It depends on the level of proficiency you want to gain in Clojure and Scala. At this point in time,to make the most of either language and to develop a "real"

It depends on the level of proficiency you want to gain in Clojure and Scala. At this point in time,to make the most of either language and to develop a "real" application you should know Java and not just Java but the tool, library and the infrastructure support of the Java ecosystem that comes with it. Having said that, if you just want to "learn" the language i.e. the Type System, really grok STM , the API's and how to do something in it - then there can be no better substitute than to start building the libraries,tools etc. that do not exist in Clojure and Scala. Pick up something that you currently can't do in Scala without dropping into Java and build it. Of course this is not an easy undertaking but you will learn lots.