> Will there be efficiency differences large enough to warrant two different
> implementations
Taking a quick look at the current implementation, it seems that all the
methods that are being used are simply methods of Collection, so I don't see
any issues there. I guess we'll have to settle on some type of Collection
to return though. (Set?).
I guess I'll go ahead and introduce CollectionUtil, taking Collection
arguments, and I'll add disjunction() as alias for a deprecated sum().
I think we probably still want to think about the semantics of element
cardinality a bit--e.g., currently if list A has 1 copies of "foo", and list
B has 3 copies of "foo", ListUtils.itersection(A,B) will contain 3 copies,
which doesn't seem quite right to me. At that time "there be efficiency
differences large enough to warrant two different implementations". Let me
take a stab at it and I'll see what everyone thinks.
