For example, one application that I'm working on stores PDF files into a database, then can pull them back out for display. I've got a call in there using Runtime.exec to do a "cmd /c start " plus the PDF filename. Works great for Windows. Would prefer to find a platform independent way (trying to avoid OS detection with alternate methods for various OS) to do this though as we also run the software on Solaris and Mac.
Look at Desktop which has a open method and that would be platform independent.
Launches the associated application to open the file.