This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
I would concentrate on the File class first. then study all the streams classes: FileInputStream, ObjectInputStreamDataInputStreamBufferedInputStream (ocourse noth the output too). then learn the Reader/writer ones: FileReader, BufferedReader etc... learn the difference between the reader/writer to input/output (the first deal with char and the second with bytes). undersatnd the interface Serializable and what it is used for. thats about it i think