findDuplicates method
Finds duplicates and then returns a Set with the duplicated elements. If there are no duplicates, an empty Set is returned.
Implementation
Set<T> findDuplicates() {
final Set<T> duplicates = <T>{};
final Set<T> auxSet = HashSet<T>();
for (final T element in this) {
if (!auxSet.add(element)) duplicates.add(element);
}
return duplicates;
}