主线程等待子线程执行完毕后再执行

1. //Main主线程  
2. public class MainThread {   
3.    
4.     public static void main(String[] args) throws InterruptedException {   
5.         longstartTime = System.currentTimeMillis();   
6.         intthreadNum = 5;//线程数  
7.         //定义正在运行的线程数  
8.         CountDownLatch runningThreadNum = new CountDownLatch(threadNum);  
9.         System.out.println(Thread.currentThread().getName()+"-start");  
10.         //创建多个子线程  
11.         for(inti = 0; i < threadNum; i++) {   
12.             new SubThread(runningThreadNum).start();  
13.         }  
14.         //等待子线程都执行完了再执行主线程剩下的动作  
15.         runningThreadNum.await();  
16.         System.out.println(Thread.currentThread().getName()+"-end");  
17.         longendTime = System.currentTimeMillis();   
18.         System.out.println("runningTime:"+(endTime-startTime));  
19.     }  
20. }  

1. //子线程  
2. public class SubThread extends Thread{  
3.    
4.     //子线程记数器,记载着运行的线程数  
5.     private CountDownLatch runningThreadNum;   
6.    
7.     public SubThread(CountDownLatch runningThreadNum){   
8.         this.runningThreadNum = runningThreadNum;   
9.     }  
10.        
11.     @Override  
12.     public void run() {   
13.         System.out.println(Thread.currentThread().getName()+"-start");  
14.         System.out.println(Thread.currentThread().getName()+"-do something");  
15.         System.out.println(Thread.currentThread().getName()+"-end");  
16.         runningThreadNum.countDown();//正在运行的线程数减一  
17.     }  
18. }