JavaFX with Scne Builder - Bouncing Ball

Controller.java

package sample;

import javafx.animation.Animation;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.geometry.Bounds;
import javafx.scene.layout.AnchorPane;
import javafx.scene.shape.Circle;
import javafx.util.Duration;

import java.net.URL;
import java.util.ResourceBundle;

public class Controller implements Initializable {

    @FXML
    private AnchorPane scene;

    @FXML
    private Circle circle;

    //1 Frame evey 10 millis, which means 100 FPS
    Timeline timeline = new Timeline(new KeyFrame(Duration.millis(10), new EventHandler<ActionEvent>() {

        double deltaX = 2;
        double deltaY = 2;

        @Override
        public void handle(ActionEvent actionEvent) {
            circle.setLayoutX(circle.getLayoutX() + deltaX);
            circle.setLayoutY(circle.getLayoutY() + deltaY);

            Bounds bounds = scene.getBoundsInLocal();
            boolean rightBorder = circle.getLayoutX() >= (bounds.getMaxX() - circle.getRadius());
            boolean leftBorder = circle.getLayoutX() <= (bounds.getMinX() + circle.getRadius());
            boolean bottomBorder = circle.getLayoutY() >= (bounds.getMaxY() - circle.getRadius());
            boolean topBorder = circle.getLayoutY() <= (bounds.getMinY() + circle.getRadius());

            if (rightBorder || leftBorder) {
                deltaX *= -1;
            }
            if (bottomBorder || topBorder) {
                deltaY *= -1;
            }
        }
    }));


    @Override
    public void initialize(URL url, ResourceBundle resourceBundle) {
        timeline.setCycleCount(Animation.INDEFINITE);
        timeline.play();
    }
}

Main.java

package sample;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
        primaryStage.setTitle("Hello World");
        primaryStage.setScene(new Scene(root));
        primaryStage.show();
    }


    public static void main(String[] args) {
        launch(args);
    }
}

sample.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.shape.Circle?>


<AnchorPane fx:id="scene" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/15.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
   <children>
      <Circle fx:id="circle" fill="DODGERBLUE" layoutX="100.0" layoutY="200.0" radius="25.0" stroke="BLACK" strokeType="INSIDE" />
   </children>
</AnchorPane>