多线程之赛跑-CountDownLatch

CountDownLatch

等所有的线程准备好之后发起执行后续流程.

 

代码如下：

/**
 * @author jeremy.li
 * @date 2020/11/30
 * @description
 */
public class CountDownLatchTest implements Runnable {

    static CountDownLatch countDownLatch = new CountDownLatch(5);


    @Override
    public void run() {
        try {
            Thread.sleep(new Random().nextInt(9)*1000);
            System.out.println(Thread.currentThread().getName() + ",已准备就绪");
            countDownLatch.countDown();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }

    public static void main(String[] args) throws InterruptedException {
        for (int i = 1; i < 6; i++) {
            CountDownLatchTest countDownLatchTest = new CountDownLatchTest();
            Thread thread = new Thread(countDownLatchTest, i + " 号运动员");
            thread.start();
        }
        countDownLatch.await();
        System.out.println("----开跑----");
    }
}

　　

 

关键方法：

await();

　　阻塞当前线程

countDown();

　　计数器-1，

描述：

　　await方法在主线程中执行，阻塞主线程，countDown在子线程中执行，将创建CountDownLatch时初始化计数器-1，当计数器=0时。主线程阻塞取消。