It is pretty easy to start a WWW browser from a Java application. The Desktop class in the java.awt package has a static method named getDesktop() that returns a Desktop object that can be used for this purpose. You just needs to construct a URI object (from the java.net package) and pass it to the Desktop object's browse() method. For example:

Desktop desktop = Desktop.getDesktop();
URI     uri     = new URI("http://www.jmu.edu/");

desktop.browse(uri);

To read from the local file system you can use the file protocol rather than the http protocol.

URI objects and URL objects are closely related (and the distinction exists mostly for historical reasons). The URI class has a toURL() method that constructs a URL from a URI. Similarly, the URL class has a toURI() method that constructs a URI from a URL.