It depends what you want to do.
Web development: PHP, Python, or Perl
Stand alone system application:
On Windows: C# or possibly Visual Basic
On Linux: C, C++ with the QT libraries
which language you choose greatly depends on what you want to do, specifically.
C is a very low level language. Its fairly basic, but you have to write a LOT of code to do anything useful. C++ is slightly higher level (only marginally though), and has objects. Java is a full fledged language (like C++ or C), but has lots of built in libraries for doing useful things like network communication, handling non-ASCII strings, creating graphical interfaces, etc.
C++ alongside QT isn't too bad, because QT adds lots of libraries too C++ making it very similar too Java. C++ will teach you the differences between pointers, references, and "primitives" (I know, I know, its a Java term).
Depends what you want to do :)