in my opinion, the answers to your two questions are both yes. You have to comply with the assignment instructions, and regarding the DB interface and the Data class, it states that : "Data.java must implement the DB interface".
There is no restriction on other interfaces that Data must or must not implement. And stritcly speaking, implementing a subclass of DB means implementing DB.
SCJP 1.5<br />SCJD 1.6<br />SCBCD in progress...
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com