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.
If you are doing linux java development GET THIS
If you're on linux and doing java development get this tool. It was easy to install, its VERY useful.
My only issues is I wish the GUI were in a different thread then the JVM and I could use it in the debugger. (That would be completely awesome). At the very least a text dumping version with the gui turned off using a configurable rate would be cool too. It wouldn't hurt if it were a bit faster. All in all this project rocks. I use it on POI all the time. Its helped me optimize soo much. THANK YOU, THANK YOU!