public static void main(String[] args) throws InterruptedException {
		int threadNum = 100;
		CountDownLatch threadSignal = new CountDownLatch(threadNum);
		for (int i = 0; i < threadNum; i++) {
			Thread t = new Thread(new SetUpdate(threadSignal));
			t.start();
		}
		new Thread(new Runnable() {

			@Override
			public void run() {
				if (!set.isEmpty()) {
					synchronized (set) {
						Iterator<Integer> iter = set.iterator();
						while (iter.hasNext()) {
							iter.remove();
						}
					}
				}

			}
		}).start();
		threadSignal.await();
		System.out.println(set);
	}