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.wait(); //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
}
}
}