Every programming language is worth learning. Each one has it's strengths and weaknesses, so it doesn't matter too much which one you choose. It is possible to write hacks in Java, though you need to know the language inside-out, and it's much more complicated and slow than it would be in c++ or c#. If you want your code to be easily ported to almost every platform that exists today, go with Java. C# isn't very portable, but thankfully most people use windows. C++ isn't hard to port either, all that changes are the libraries that are available. So, basically, yes: Java is definitely worth learning. It's a great language and it's great for networking and security. I'm fairly sure the standard libraries for Java have networking and security and all that hoo-blah. My advice is learn c++ and perhaps a little assembly if you really want to. Use c++ to do your low-level programming and link your modules to other languages like C# and Java, or even scripting languages like Python, Lua, or Ruby. Blah, I'm a noob, don't listen to me. I'm tired and drunk.
