[orp]

You should take a look at scala's OpenHashMap - a mutable hashmap in the scala standard library that is often as fast as ju.HashMap. Link to scala doc: http://www.scala-lang.org/api/current/index.html#scala.colle...

[trailfox]

I have used OpenHashMap, but the results are mixed sometimes is much faster, other times it's much slower. It really depends on the use case.