CountDownLatch 倒计时门栓用例

import java.util.concurrent.CountDownLatch;

class Driver { 
	   void main() throws InterruptedException {
	     CountDownLatch startSignal = new CountDownLatch(1);
	     CountDownLatch doneSignal = new CountDownLatch(5); //等待5个线程 doneSignal.countDown();

	     for (int i = 0; i < 5; ++i) 
	       new Thread(new Worker(startSignal, doneSignal)).start();

	     System.out.println("主线程控制Worker开始工作");          
	     startSignal.countDown();      
	     System.out.println("主线程工作"); 
	     System.out.println("主线程await等待worker完成任务");
	     doneSignal.await();           
	   }
	 }

	 class Worker implements Runnable {
	   private final CountDownLatch startSignal;
	   private final CountDownLatch doneSignal;
	   Worker(CountDownLatch startSignal, CountDownLatch doneSignal) {
	      this.startSignal = startSignal;
	      this.doneSignal = doneSignal;
	   }
	   public void run() {
	      try {
	    	System.out.println("Worker等待主线程发令");   
	        startSignal.await();
	        doWork();
	        System.out.println("Worker完成任务通知");  
	        doneSignal.countDown();
	} catch (InterruptedException ex) {} // return;
	   }

	   void doWork() { System.out.println("Worker开始工作");   }
	 }