JWorkbook is a free library for Java that can generate spreadsheet files in Gnumeric and Excel format.

See:
Description

Packages

org.jfree.workbook	The root package for the JWorkbook class library.
org.jfree.workbook.date	Date classes copied from the JCommon class library.
org.jfree.workbook.io	Input/output classes.

JWorkbook is a free library for Java that can generate spreadsheet files in Gnumeric and Excel format.

Please visit http://www.jfree.org/jworkbook/index.html for the latest information about JWorkbook.