I'm not sure Java is worth the effort at this point. If I'm going to have to keep updating every 6 months, I would rather use Go, which seems to have all that Java has to offer + the backing of a huge corporation.
Personally, I wish Swift had a larger server-side ecosystem around it. I love the language, and some of the new web app frameworks (Vapor, Perfect, Kitura, etc.) are really great. However, there just aren't as many open-source, third-party libraries as there are for Java. To me, that's really Java's strength. There are libraries or clients for EVERYTHING.
But regardless, we're gonna have to give it a few years to get a Swift ecosystem even trying to get on the mic in the same venues as Java/JDK.