OK, I want to start a new course in the new year, but I'm stuck as to which. I want to move into app development but haven't even decided on ios or android!

My doubts:

Java - the big daddy obviously, but will it always remain so? Any chance of Android dumping it and doing something proprietary in the next few years? As a core object oriented language, I've always thought Java would be very useful to know. I dabbled in it at start of year so know the basics already. Would learning Java give me a good grounding in everything else related to this field?

Objective-C/Swift - the iOS field confuses me a little. Ob-C seems to have been dumped in favour of Swift. I already know that Apple can be temperamental because I have some apps out there, so already see things from the dev side of the curtain. How similar are these languages to Java? Would learning Java then help me to learn Swift quickly?

I'm leaning towards Java, I have to say. I have my apps in iOS and learning Swift would open the possibility of taking over the dev side of things BUT learning Java could enable me to put the app onto Android which would be great.

Any advice or tips greatly appreciated.