High-performance Concurrent MultiMap Java/Scala

Question

I am looking for a high-performance, concurrent, MultiMap. I have searched everywhere but I simply cannot find a solution that uses the same approach as ConcurrentHashMap (O

Answer 1

I am a bit late on this topic but I think, nowadays, you can use Guava like this:

Multimaps.newSetMultimap(new ConcurrentHashMap<>(), ConcurrentHashMap::newKeySet)