Java HashSet vs Array Performance

Question

I have a collection of objects that are guaranteed to be distinct (in particular, indexed by a unique integer ID). I also know exactly how many of them there are (and the n

Answer 1

theoretically, and as SCJP6 Study guide says :D

arrays are faster than collections, and as said, most of the collections depend mainly on arrays (Maps are not considered Collection, but they are included in the Collections framework)

if you guarantee that the size of your elements wont change, why get stuck in Objects built on Objects (Collections built on Arrays) while you can use the root objects directly (arrays)