Excel isn't a database. It's a spreadsheet. Accessing it as a database would only lead to trouble. Use the appropriate API to interact with Excel files. Commonly used one is Apache POI HSSF/XSSF.
Alternatively, if your sole purpose is to have an embedded database in your application, then look for JavaDB (included since JDK6), Derby (its predecesor) or Hypersonic. No, MSAccess is not a good alternative, no.
On the other hand, this is the very moment in your carreer where you can make the difference.
Suffer the pain to get it done, ignore the voice in the back of your head that is nagging you,
and deliver a smart and well designed interface.
Delivering it might create goodwill that allows you to get your way on other decisions.