Find Duplicate Objects Generic Java Collection

Duplicates.java

public  <T> List<T> getDuplicate(Collection<T> list) {
	final List<T> duplicatedObjects = new ArrayList<T>();
	Set<T> set = new HashSet<T>() {
		@Override
		public boolean add(T e) {
			if (contains(e)) {
				duplicatedObjects.add(e);
			}
			return super.add(e);
		}
	};
	for (T t : list) {
		set.add(t);
	}
	return duplicatedObjects;
}