HSLF is the POI Project's pure Java implementation of the Powerpoint '97(-2007) file format. It does not support the new PowerPoint 2007 .pptx file format, which is not OLE2 based.
HSLF provides a way to read, create or modify PowerPoint presentations. In particular, it provides:
The quick guide documentation provides information on using this API. Comments and fixes gratefully accepted on the POI dev mailing lists.