Hi Abiodun,
You might be interested in looking at
this post where you can find the TOC for my book.
We have addressed both accessing data from file and record locking differently in the new book compared to how it was in the first edition. These are now closer to the problems you will encounter in the real assignment. However as with the first edition, we cannot just give the solutions away (and we believe you would not want us to), so there are differences between our sample project (and it's associated record locking) and your real assignment.
In chapter 5 we briefly discuss using the singleton pattern with the Data class, and why we decided against it. We also consider it with some other classes in that same chapter, giving reasons for and against using the singleton pattern.
Regards, Andrew