private static ThreadPoolExecutor getPool() {
		if (POOL == null)
			synchronized (ThreadPoolExecutor.class) {
				if (POOL == null) {
					int MaxPoolMultiple = POOL_MULTIPLE * (AVAILABLE_PROCESSPRS <= 0 ? 1 : AVAILABLE_PROCESSPRS);
					if (QUEUE == null) // jetty的线程池队列也是BlockingQueue，参考一下
						QUEUE = new ArrayBlockingQueue<Runnable>(MaxPoolMultiple);
					if (REJECT_POLICY == null)
						REJECT_POLICY = new ThreadPoolExecutor.AbortPolicy();
					POOL = newPool(POOL_MULTIPLE, MaxPoolMultiple, KEEP_ALIVE, QUEUE, REJECT_POLICY);
					// .DiscardPolicy().DiscardOldestPolicy()抛弃旧的任务
				}
			}
		return POOL;
	}