 77
thread counts = 76
thread counts = 75
thread counts = 74
thread counts = 73
thread counts = 72
thread counts = 71
thread counts = 70
thread counts = 69
thread counts = 68
thread counts = 67
thread counts = 66
thread counts = 65
thread counts = 64
thread counts = 63
thread counts = 62
thread counts = 61
thread counts = 60
thread counts = 59
thread counts = 58
thread counts = 57
thread counts = 56
thread counts = 55
thread counts = 54
thread counts = 53
thread counts = 52
thread counts = 51
thread counts = 50
thread counts = 49
thread counts = 48
thread counts = 47
thread counts = 46
thread counts = 45
thread counts = 44
thread counts = 43
thread counts = 42
thread counts = 41
thread counts = 40
thread counts = 39
thread counts = 38
thread counts = 37
thread counts = 36
thread counts = 35
thread counts = 34
thread counts = 33
thread counts = 32
thread counts = 31
thread counts = 30
thread counts = 29
thread counts = 28
thread counts = 27
thread counts = 26
thread counts = 25
thread counts = 24
thread counts = 23
thread counts = 22
thread counts = 21
thread counts = 20
thread counts = 19
thread counts = 18
thread counts = 17
thread counts = 16
thread counts = 15
thread counts = 14
thread counts = 13
thread counts = 12
thread counts = 11
thread counts = 10
thread counts = 9
thread counts = 8
thread counts = 7
thread counts = 6
thread counts = 5
thread counts = 4
thread counts = 3
thread counts = 2
thread counts = 1
thread counts = 0
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
concurrency counts = 100
Disconnected from the target VM, address: '127.0.0.1:54856', transport: 'socket'

Process finished with exit code 0

来源：oschina

链接：https://my.oschina.net/u/3915790/blog/3147211

标签

countdownlatch

线程

system