My rule of thumb is, if you need to switch a primary production language more than once a decade[1], then you're picking them wrong.

Personally, I've been using Java for over a decade, and a few years ago I added Clojure to the mix and expect it to serve me for over a decade, as well. I like them both and believe they both qualify as good picks. I'm also adding Kotlin now, too, mostly because its switching cost and added risk are practically zero.

[1]: for reasons other than targeting a new platform