Steve Metsker's and my recent book, Design Patterns in Java, has had a sample chapter posted at InformIT: Adapter.
If you're not familiar with Adapters, or need to brush up on them, you might find this chapter helpful. (The extract didn't include our solutions; let me know if you need help.)
Steve Metsker and I have co-written Design Patterns in Java, available from Addison-Wesley. This is a workbook-style book, updating Steve's earlier Design Patterns Java Workbook and Design Patterns in C#. It covers the same 23 patterns as Design Patterns, but adds some different perspective and a number of challenges to help you make sure you understand the patterns.
It's targeted to...