一直被忽略的java 多线程并发工具类 CountDownLatch、Semaphore

package com.test;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

public class Question2 implements Runnable{
private String name;
private Semaphore sem;
private CountDownLatch downLatch;

public Question2(String name, Semaphore sem,CountDownLatch downLatch) {
super();
this.name = name;
this.sem = sem;
this.downLatch = downLatch;
}

public void test(String name){
System.out.println(name + " in!");
try {
Thread.sleep(2 * 1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(name + " out!");
}

public static void main(String[] args) throws InterruptedException {
// TODO Auto-generated method stub
int thread_num = 10;
ExecutorService executorService = Executors.newCachedThreadPool();
Semaphore sem = new Semaphore(1); //每次产生信号量个数
CountDownLatch downLatch = new CountDownLatch(5); //初始化同步器

for(int i=0; i< thread_num;i++){
executorService.execute(new Question2("test "+i, sem,downLatch));
}
downLatch.await();
executorService.shutdown();
}

@Override
public void run() {
// TODO Auto-generated method stub
try {
sem.acquire();
this.test(this.name);
sem.release();
downLatch.countDown();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}