code: public static OptionalInt createInteger(final String str) {
          if (N.isNullOrEmpty(str)) {
              return OptionalInt.empty();
          }
  
          try {
              return OptionalInt.of(Integer.decode(str));
          } catch (NumberFormatException e) {
              return OptionalInt.empty();
          }
      }
docs: <p>
  Convert a <code>String</code> to a <code>Integer</code>, handling hex
  (0xhhhh) and octal (0dddd) notations. N.B. a leading zero means octal;
  spaces are not trimmed.
  </p>
  
  <p>
  Returns an empty {@code OptionalInt} if the string is {@code null} or can't be parsed as {@code Integer}.
  </p>
  
  @param str a <code>String</code> to convert, may be null
  @return