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
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();
}
}
}
}
使用await()提前结束操作
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
latch.await(2, TimeUnit.SECONDS);
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
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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