package org.lkl.thead.foo;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Semaphore;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;/** *  * Function : 信号灯 * @author : Liaokailin * CreateDate : 2014-6-19 * version : 1.0 */public class SemaphoreFoo {        public static void main(String[] args) {        ExecutorService threadPool = Executors.newCachedThreadPool() ;        final Semaphore sp = new Semaphore(3) ; //3个信号等        for(int i= 1 ;i<=10 ;i++){            Runnable runnable = new Runnable() {                                @Override                public void run() {                                            //获取一个信号灯                        try {                            sp.acquire() ;                        } catch (InterruptedException e) {                            e.printStackTrace();                        }                                                System.out.println("线程:"+Thread.currentThread().getName()+                                " 获得信号灯 开始工作,当前并发的线程有:"+(3-sp.availablePermits()));                                                try {                            Thread.sleep((long)(Math.random()*10000)) ;//线程休眠 （模拟线程的业务执行）                        } catch (InterruptedException e) {                            e.printStackTrace();                        }                                                 System.out.println("线程:"+Thread.currentThread().getName()+"即将释放信号灯.");                            sp.release() ; //释放信号灯 此时其他线程就可以抢占释放的信号灯                                                        //下面代码有时候执行不准确，因为其没有和上面的代码合成原子单元                            System.out.println("线程" + Thread.currentThread().getName() +                                     "已离开，当前已有" + (3-sp.availablePermits()) + "个并发");                                        }            };                                    threadPool.execute(runnable) ; //线程启动.        }    }}