docs: public static boolean isLetterOrNumeric(String str, int beginIndex, int endIndex)
      {
          for ( int i = beginIndex; i < endIndex; i++ ) {
              char chr = str.charAt(i);
              if ( ! StringUtil.isEnLetter(chr)
                      && ! StringUtil.isEnNumeric(chr) ) {
                  return false;
              }
          }
  
          return true;
      }