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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

    例子如下:

    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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  • 原文地址:https://www.cnblogs.com/longshiyVip/p/5205750.html
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