docs: public DateTimeFormatter getFormatter() {
          DateTimeFormatter[] f = iFormatter;
          if (f == null) {
              if (size() == 0) {
                  return null;
              }
              f = new DateTimeFormatter[2];
              try {
                  List<DateTimeFieldType> list = new ArrayList<DateTimeFieldType>(Arrays.asList(iTypes));
                  f[0] = ISODateTimeFormat.forFields(list, true, false);
                  if (list.size() == 0) {
                      f[1] = f[0];
                  }
              } catch (IllegalArgumentException ex) {
                  // ignore
              }
              iFormatter = f;
          }
          return f[0];
      }