线程：Semaphore实现信号灯

 1 package ch03;
 2 
 3 import java.util.concurrent.ExecutorService;
 4 import java.util.concurrent.Executors;
 5 import java.util.concurrent.Semaphore;
 6 
 7 public class SemaphoreTest {
 8 
 9     public static void main(String[] args) {
10         ExecutorService threadPool = Executors.newCachedThreadPool();
11         //获取三个许可的信号灯
12         final Semaphore sp = new Semaphore(5);
13         for(int i=1; i<=10; i++){
14             final int index = i;
15             Runnable runable = new Runnable() {
16                 
17                 @Override
18                 public void run() {
19                     try {
20                         //获取一个信号灯
21                         sp.acquire();
22                     } catch (InterruptedException e) {
23                         e.printStackTrace();
24                     }
25                     System.out.println("有一个"+Thread.currentThread().getName()+
26                             "线程进来了，当前有"+(5-sp.availablePermits())+"线程正在并发...");
27                     
28                     try {
29                         Thread.sleep(index * 1000);
30                     } catch (InterruptedException e) {
31                         e.printStackTrace();
32                     }
33                     //释放信号灯
34                     sp.release();
35                     System.out.println("线程"+Thread.currentThread().getName()+"离开了，现在还有"+(5-sp.availablePermits())+"个线程!");
36                 }
37             };
38             threadPool.execute(runable);
39         }
40         threadPool.shutdown();
41     }
42 
43 }