public void
setCache(Cache cache) {
	if (cache == null) {
		this.cache = new Cache(dclass);
		this.temporary_cache = true;
	} else {
		this.cache = cache;
		this.temporary_cache = false;
	}
}
Sets the cache to use when performing this lookup.  This overrides the
default value.  If the results of this lookup should not be permanently
cached, null can be provided here.
@param cache The cache to use.
src/main/java/core/org/xbill/DNS/Lookup.java