This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
As far as I know, this information is not available through the standard API. If you know the physical location to the folder or JAR file (which you might be able to extract from System.getProperty("java.class.path") you could try to look there for the .class files, but that's about as far as you'll get.