code: public boolean isNumeral(final String input) {
          for (int i = 0; i < input.length(); i++) {
              if (!isNumeral(input.charAt(i))) {
                  return false;
              }
          }
          return true;
      }
docs: Numeral predicate
  
  @param input string to test
  @return true if and only if input is a numeral