There's a few threads on SO that try to summarize what you need to know if you haven't programmed in java before(and, yes, it's a decent amount), e.g. what a JAR is, classpath, -server vs. -client, -Xmx and Xms, GC options etc. Alternatively, ask on reddit, IRC or the mailing list

http://stackoverflow.com/questions/5721496/learning-java-so-...

http://stackoverflow.com/questions/11358929/what-should-a-sc...

http://www.reddit.com/r/Clojure/comments/1ev4u5/what_do_i_ne...