【笔记】Java闭锁

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前言

java.util.concurrent.CountDownLatch类是一个并发构造，它允许许多一个或多个线程等待一系列指定操作的完成
CountDownLatch以一个给定的数量初始化，countDown()方法每调用一次，CountDownLatch的数量就减一，通过调用await()方法，线程可以阻塞等待这一数量到达零

创建一些类

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class MaiGuo implements Runnable {

    private CountDownLatch countDownLatch;

    public MaiGuo(CountDownLatch countDownLatch) {
        this.countDownLatch = countDownLatch;
    }
    
    @Override
    public void run() {
        System.out.println("锅买完了");
        // 此方法每次调用，闭锁的计数器会减1
        countDownLatch.countDown();
    }
}

class MaiCai implements Runnable {

    private CountDownLatch countDownLatch;

    public MaiGuo(CountDownLatch countDownLatch) {
        this.countDownLatch = countDownLatch;
    }
    
    @Override
    public void run() {
        System.out.println("菜买完了");
        // 此方法每次调用，闭锁的计数器会减1
        countDownLatch.countDown();
    }
}

在主方法中创建并使用闭锁

<num>：等待的线程的数量

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public static void main(String[] args) throws Exception {
    // 创建闭锁对象
    CountDownLatch countDownLatch = new CountDownLatch(<num>);
    new Thread(new MaiGuo(countDownLatch)).start();
    new Thread(new MaiCai(countDownLatch)).start();
    // 此方法产生阻塞，阻塞的开放条件是闭锁的计数器等于0
    countDownLatch.await();
    System.out.println("开始做菜");
}

完成