docs: public static boolean isEmpty(final CharSequence str) {
          if ( str == null || str.length() == 0 ) {
              return true;
          }
          
          for ( int i = 0, length = str.length(); i < length; i++ ){
              if ( !isWhitespace(str.charAt( i )) )  {
                  return false;
              }
          }
          
          return true;
      }