Java, Spring, SQL, XML processing, and recently Scala and NoSQL (E.g. Mongo) are good choices to invest in learning - they are used extensively but of course no

Java, Spring, SQL, XML processing, and recently Scala and NoSQL (E.g. Mongo) are good choices to invest in learning - they are used extensively but of course not exclusively. Don't worry about super special libraries - just cover the basics of some of the above and build something that "works" and it'll be good groundwork. What "Works" means is up for grabs, but any set of functions that expose you to the platforms will be worthwhile. All the concepts and capabilities you build in will do you personally a lot of good, and give you good talking points, but don't expect interviewing panels to be actually that picky about specifics - they want to find good developers, not bring in a 3rd party trading bot :-)