Be sure that any Java reference book you choose includes Java 5 (aka Java 1.5) and / or Java 6 (aka Java 1.6).

Please feel free to recommend your favorite book for inclusion in this list.

1. Java Software Solutions, 5th Edition, Lewis & Loftus
   Addison-Wesley Publishing, ISBN: 0-321-40949-3
2. Java Concepts, 5th Edition, Cay Horstmann
   Wiley Publishing, ISBN: 978-0-470-10555-9
3. Ivor Horton's Beginning Java 2, JDK 5 Edition, Ivor Horton,
   Wrox Publishing, ISBN: 0-7645-6874-4