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