Why not allow an external interface to provide hashCode/equals for a HashMap?

Question

With a TreeMap it\'s trivial to provide a custom Comparator, thus overriding the semantics provided by Comparable objects added to the

Answer 1

There's such a feature in com.google.common.collect.CustomConcurrentHashMap, unfortunately, there's currently no public way how to set the Equivalence (their Hasharator). Maybe they're not yet done with it, maybe they don't consider the feature to be useful enough. Ask at the guava mailing list.

I wonder why it haven't happened yet, as it was mentioned in this talk over two years ago.