The answer "yes" is the correct one, but you probably want a little more detail.
In my opinion (and it is just an opinion), you should learn as many programming languages as you have time for. However, you need to first get a handle on some of the basic concepts.
You've already started with Java, which would not have been my first choice but you are where you are, not where I'd like you to be. So get comfortable with Java andthen move on to C - not C++ or Objective-C, just plain C. The reason for this is that both C++ and Objective-C are based on C, so learning C will give you a start in both of those languages. In particular, you need to understand what a pointer is and how it works in C.
Then you can learn Objective-C and/or C++. Objective-C is much easier (and, in my opinion, better) than C++, so I'd start with it, except for the fact that you will want to be writing real useful programs with them. Unless you are programming for OS X or iOS, C++ will be more useful in the long term.
You also should learn some other languages like Ruby or Python also some version of Lisp or perhaps Haskell.