code: private static boolean isNumeric(String value) {
      for (char c : value.toCharArray()) {
        if (!Character.isDigit(c)) {
          return false;
        }
      }
      return true;
    }
docs: Returns a boolean indicating whether the given string value is numeric.
  
  @param value The value to check.
  @return Indicates whether the given string value is numeric.