[nus-cs2103-AY1718S1#39] executable jar file doesn't run (nus-cs2103-…

…AY1718S1#62)

When running it in .jar, Java does not allow the use of '\' (Windows
file separator), only allows '/' (Unix file separator), in resource
filepaths.

To ensure that future developers understand the issue, a link to the
documentation is provided.

src/seedu/addressbook/ui/Gui.java

@@ -36,7 +36,12 @@ public void start(Stage stage, Stoppable mainApp) throws IOException {
 
     private MainWindow createMainWindow(Stage stage, Stoppable mainApp) throws IOException{
         FXMLLoader loader = new FXMLLoader();
-        loader.setLocation(Main.class.getResource("ui" + File.separator + "mainwindow.fxml"));
+
+        /* Note: When calling getResource(), use '/', instead of File.separator or '\\'
+         * More info: http://docs.oracle.com/javase/8/docs/technotes/guides/lang/resources.html#res_name_context
+         */
+        loader.setLocation(Main.class.getResource("ui/mainwindow.fxml"));
+
         stage.setTitle(version);
         stage.setScene(new Scene(loader.load(), INITIAL_WINDOW_WIDTH, INITIAL_WINDOW_HEIGHT));
         stage.show();