Check out this link which I feel would perfectly address your question. In my experience in the information field, I can say that Java will probably be around for a while, after all its been here since the mid 90's, and that must mean something.
Java is a full-scale programming language with a vast API library of thousands of functions that you can use for a huge range of systems. It's very widely used to program complex commercial application and servers. It's a serious investment of time and effort to learn to use it well.