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CountDownLatch,一个同步辅助类,在完成一组正在其他线程中执行的操作之前,它允许一个或多个线程一直等待

2016-04-30 21:20 615 查看
CountDownLatch,一个同步辅助类,在完成一组正在其他线程中执行的操作之前,它允许一个或多个线程一直等待。

主要方法

public CountDownLatch(int count);

public void countDown();

public void await() throws InterruptedException

构造方法参数指定了计数的次数

countDown方法,当前线程调用此方法,则计数减一

awaint方法,调用此方法会一直阻塞当前线程,直到计时器的值为0

例子

Java代码


public class CountDownLatchDemo {

final static SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

public static void main(String[] args) throws InterruptedException {

CountDownLatch latch=new CountDownLatch(2);//两个工人的协作

Worker worker1=new Worker("zhang san", 5000, latch);

Worker worker2=new Worker("li si", 8000, latch);

worker1.start();//

worker2.start();//

latch.await();//等待所有工人完成工作

System.out.println("all work done at "+sdf.format(new Date()));

}

static class Worker extends Thread{

String workerName;

int workTime;

CountDownLatch latch;

public Worker(String workerName ,int workTime ,CountDownLatch latch){

this.workerName=workerName;

this.workTime=workTime;

this.latch=latch;

}

public void run(){

System.out.println("Worker "+workerName+" do work begin at "+sdf.format(new Date()));

doWork();//工作了

System.out.println("Worker "+workerName+" do work complete at "+sdf.format(new Date()));

latch.countDown();//工人完成工作,计数器减一

}

private void doWork(){

try {

Thread.sleep(workTime);

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

}

输出:

Worker zhang san do work begin at 2011-04-14 11:05:11

Worker li si do work begin at 2011-04-14 11:05:11

Worker zhang san do work complete at 2011-04-14 11:05:16

Worker li si do work complete at 2011-04-14 11:05:19

all work done at 2011-04-14 11:05:19
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