Assuming one wishes to maintain the integrity of the MVC design pattern, it would be unfeasible for FXML files and controller files to have to be located in the same package directory in order for the FXML file to register the controller file's intent to associate itself as the FXML file's controller.

please see: http://code.makery.ch/java/javafx-8-tutorial-part2/

particularly: the comment section at the bottom of the tutorial, the brief exchange between myself and the blog's author, Mr. Marco Jakob