Why don't you use XML data representation?
Using XML is not trying to use all *Hi-Tech* methodologies in you program, but trying to be flexible and manipulate the info in a efficient manner
When you parse the XML, you automatically get the DOM tree representation. From there on its very easy to do any kind of query/manipulation like variable Bonus, and other operation you might want to introduce later�
Any day, I would vouch for XML data representation rather than flat files using string delimiters. (Not because the data storage looks neat and orderly, but because the kind of operations I can do with XML data representation. Also Java+XML work really well together.!!)
-Srivats