code: public List
  run() throws IOException, ZoneTransferException {
  	BasicHandler handler = new BasicHandler();
  	run(handler);
  	if (handler.axfr != null)
  		return handler.axfr;
  	return handler.ixfr;
  }
docs: Does the zone transfer.
  @return A list, which is either an AXFR-style response (List of Records),
  and IXFR-style response (List of Deltas), or null, which indicates that
  an IXFR was performed and the zone is up to date.
  @throws IOException The zone transfer failed to due an IO problem.
  @throws ZoneTransferException The zone transfer failed to due a problem
  with the zone transfer itself.