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     //對(duì)于每位運(yùn)動(dòng)員，CountDownLatch減1后即結(jié)束比賽     CountDownLatch begin = new CountDownLatch(1);     //對(duì)于整個(gè)比賽，所有運(yùn)動(dòng)員結(jié)束后才算結(jié)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);          //設(shè)置特定的線程池，大小為5     ExecutorService exe = Executors.newFixedThreadPool(PLAYER_AMOUNT);     for(Player p:plays)       exe.execute(p);      //分配線程     System.out.println("Race begins!");     begin.countDown();     try{       end.await();      //等待end狀態(tài)變?yōu)?，即為比賽結(jié)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的狀態(tài)為0       Thread.sleep((long)(Math.random()*100));  //隨機(jī)分配時(shí)間，即運(yùn)動(dòng)員完成時(shí)間       System.out.println("Play"+id+" arrived.");     }catch (InterruptedException e) {       // TODO: handle exception       e.printStackTrace();     }finally{       end.countDown();  //使end狀態(tài)減1，最終減至0     }   } }