private void
safeAddRR(Record r) {
	if (!(r instanceof RRSIGRecord)) {
		if (nsigs == 0)
			rrs.add(r);
		else
			rrs.add(rrs.size() - nsigs, r);
	} else {
		rrs.add(r);
		nsigs++;
	}
}
Creates an RRset with the contents of an existing RRset
src/main/java/core/org/xbill/DNS/RRset.java