class hello {
	public static void main(String[] args) throws ParseException {
		Scanner sc = new Scanner(System.in);
		String s = sc.nextLine();
		char[] c = s.toCharArray();
		TreeSet<Character>  ts = new TreeSet<>(new Comparator<Character>() {//匿名內部類定義Comparator
			@Override
			public int compare(Character c1, Character c2) {
				// TODO Auto-generated method stub
				int result = c1.charValue() - c2.charValue();
				return result == 0 ? 1 : result;
			}
		});
		
		for (Character d : c) {
			ts.add(d);
		}
		for (Character character : ts) {
			System.out.print(" "+character);
		}
	}
 

編譯結果: