code: public static String defaultIfBlank(String _str, String _default) {
          return isBlank(_str) ? _default : _str;
      }
docs: Checks if given String is blank (see {@link #isBlank(String)}.<br>
  If String is blank, the given default is returned, otherwise the String is returned.
  @param _str string to check
  @param _default default in case of blank string
  @return _str or _default