public boolean retainAll(DoubleIterable source)
{
int oldSize = this.size();
final DoubleSet sourceSet = source instanceof DoubleSet ? (DoubleSet) source : source.toSet();
LongDoubleHashMap retained = LongDoubleHashMap.this.select(new LongDoublePredicate()
{
public boolean accept(long key, double value)
{
return sourceSet.contains(value);
}