83-java-countDownLatch

本文架构

countDownLatch

1.作用
这是用来做多线程操作的类,和join方法类似
2.构造方法

• CountDownLatch countDownLatch = new CountDownLatch(1);
  #这个表示构造一个值为1的对象,当对象的值为0时,阻塞的方法则可继续执行

3.阻塞当前线程:

• countDownLatch.await();
  #这个方法表示阻塞当前线程,当本对象的值为0时,接着继续执行后面的代码

4.将对象的值减1:

• countDownLatch.countDown();
  #如果本对象的值原本就是1,执行本方法之后,则对象的值变为0,则本对象await()方法阻塞的线程将继续执行

public class TestCountDownLatch {
    //创建一个countDownLatch对象,并将初始值设置为3
    private static CountDownLatch countDownLatch = new CountDownLatch(3);

    public static void main(String[] args) throws Exception {
        for(int i = 0; i < 3; i ++) {
            Thread thread = new Thread() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(3000);
                        System.out.println("工作线程执行了");
                        System.out.println("工作线程将countDownLatch值减1");
                        //将countDownLatch值减1
                        countDownLatch.countDown();
                        System.out.println("当前countDownLatch的值:" + countDownLatch.getCount());
                    }catch (Exception e){
                        e.printStackTrace();
                    }

                }
            };
            thread.start();
        }
        //是主线程等待
        countDownLatch.await();
        System.out.println("我是主线程");
    }
}