public static String firstNonRepeatedCharacter(String str) {
  Map<Integer, Long> chs = str.codePoints()
    .mapToObj(cp -> cp)
    .collect(Collectors.groupingBy(Function.identity(),
      LinkedHashMap::new, Collectors.counting()));

  int cp = chs.entrySet().stream()
    .filter(e -> e.getValue() == 1L)
    .findFirst()
    .map(Map.Entry::getKey)
    .orElse(Integer.valueOf(Character.MIN_VALUE));

  return String.valueOf(Character.toChars(cp));
}