Earlier that may have been a worry, but I think it's pretty clear by now that's it's only helped. It's entirely possible to write comprehensive, complicated, programs in Clojure, using no Java. There are, too, many Clojure libs that either wrap Java or forgo it entirely in replacing Java. Java is really used to as a syscal language, and as Clojure runs on the JVM, that makes sense (no thank you, JVM bytecode).