/**
* 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！");
                }
        }
}