java实现异步转同步

来源：互联网发布：大数据架构详解编辑：程序博客网时间：2024/06/06 14:07

由于工作中会用到多个子线程需要同步的问题，所以了解到一个类：

CountDownLatch

这个类内部有计数器，当计数器为0时才会执行下一步操作。这个计数值就是你需要同步的步骤数，通过构造方法传入。

案例：

public class CountDownLatchDemo {
final static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
public static void main(String[] args) throws InterruptedException {
//实现两个工人工作，必须两个工作任务同时完成才能进行下一步。
//采用CountDownLatch类来实现
CountDownLatch latch = new CountDownLatch(2);// 计数器赋值为2
Worker worker1 = new Worker("杨杨", 5000, latch);
Worker worker2 = new Worker("黄黄", 8000, latch);
worker1.start();//开始工作
worker2.start();//开始工作
latch.await();//等待所有人完成工程
System.out.println("所有人工作已经完成");
}
static class Worker extends Thread{
private String workername;
private int worktime;
private CountDownLatch latch;
public void run(){
System.out.println("Worker:"+workername+" do work begin at "+sdf.format(new Date()));
doWork();
System.out.println("Worker:"+workername+" do work end at "+sdf.format(new Date()));
latch.countDown();//计数器减一
}
public Worker(String workername,int worktime,CountDownLatch latch){
this.workername = workername;
this.worktime = worktime;
this.latch = latch;
}
private void doWork(){
try{
Thread.sleep(worktime);
}catch(InterruptedException e){
e.printStackTrace();
}
}
}
}

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