JavaFX mon objet Rectangle ne s'affiche pas

package application;
	
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.scene.shape.Shape;


public class Main extends Application {
	@Override
	public void start(Stage primaryStage) {
		try {
			Group root = new Group();
			Scene scene = new Scene(root,400,400);
			
			Rectangle r = new Rectangle();
			r.setX(750);
			r.setY(100);
			r.setWidth(200);
			r.setHeight(100);
			r.setArcWidth(30);
			r.setArcHeight(20);
			
			root.getChildren().addAll(r);
			
			primaryStage.setScene(scene);
			primaryStage.setTitle("Hello World");
			primaryStage.show();
		} catch(Exception e) {
			e.printStackTrace();
		}
	}
	
	public static void main(String[] args) {
		launch(args);
	}
}