Launching an Mac application from Java on OS X is just a matter of invoking the built-in open
command with the Application as a parameter. The open command line tool in OS X knows how to correctly open many different file types, including application bundles. If you were trying to launch the TextEdit.app application, you would invoke:
open /Applications/TextEdit.app
In Java, you would use:
String cmd = "open /Application/TextEdit.app";
Process p = Runtime.getRuntime().exec(cmd);