Java线程：新特征-信号量

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

/** 
* Java线程：新特征-信号量 
* 
* @author leizhimin 2009-11-5 13:44:45 
*/ 
public  class Test { 
         public  static  void main(String[] args) { 
                MyPool myPool =  new MyPool(20); 
                 //创建线程池 
                ExecutorService threadPool = Executors.newFixedThreadPool(2); 
                MyThread t1 =  new MyThread( "任务A", myPool, 3); 
                MyThread t2 =  new MyThread( "任务B", myPool, 12); 
                MyThread t3 =  new MyThread( "任务C", myPool, 7); 
                 //在线程池中执行任务 
                threadPool.execute(t1); 
                threadPool.execute(t2); 
                threadPool.execute(t3); 
                 //关闭池 
                threadPool.shutdown(); 
        } 
} 

/** 
* 一个池 
*/ 
class MyPool { 
         private Semaphore sp;      //池相关的信号量 

         /** 
         * 池的大小，这个大小会传递给信号量 
         * 
         * @param size 池的大小 
         */ 
        MyPool( int size) { 
                 this.sp =  new Semaphore(size); 
        } 

         public Semaphore getSp() { 
                 return sp; 
        } 

         public  void setSp(Semaphore sp) { 
                 this.sp = sp; 
        } 
} 

class MyThread  extends Thread { 
         private String threadname;             //线程的名称 
         private MyPool pool;                         //自定义池 
         private  int x;                                     //申请信号量的大小 

        MyThread(String threadname, MyPool pool,  int x) { 
                 this.threadname = threadname; 
                 this.pool = pool; 
                 this.x = x; 
        } 

         public  void run() { 
                 try { 
                         //从此信号量获取给定数目的许可 
                        pool.getSp().acquire(x); 
                         //todo：也许这里可以做更复杂的业务 
                        System.out.println(threadname +  "成功获取了" + x +  "个许可！"); 
                }  catch (InterruptedException e) { 
                        e.printStackTrace(); 
                }  finally { 
                         //释放给定数目的许可，将其返回到信号量。 
                        pool.getSp().release(x); 
                        System.out.println(threadname +  "释放了" + x +  "个许可！"); 
                } 
        } 
}