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