code: private void resetFields() {
          until = null;
          freq = count = interval = bysecondCount = byminuteCount = byhourCount =
                  bydayCount = bymonthdayCount = byyeardayCount = byweeknoCount = bymonthCount =
                          bysetposCount = 0;
      }
docs: Resets parser-modified fields to their initial state.  Does not alter startDate.
  <p/>
  The original parser always set all of the "count" fields, "wkst", and "until",
  essentially allowing the same object to be used multiple times by calling parse().
  It's unclear whether this behavior was intentional.  For now, be paranoid and
  preserve the existing behavior by resetting the fields.
  <p/>
  We don't need to touch the integer arrays; they will either be ignored or
  overwritten.  The "startDate" field is not set by the parser, so we ignore it here.