I am taking a programming class next school year (high school), and I would like to know whether C++ or Java is more conducive to hacking in general. Perhaps I will use Linux. This is important to me, because it is the beginning of my career.

C++

C++ is still very much the industry standard for much programming. Learn it and you will have an inside track on most programs. Java I can not see helping much in the way of hacking. Sun took many precautions for security while developing it.

Java sucks, go C++

Java rocks. But for what he wants, C++ is the far better choice

Java is a very powerful language, i'd be impressed by anyone who takes the time to learn it; but in this case the guy wants to make programs which as Pergesu pointed out c++ would be a good choice.