Java collections — polymorphic access to elements

Question

I have a LinkedHashSet of values of ThisType. ThisType is implementing the interface ThatType.

I ne

Answer 1

I think what you want is to use wildcards.

 LinkedHashSet someFunction(LinkedHashSet set) {
      return set;
 }

As has been explained elsewhere LinkedHashSet is not a subclass of LinkedHashSet, since LinkedHashSet can't accept ThatType objects.

The wildcard in LinkedHashSet means a LinkedHastSet of some class (not sure what) that extends ThatType.

Though you may want to consider using this:

 Set someFunction(Set set) {
      return set;
 }