Questions like these can only be answered with "what do you want to do?"
If you want to design computer applications, continuing Java or learning C++ is a good start. If you want to do modeling, there's languages for that, too (I don't know any off my head but I think Python is one).
My only suggestion is to pick a language that will allow you to do most everything you want and hammer away at it. Do a project each week, or try to figure out someone's code. Dive right in. I found that really knowing one language was enough and made learning other languages very easy. Ifs, and whiles, and for loops all pretty much do the same thing in every language. Just the syntax might be different.
If you learn the meat-and-potatoes of programming -- the stuff that is in mostly every language -- then all that's left to learn in regard to other languages is language-specific stuff. For example, say you're a master of C++ but for a class or work you need to switch to Java. You know Object Oriented programming, so all you'll need to learn is the Java-specific classes, methods, and stuff like that.
Good luck!