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

I'd say in most cases you can rely on efficient implementations of hashCode(). AFAIK, that method is only invoked on lookup methods (like contains, get etc.) or methods that change the collection (add/put, remove etc.).

Thus, in most cases there shouldn't be any need to cache hashes yourself.