public boolean retainAll(LongIterable source)
{
int oldSize = this.size();
final LongSet sourceSet = source instanceof LongSet ? (LongSet) source : source.toSet();
LongLongHashMap retained = LongLongHashMap.this.select(new LongLongPredicate()
{
public boolean accept(long key, long value)
{
return sourceSet.contains(value);
}