Semaphore

Semaphore 通常用于限制可以访问某些资源的线程数目，demo：

package com.jerry.concurrency;

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

//排队上厕所
public class TestSemaphore {
	public static void main(String[] args) {
		 ExecutorService 人 =Executors.newCachedThreadPool();
		 final Semaphore 茅坑 =new Semaphore(2);
		     for(int i=0;i<10;i++){
		    	 人.submit(new Runnable(){
					@Override
					public void run() {
					try{
					               茅坑.acquire();
					     System.out.println("人["+Thread.currentThread().getName()+"]进入厕所，还有"+茅坑.availablePermits()+"个空坑"); 
					     System.out.println("人["+Thread.currentThread().getName()+"]获得坑位,开始大便...");
					     Thread.sleep((int)(Math.random()*1000));
						} catch(Exception e){
						  e.printStackTrace();
						}finally{  
					      System.out.println("人["+Thread.currentThread().getName()+"]使用完毕离开，当前还有"+(茅坑.availablePermits()+1)+"个空坑");
				                               茅坑.release();
						}
					}
				});
		     }
		     人.shutdown();
		     茅坑.acquireUninterruptibly(2);
		 System.out.println("使用完毕，阿姨需要清扫了卫生了！");
		     茅坑.release(2);
	}

}