Excel Files

I am interested in trying to create my own Excel reader/writer Library. I know Excel Files are essentially xmls, but I wanted to know if I had to do something special to read in Excel Files or how it works.

If anyone can give me any information on how Excel Files work, it would be appreciated.

Why recreate the wheel?

There are already several Java libraries out that handle Excel read/write functions, one of which is developed by Apache.

Look into Apache's POI, or JExcelApi.