Java骚操作之CountDownLatch代码详解

时间:2021-08-10 17:07:23

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

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

Java骚操作之CountDownLatch代码详解

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

Java骚操作之CountDownLatch代码详解

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