public static void main(String[] args) {
        SelectApp app = new SelectApp();
        app.process();
    }

    private void process() {
        int[] input = {1, 2, 5, 1, 2, 4, 1, 2, 3, 3};
        Set<Integer> element = elementWithoutDuplicate(input);
        System.out.println("element: " + element);
    }

    private Set<Integer> elementWithoutDuplicate(int[] input) {
        List<Integer> coll = Arrays.stream(input).boxed().collect(Collectors.toList());
        Map<Integer, Long> map = coll.stream().collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
        return map.entrySet().stream().filter(entry -> entry.getValue() == 1).map(Map.Entry::getKey).collect(Collectors.toSet());
    }