if you want to learn online, w3schools is great.
Java for web or also known as the J2ee platform, is composed of packages and libraries for creating a web application (that is dynamic web page applications ).
In my opinion Java is neede anywhere you have to deal with animation, it goes on the same track as flash does, they're fullfilling each other. However it is hard to learn it by yourself, but it is not imposible . web schools are great but if you can find a guy that could show you a thing or two, would be much better. In such cases you'll have the answers right next to you instead of searching on net for the solutions for your particular problem.
i use it a lot