Java中CountDownLatch用法解析

 import java.util.concurrent.CountDownLatch; import java.util.concurrent.Executor; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors;  public class CountDownLatchDemo {   private static final int PLAYER_AMOUNT = 5;   public CountDownLatchDemo() {     // TODO Auto-generated constructor stub     }   /**   * @param args   */   public static void main(String[] args) {     // TODO Auto-generated method stub     //对于每位运动员，CountDownLatch减1后即结束比赛     CountDownLatch begin = new CountDownLatch(1);     //对于整个比赛，所有运动员结束后才算结束     CountDownLatch end = new CountDownLatch(PLAYER_AMOUNT);     Player[] plays = new Player[PLAYER_AMOUNT];          for(int i=0;i<PLAYER_AMOUNT;i++)       plays[i] = new Player(i+1,begin,end);          //设置特定的线程池，大小为5     ExecutorService exe = Executors.newFixedThreadPool(PLAYER_AMOUNT);     for(Player p:plays)       exe.execute(p);      //分配线程     System.out.println("Race begins!");     begin.countDown();     try{       end.await();      //等待end状态变为0，即为比赛结束     }catch (InterruptedException e) {       // TODO: handle exception       e.printStackTrace();     }finally{       System.out.println("Race ends!");     }     exe.shutdown();   } }

import java.util.concurrent.CountDownLatch;   public class Player implements Runnable {    private int id;   private CountDownLatch begin;   private CountDownLatch end;   public Player(int i, CountDownLatch begin, CountDownLatch end) {     // TODO Auto-generated constructor stub     super();     this.id = i;     this.begin = begin;     this.end = end;   }    @Override   public void run() {     // TODO Auto-generated method stub     try{       begin.await();    //等待begin的状态为0       Thread.sleep((long)(Math.random()*100));  //随机分配时间，即运动员完成时间       System.out.println("Play"+id+" arrived.");     }catch (InterruptedException e) {       // TODO: handle exception       e.printStackTrace();     }finally{       end.countDown();  //使end状态减1，最终减至0     }   } }