CountDownLatch使用场景

深碍√TFBOYSˉ_ 2022-06-12 22:24 199阅读 0赞

使用场景：主线程在执行完一系列业务后才会执行最后的操作。

1、学生体能测试，需要全部测试完成后再去处理体能的排名情况。

现有5名学生：

public class BodyTest {
    	public static void main(String[] args) {
    		CountDownLatch latch = new CountDownLatch(5);
    		for (int i = 1; i < 6; i++) {
    			new Thread(() -> {
    				System.out.println("学生" + Thread.currentThread().getName() + "开始测试");
    				try {
    					TimeUnit.SECONDS.sleep(1);
    				} catch (InterruptedException e) {
    					e.printStackTrace();
    				}
    				System.out.println("学生" + Thread.currentThread().getName() + "测试完毕");
    				latch.countDown();
    			}, i + "").start();
    		}
    		try {
    			latch.await();
    		} catch (InterruptedException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    		System.out.println("5个学生测试完毕！开始处理结果。。");
    	}
    }

2、开启两个线程，5s后结束线程2

public class T44Latch {
    	static int count;
    	static CountDownLatch latch = new CountDownLatch(1);
    
    	public static void main(String[] args) {
    		new Thread(() -> {
    			System.out.println(Thread.currentThread().getName() + " start..");
    			if (count != 5) {
    				try {
    					latch.await();
    				} catch (Exception e) {
    					// TODO Auto-generated catch block
    					e.printStackTrace();
    				}
    			}
    			System.out.println(Thread.currentThread().getName() + " end..");
    		}, "t1").start();
    		new Thread(() -> {
    			for (int i = 0; i < 10; i++) {
    				count++;
    				System.out.println(i);
    				if (count == 5) {
    					latch.countDown();
    				}
    				try {
    					TimeUnit.SECONDS.sleep(1);
    				} catch (Exception e) {
    					// TODO Auto-generated catch block
    					e.printStackTrace();
    				}
    			}
    		}, "t2").start();
    	}
    }