As you are doing C/C++, you should go for C# because your basics will be revised while learning. Moreover C# is faster to develop in (especially GUI design), has a better IDE then any of the various Java IDEs out there, can perform lower level operations (fixed statements and unsafe code). For online tutorials you can try these sites http://edufire.com http://www.programmingtutorials.com/
I think you can do much more with Java, the tutorials recommended above are perfect to start of with Java, thats where I started myself
________ affair Cam