This week's book giveaway is in the General Computing forum. We're giving away four copies of Arduino in Action and have Martin Evans, Joshua Noble, and Jordan Hochenbaum on-line! See this thread for details.
For more information on using any of the J2SE classes, The API Specification is a good place to begin to understand what a class or instances of a class do and how to use them. Of course, asking questions and searching past conversations at JavaRanch ain't bad either.