CountDownLatch 用法

本是古典何须时尚 2022-08-10 09:25 183阅读 0赞

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][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 [ ![复制代码][icon_copy.gif]][_icon_copy.gif]  ![收藏代码][icon_star.png]![spinner.gif][]

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

[InterruptedException]: http://www.iteye.com/java/lang/InterruptedException.html
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