public void waitFinish() {
		synchronized (this) {
			isClosed = true;
			notifyAll();			//лgetTask()еȴĹ߳
		}
		Thread[] threads = new Thread[activeCount()]; //activeCount() ظ߳л̵߳Ĺֵ
		int count = enumerate(threads); //enumerate()̳ThreadGroup࣬ݻ̵߳Ĺֵ߳еǰлĹ߳
		for(int i =0; i < count; i++) { //ȴй߳̽
			try {
				threads[i].join();	//ȴ߳̽
			}catch(InterruptedException ex) {
				ex.printStackTrace();
			}
		}
	}