code: static int parseInt(String key, @Nullable String value) {
      requireArgument((value != null) && !value.isEmpty(), "value of key %s was omitted", key);
      try {
        return Integer.parseInt(value);
      } catch (NumberFormatException e) {
        throw new IllegalArgumentException(String.format(
            "key %s value was set to %s, must be an integer", key, value), e);
      }
    }
docs: Returns a parsed int value.