Hi Raj,
I think your interpretation is technically sound, that is, that Data merely has to implement DBAccess (but does not necessarily have to be declared with an explicit "implements DBAccess" clause). So if can do the following with your code without a compilation error
you should be OK:
However, put yourself in the position of the Sun grader. One of the requirements he has to check is that your Data class implements the DBAccess interface. The following sure makes his job easier:
So, if it's possible for you to be explicit I think it's to your advantage. It's a pretty good idea, in my opinion, to give the grader as much assistance as he needs to give you the full 400 points on the exam.
Hope this helps,
George
Regards, George
SCJP, SCJD, SCWCD, SCBCD