I think you should learn several languages (web, mobile and desktop) to determine your future career. You'll never know which one you like if you don't try.
Web: Stick to the usual PHP + JS (and their usual cohort of HTML + CSS + MySQL). Maybe for a year. Then feel free to expand your horizon to their competitors such as Ruby or NodeJs like already said.
Desktop: Since you're already in Java, I recommend C# and its usual companion MSSQL.
Mobile: maybe Swift (ios only), PhoneGap (HTML/CSS/JS) or Xamarin (C#).
No need to mastering that all, just have a good grasp of them. In two years (I believe it's the age where you'll enter university or college?) you'll know what you need to learn and what education to take.
I believe desktop is still where the most money is (for office career and B2B project), but web is rising and you could easier selling small things (small library, templates), big things (subscription based maybe) or selling programming service across the world, and with mobile you obviously even easier to sell things in form of app in their respective marketplace.