Reading an OpenOffice file is not as simple as reading a plain text file, simply because OpenOffice contains a lot more features than a plain text editor.
The OpenOffice Java API
OpenOffice can read a number of file formats, and makes them accessible through its API. A starting point might be this article and of course the OO developer site Some introductory information about the OO file format can be found here and here - basic Java code for reading OO files is here
After doing that it renders the files as folders/directories instead of just files.