[lunch]

I'd recommend learning a few, here's my 2 cents:

- Start with Python, it's a very common dynamic language in the wild.

- From Python it's easy to learn Go and you'll want some Go experience if you want to work on distributed systems in today's culture.

- Javascript is another extremely useful one to know that you'll find everywhere, start with the book "Javascript the good parts".

Adding these in addition to your Java base would make you very well rounded, IMO.

In my 5-6 years of professional experience (startups and enterprise, full stack to infrastructure) I've never encountered Kotlin/Elixir/Haskell/Swift.

[amorphid]

If you learned Elixir, it would not surprise me if you started to prefer Elixir for most backend projects.