public void run() {
			while(! isInterrupted()) {  //isInterrupted()̳Thread࣬ж߳Ƿж
				Runnable task = null;
				try {
					task = getTask(id);		//ȡ
				}catch(InterruptedException ex) {
					ex.printStackTrace();
				}
				//getTask()nullִ߳getTask()ʱжϣ߳
				if(task == null) return;
				
				try {
					task.run();  //
				}catch(Throwable t) {
					t.printStackTrace();
				}
			}//  end while
		}//  end run