JavaFX 2.0: set width and height of Layout Pane - setPrefSize()

package javafx_layoutpanes;

import javafx.application.Application;
import javafx.geometry.Rectangle2D;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.paint.Color;
import javafx.scene.text.Text;
import javafx.stage.Screen;
import javafx.stage.Stage;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class JavaFX_LayoutPanes extends Application {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }
    
    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("java-buddy.blogspot.com:");
        Group root = new Group();
        Scene scene = new Scene(root, 400, 300);
        
        BorderPane borderPane = new BorderPane();
        borderPane.setPrefSize(scene.getWidth(), scene.getHeight());
        
        borderPane.setTop(new Button("Top"));
        borderPane.setBottom(new Button("Bottom"));
        borderPane.setCenter(new Button("Center"));
        borderPane.setLeft(new Button("Left"));
        borderPane.setRight(new Button("Right"));
        
        root.getChildren().add(borderPane);
        primaryStage.setScene(scene);
        primaryStage.show();
    }
}