reset my application by pressing a new game button. javafx
<p>We are making checkers and im trying to get the new game button to restart the application but all it does now is shutting it down. we have tried some things but not gotten far,</p>

<pre><code>@Override
    public void start(Stage primaryStage) throws Exception {
        Button btnNewGame = new Button("New Game");
        Button btnTutorial = new Button("Tutorial");

        btnTutorial.setText("Tutorial");
        btnTutorial.setOnAction (new EventHandler&lt;ActionEvent&gt;() {


            public void handle (ActionEvent event) {

                if (Desktop.isDesktopSupported()) {
                    try {
                        File brukermanual = new File("Brukermanual.pdf");
                        Desktop.getDesktop().open(brukermanual);
                    } catch (IOException exception) {

                    }
                }
            }
        });

         btnNewGame.setOnAction( __ -&gt;
            {
              System.out.println( "Restarting app!" );
              primaryStage.close();
            } );
            primaryStage.setScene( new Scene( new BorderPane( btnNewGame ) ) );
            primaryStage.show();

        ToolBar toolBar = new ToolBar();
        toolBar.getItems().addAll( new Separator(), btnNewGame, btnTutorial);

        BorderPane pane = new BorderPane();

        pane.setTop(toolBar);
        pane.setCenter(createContent());

        Scene scene = new Scene(pane, 640, 675);

        primaryStage.setTitle("Dam spill - OBJ2000 Eksamen 2016");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
</code></pre>