I've written a lot of Clojure now, and I've managed to avoided learning any Java really.
What bits of java have you ended up needing? Like do you often use java libraries that don’t have clojure wrappers?
I feel like I’m often running up against little things. I’ll google “how to do xyz in clojure” and the top SO answer is to use a java library that apparently everybody already knows about, cause so many clojurists came from java first!
The same with Clojurescript and JS (and probably with Clojure-Dart) - you have nice interop with the hosting platform. The need for learning anything about Java (while writing Clojure) basically boils down to finding API documentation for a specific class and simply using it. That's all. That's all you'd ever need.