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Java多线程CountDownLatch用法


 

 
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
 
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();
            }
        }
    }
 
 
}