简述
用来干嘛的?当你在方法中调用了多个线程,对数据库进行了一些不为人知的操作后,还有一个操作需要留到前者都执行完的重头戏,就需要用到 CountDownLatch
了
实践代码
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package com.github.gleans; import java.util.concurrent.CountDownLatch; public class TestCountDownLatch { public static void main(String[] args) throws InterruptedException { CountDownLatch latch = new CountDownLatch( 3 ); new KeyPass(1000L, "thin jack" , latch).start(); new KeyPass(2000L, "noral jack" , latch).start(); new KeyPass(3000L, "fat jack" , latch).start(); latch.await(); System.out.println( "此处对数据库进行最后的插入操作~" ); } static class KeyPass extends Thread { private long times; private CountDownLatch countDownLatch; public KeyPass( long times, String name, CountDownLatch countDownLatch) { super (name); this .times = times; this .countDownLatch = countDownLatch; } @Override public void run() { try { System.out.println( "操作人:" + Thread.currentThread().getName() + "对数据库进行插入,持续时间:" + this .times / 1000 + "秒" ); Thread.sleep(times); countDownLatch.countDown(); } catch (InterruptedException e) { e.printStackTrace(); } } } } |
图解
使用await()提前结束操作
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package com.github.gleans; import java.util.concurrent.CountDownLatch; import java.util.concurrent.TimeUnit; public class TestCountDownLatch { public static void main(String[] args) throws InterruptedException { CountDownLatch latch = new CountDownLatch( 3 ); new KeyPass(2000L, "公司一" , latch).start(); new KeyPass(3000L, "公司二" , latch).start(); new KeyPass(5000L, "公司三" , latch).start(); latch.await( 2 , TimeUnit.SECONDS); System.out.println( "~~~贾总PPT巡演~~~~" ); System.out.println( "~~~~融资完成,撒花~~~~" ); } static class KeyPass extends Thread { private long times; private CountDownLatch countDownLatch; public KeyPass( long times, String name, CountDownLatch countDownLatch) { super (name); this .times = times; this .countDownLatch = countDownLatch; } @Override public void run() { try { Thread.sleep(times); System.out.println( "负责人:" + Thread.currentThread().getName() + "开始工作,持续时间:" + this .times / 1000 + "秒" ); countDownLatch.countDown(); } catch (InterruptedException e) { e.printStackTrace(); } } } } |
假设公司一、公司二、公司三各需要2s、3s、5s来完成工作,贾总等不了,只能等2s,那么就设置await的超时时间
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latch.await( 2 , TimeUnit.SECONDS); |
执行结果
负责人:公司一开始工作,持续时间:2秒
~~~贾总PPT巡演~~~~
~~~~融资完成,撒花~~~~
负责人:公司二开始工作,持续时间:3秒
负责人:公司三开始工作,持续时间:5秒
方法描述
总结
这个操作可以说是简单好用
,目前还未遇见副作用
,若是有大佬,可以告知弟弟一下,提前表示感谢~
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原文链接:https://blog.csdn.net/Fine_Cui/article/details/107144502