public static synchronized void
setDefaultCache(Cache cache, int dclass) {
	DClass.check(dclass);
	defaultCaches.put(Mnemonic.toInteger(dclass), cache);
}
Sets the Cache to be used as the default for the specified class by future
Lookups.
@param cache The default cache for the specified class.
@param dclass The class whose cache is being set.
src/main/java/core/org/xbill/DNS/Lookup.java