java 多线程 CountDownLatch用法

转载自:http://www.iteye.com/topic/1002652

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  

1. public class CountDownLatchDemo {   
2.     final static SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");   
3.     public static void main(String[] args) throws InterruptedException {   
4.         CountDownLatch latch=new CountDownLatch(2);//两个工人的协作  
5.         Worker worker1=new Worker("zhang san", 5000, latch);   
6.         Worker worker2=new Worker("li si", 8000, latch);   
7.         worker1.start();//   
8.         worker2.start();//   
9.         latch.await();//等待所有工人完成工作   
10.         System.out.println("all work done at "+sdf.format(new Date()));   
11.     }   
12.        
13.        
14.     static class Worker extends Thread{   
15.         String workerName;    
16.         int workTime;   
17.         CountDownLatch latch;   
18.         public Worker(String workerName ,int workTime ,CountDownLatch latch){   
19.              this.workerName=workerName;   
20.              this.workTime=workTime;   
21.              this.latch=latch;   
22.         }   
23.         public void run(){   
24.             System.out.println("Worker "+workerName+" do work begin at "+sdf.format(new Date()));   
25.             doWork();//工作了   
26.             System.out.println("Worker "+workerName+" do work complete at "+sdf.format(new Date()));   
27.             latch.countDown();//工人完成工作，计数器减一  
28.   
29.         }   
30.            
31.         private void doWork(){   
32.             try {   
33.                 Thread.sleep(workTime);   
34.             } catch (InterruptedException e) {   
35.                 e.printStackTrace();   
36.             }   
37.         }   
38.     }   
39.        
40.         
41. }  

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