I am currently working with Jörg on the betsy tool which compares the WS-BPEL 2.0 conformance of open source WS-BPEL 2.0 engines. At the end of a successful comparison run, html reports are generated and can be opened by the user via the browser. I often had to execute such a betsy run in different configurations and wanted to look at the results only. The problem is that you have to wait until the run is completed (no notifications available), open the windows explorer, navigate to the correct folder and open the html file. This process can be shortened by using bookmarks in the browser for the results. However, this does not solve the problem on being notified after the run is completed. Regardless, I have found a very simple solution: the java.util.Desktop class.
This class is shipped with the Java SE edition since Version 6 and can be used to open the default browser at a specific URI, open the default mail application (even open the compose mail window) or open/print a specific file using the registered application for this file type. I created a few examples in groovy code to show you how simple this functionality can be used as mostly only one import statement and one code statement is required. The code is written in groovy, however, it is also compatible with Java code. Just copy the import statement to the top of the Java class and past the other code line where you want to execute it.
Moreover, you can open a file using the default editor, too. As some operation systems may not support this class, you can check with the static method Desktop.isDesktopSupported() whether it is possible to use this functionality in general. For more information using this class, please refer to the Javadoc documentation.