Apache POI-HSSF and POI-XSSF
- every elaborate API
- works with xlsx files
JExcelAPI
- lightweight API, easier to learn
- MUCH faster on big spreadsheets (10000's of lines)
- no support (yet?) for Excel 2007+ xlsx files
Have a look at jXLS as well, it's a library on top of POI that allows you to use Excel files as templates.
