public static void readFile(Map<Integer, UserPreferences> mapUP ,Map<Integer, ItemPreferences> mapIT ) throws FileNotFoundException{
		File file  = new File("u.data");
		Scanner sc = new Scanner(file);
		while(sc.hasNextLine()){
			StringTokenizer st = new StringTokenizer(sc.nextLine(), "\t");
			int userId = Integer.parseInt(st.nextToken());
			int itemId = Integer.parseInt(st.nextToken());
			double rating = Double.parseDouble(st.nextToken());
			UserPreferences up = mapUP.get(userId);
			ItemPreferences it = mapIT.get(itemId);
			if(up == null){
				up = new UserPreferences(userId);
				mapUP.put(userId, up);
			}if(it == null){
				it = new ItemPreferences(itemId);
				mapIT.put(itemId, it);
			}
			up.setElement(itemId, rating);
			it.setElement(userId, rating);
		}
	}