并法包信号量的使用

https://www.cnblogs.com/amosli/p/3687776.html

/** 
* @ClassName: SemaPhoreTest 
* @Description: 线程通信中的"信号灯"
* @author: amosli
* @email:hi_amos@outlook.com
* @date Apr 25, 2014 12:06:22 AM  
*/
public class SemaPhoreTest {
    public static void main(String[] args) {
        ExecutorService threadPool = Executors.newCachedThreadPool();
        
        final Semaphore semaphore=new Semaphore(3);
        for(int i=0;i<10;i++){
            threadPool.execute(new Runnable() {
                public void run() {
                    try {
                        semaphore.acquire();//获取一个可用的permits
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    System.out.println("线程 " + Thread.currentThread().getName()+" 已进入.  " + "目前已经有"+(3-semaphore.availablePermits())+" 个线程进入");
                    try {
                        Thread.sleep(new Random().nextInt(1000));
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("线程 "+Thread.currentThread().getName()+ " 即将离开...");
                    semaphore.release();//释放一个线程
                    System.out.println("线程 "+Thread.currentThread().getName()+ " 已离开.  当前有"+(3-semaphore.availablePermits())+"并发");
                }
            });
        }
    }
}