Java并发组件一之CountDownLatch

CountDownLatch

相关文章：

1. CountDownLatch
2. CyclicBarriar--循环屏障
3. Semaphore--信号量

使用场景：

一个或N个线程，等待其它线程完成某项操作之后才能继续往下执行。CountDownLatch描述的是，一个或N个线程等待其他线程的关系。

使用方法：

1. 设CountDownLatch个数：CountDownLatch countDownLatch=new CountDownLatch(3);
2. 在等待线程中await：countDownLatch.await();
3. 在其他线程中减少count值：countDownLatch.getCount();
4. 一旦其他线程中的countDownLatch.getCount()的次数为实例化时的count值，就唤醒等待线程

/**
 * 作者:jtl
 * 日期:Created in 2019/7/29 14:59
 * 描述:CountDownLatch 例子
 * 更改:
 */

class CountDownLatchExample {
    private static final int total=200;
    
    public static void main(String[] args) throws InterruptedException{
        ExecutorService executorService = Executors.newCachedThreadPool();
        CountDownLatch countDownLatch=new CountDownLatch(total);
        for (int i=0;i<total;i++){
            final int threadNum=i;
            executorService.execute(()-> {
                test(threadNum,countDownLatch.getCount());
                countDownLatch.countDown();
            });
        }

        countDownLatch.await();
        System.out.println("CountDownLatch --- finish:"+countDownLatch.getCount());

        executorService.shutdown();
    }

    private static void test(int time,long count){
        System.out.println(time+" --- "+count);
    }
}