When to use Enum or Collection in Java

Question

Under what circumstances is an enum more appropriate than, for example, a Collection that guarantees unique elements (an implementer of java.util.Set, I guess...)?

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Answer 1

In some situations your business requires the creation of new items, but at the same time business logic based on some fixed items. For the fixed ones you want an enum, the new ones obviously require some kind of collection/db.

I've seen projects using a collection for this kind of items, resulting in business logic depending on data which can be deleted by the user. Never do this, but do create a separate enum for the fixed ones and a collection for the others, just as required.

An other solution is to use a collection with immutable objects for the fixed values. These items could also reside in a db, but have an extra flag so users cannot update / delete it.