CountDownLatch使用

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