docs: public static String join ( CharSequence delimiter, CharSequence... elements ) {
          StringBuilder sb = new StringBuilder();
          for ( CharSequence element : elements ) {
              if ( sb.length() > 0 ) {
                  if ( delimiter != null ) {
                      sb.append(delimiter);
                  }
                  else {
                      sb.append("null");
                  }
              }
              sb.append(element);
          }
          return sb.toString();
      }