Can an object that instantiates the HashSet class contain multiple copies of some element? Suppose you want to define a class that orders its elements like a List but does not allow multiple...

Can an object that instantiates the HashSet class contain multiple copies of

some element?

Suppose you want to define a class that orders its elements like a List but does not allow multiple occurrences of an element like a Set. Would it be better to make it a derived class of the ArrayList class or a derived class of the HashSet class?