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