I'm from the RDMS school of thought and am wondering... in what cases does it make most sense to use a Set and when does it make most sense to use a List?

Are there any general rules of thumb? Can I get away with always using Sets for collections (i.e. what I think of as N-to-many relationships)

I almost always use Sets instead of lists. Lists have two attributes that make them unappealing to me: the listed entities have to have an entire column just for the list index value; and when you get a List instance, the elements are not ordered continuously in the list but are ordered by the index column with null values in the in between spaces.

Between Set and SortedSet I've been able to handle just about any entity model.

bags, on the other had, are great - and don't require messing with equals()/hashCode()

Could you elaborate?

In what cases would you use Set over Bag and vice versa. Are there instances where List is better than the other two?

Thanks.