If you know Java then you can start by writing very Java-like code using the same libraries you would in Java - there are a lot of intimidating functional techniques available but you don't have to use them from day 1 (indeed I'd say you probably shouldn't use them until you understand why you would want to). IMO you're much better off picking a small corner of a JVM project (e.g. maybe a migration tool or a couple of tests) and using a little Scala in practice, rather than trying to learn it all to start with.