@Test
	public void testSet() {
		ExecutorService threadPool = Executors.newSingleThreadExecutor();
		

		Set<String> _set = new HashSet<>();
		_set.add("1");
		_set.add("22");
		set = _set;
//		set = Collections.synchronizedSet(_set);
//		set = Collections.unmodifiableList(_set);
		
		threadPool.execute(new Runnable() {
			@Override
			public void run() {
				for (String string : set) {
					System.out.printf(string + " ");
					try {
						Thread.sleep(1000);
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}
				System.out.println();
			}
		});
		
		_set = new HashSet<>();
		_set.add("a");
		try {
			Thread.sleep(100);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		_set.add("bb");
		set = _set;
//		set = Collections.synchronizedSet(_set);
//		set = Collections.unmodifiableList(_set);
		
		threadPool.shutdown();
		try {
			Thread.sleep(3000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}