Caching hashes in Java collections?

Question

When I implement a collection that uses hashes for optimizing access, should I cache the hash values or assume an efficient implementation of hashCode()?

On

Answer 1

Considering that java.lang.String caches its hash, i guess that hashcode() is supposed to be fast.

So as first approach, I would not cache hashes in my collection. In my objects that I use, I would not cache hash code unless it is oviously slow, and only do it if profiling tell me so.

If my objects will be used by others, i would probubly consider cachnig hash codes sooner (but needs measurements anyway).