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
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