public boolean
isCurrent() {
	BasicHandler handler = getBasicHandler();
	return (handler.axfr == null && handler.ixfr == null);
}
Returns true if the response indicates that the zone is up to date.
This will be true only if an IXFR was performed.
@throws IllegalArgumentException The transfer used the callback interface,
so the response was not stored.
src/main/java/core/org/xbill/DNS/ZoneTransferIn.java