public static boolean doubleLetters(String word) {

      char[] wordArr = word.toCharArray();

      for (int i = 0; i < word.length(); i++) {
          for (int j = i + 1; j < wordArr.length; j++) {
              if (word.charAt(i) == wordArr[j]) {
                  return true;
              }
          }
      }
      return false;
  }