How to replace a scene component with a button click inJavaFX - javafx-8

Question

Am new to JavaFX and changing only a component of a scene on button click while other components of the scene remain unchanged is giving me hard times.
I have a splitpane with 2 divisions. One part containing a HBox with buttons and a VBox on the other. How can I replace the VBox depending on button clicked ? thanks in advance, Below is my sample code:
public class ShoolLibrary extends Application {
BorderPane b_pane;
SplitPane common;
Scene scene;
#Override
public void start(Stage primaryStage) {
primaryStage.setTitle("The Library");
b_pane = new BorderPane();
common = commonGround();
b_pane.setCenter(common);
scene = new Scene(b_pane, 700, 480);
primaryStage.setScene(scene);
primaryStage.show();
}
//Main Content
private SplitPane commonGround(){
HBox hb = new HBox(); //Holds Buttons for Action
VBox vb = new VBox(); //This should change depending on button click
Button btn1 = new Button("library profile");
Button btn2 = new Button("Books");
Button btn3 = new Button("Members");
//Button Action
btn1.setOnAction(actionEvent -> /*Replace vb with profile()*/);
btn2.setOnAction(actionEvent -> /*Replace vb with books()*/);
btn2.setOnAction(actionEvent -> /*Replace vb with members()*/));
hb.getChildren().addAll(btn1,btn2,btn3);
SplitPane sp = new SplitPane();
sp.setOrientation(Orientation.HORIZONTAL);
sp.getItems().addAll(hb,vb);
return sp;
}
private VBox profile(){
txt = new Text("Inside library profile");
VBox vbx1 = new VBox();
vbx1.getChildren().add(txt);
return vbx1;
}
private VBox books(){
txt = new Text("Inside books");
VBox vbx1 = new VBox();
vbx1.getChildren().add(txt);
return vbx1;
}
private VBox members(){
txt = new Text("Inside Members");
VBox vbx1 = new VBox();
vbx1.getChildren().add(txt);
return vbx1;
}
public static void main(String[] args) {
launch(args);
}
}

Answer 1

How about using a wrapper pane in which you place your vBoxes?
Pane wrapperPane = new Pane();
sp.getItems().addAll(hb, wrapperPane);
then:
VBox library = profile()
btn1.setOnAction(actionEvent ->
wrapperPane.getChildren().clear();
wrapperPane.getChildren().add( library );
);
VBox books = books()
btn2.setOnAction(actionEvent ->
wrapperPane.getChildren().clear();
wrapperPane.getChildren().add( books );
);
and so on...