The POI project contains several components for dealing with popular OLE 2 formats in Java. POIFS is a pure Java implementation of the OLE 2 Compound document format. HSSF is a pure Java implementation of Excel 97-2003 XLS file format based on POIFS. HSSF Serializer is a pure Java serializer for Cocoon 2 that uses the Gnumeric XML format to output XLS. Full documentation of the POIFS file format is included. It is useful if you wish to output reports in the Excel file format, or if you have existing XML documents that you need to get into Excel. HSLF provides initial support for PowerPoint 97-2003 and HWPF provides limited support for Word 97-2003. POIFS can be used to read any OLE2 stream.
Support for evaluating formulas in HSSF, initial support for HSLF (PowerPoint), and support for editing document properties (HPSF).
URL: Jakarta POI - Java API To Access Microsoft Format Files