Как изменить панель в зависимости от выбора?

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.FlowPane;
import javafx.scene.layout.Pane;
import javafx.stage.Stage;
import java.util.function.Supplier;
public class Main extends Application {
    public void start(Stage primaryStage) throws Exception {
        final BorderPane rootScene = new BorderPane();
        TreeItem<NamePaneFactory> root = new TreeItem<>(new NamePaneFactory("Root", () -> null));
        root.getChildren().addAll(
                new TreeItem<>(new NamePaneFactory("Pane1", Pane1::new)),
                new TreeItem<>(new NamePaneFactory("Pane2", Pane2::new))
        );
        TreeView<NamePaneFactory> treeView = new TreeView<>(root);
        treeView.getSelectionModel().selectedItemProperty().addListener((observable, oldValue, newValue) -> {
            rootScene.setCenter(newValue == null ? null : newValue.getValue().factory.get());
        });
        rootScene.setLeft(treeView);
        primaryStage.setScene(new Scene(rootScene));
        primaryStage.show();
    }
    static class NamePaneFactory {
        final String name;
        final Supplier<? extends Pane> factory;
        public NamePaneFactory(String name, Supplier<? extends Pane> factory) {
            this.name = name;
            this.factory = factory;
        }
        @Override
        public String toString() {
            return name;
        }
    }
    static class Pane1 extends BorderPane {
        public Pane1() {
            super(new Label("Pane1"));
        }
    }
    static class Pane2 extends FlowPane {
        public Pane2() {
            super(new Label("Pane2"));
        }
    }
}