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