Been friends with Java for years, recently trying out Objective-C and QTP. Here are some of the answers I really had fun writing:

Web Services

1. SOAP, REST and the Horse named HTTP

2. Multi-Port Services and Shipping Docks

3. How MTOM Works: Going Bananas

4. The Value of WS-Addressing

Core Java

1. Interface: Implement Me or Else

2. Generic who?

3. Get Me, Set Me

4. Hey! You're sharing my object!

5. Encapsulation and Security