Check out POI and jExcelAPI; those are the only notable free Java libraries that can work with Excel files. They're linked on the http://faq.javaranch.com/java/AccessingFileFormats page. I'm not sure what either can do with Pivot tables, specifically, though.
Yes, POI is a great project that implement the excel operation with Java. However, there was still a weak point for POI. POI can 'operate' the 'existing' Pivot table, but not 'create' a new pivot table in the excel file.
It is the reason why I hope to find a new free lib.
Thank you anyway.
I am looking forwards more answers for my question... [ October 15, 2008: Message edited by: Wei GENG ]