public static Set<Integer> find_stop_words_position(List<String> vocabulary, List<String> stopword) {
		Set<Integer> stop_word_position = new HashSet<Integer>();
		for (int i = 0; i < vocabulary.size(); i++) {
			for (int j = 0; j < stopword.size(); j++) {
				if (vocabulary.get(i).toString().equals(stopword.get(j).toString())) {
					stop_word_position.add((i+1));
				}
			}
		}

		return stop_word_position;
	}