I gained most of my expertise about the JVM running Ruby apps on it with JRuby (and after that, Clojure). I started out something of a Java-hater and eventually

I gained most of my expertise about the JVM running Ruby apps on it with JRuby (and after that, Clojure). I started out something of a Java-hater and eventually came around to kind of sort of liking Java (although I'd certainly rather write Ruby in the overwhelming majority of cases)