(Remove the largest ball first) Modify Listing 20.6, MultipleBallApp.java to assign a random radius between 2 and 20 when a ball is created. When the - button is clicked, one of largest balls is removed

/*********************************************************************************
* (Remove the largest ball first) Modify Listing 20.6, MultipleBallApp.java to   *
* assign a random radius between 2 and 20 when a ball is created. When the -     *
* button is clicked, one of largest balls is removed.                            *
*********************************************************************************/
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.beans.property.DoubleProperty;
import javafx.geometry.Pos;
import javafx.scene.Node;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollBar;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.util.Duration;
import java.util.*;

public class Exercise_20_09 extends Application {
	@Override // Override the start method in the Application class
	public void start(Stage primaryStage) {
		MultipleBallPane ballPane = new MultipleBallPane();
		ballPane.setStyle("-fx-border-color: yellow");

		Button btAdd = new Button("+");
		Button btSubtract = new Button("-");
		HBox hBox = new HBox(10);
		hBox.getChildren().addAll(btAdd, btSubtract);
		hBox.setAlignment(Pos.CENTER);

		// Add or remove a ball
		btAdd.setOnAction(e -> ballPane.add());
		btSubtract.setOnAction(e -> ballPane.subtract());

		// Pause and resume animation
		ballPane.setOnMousePressed(e -> ballPane.pause());
		ballPane.setOnMouseReleased(e -> ballPane.play());

		// Use a scroll bar to control animation speed
		ScrollBar sbSpeed = new ScrollBar();
		sbSpeed.setMax(20);
		sbSpeed.setValue(10);
		ballPane.rateProperty().bind(sbSpeed.valueProperty());

		BorderPane pane = new BorderPane();
		pane.setCenter(ballPane);
		pane.setTop(sbSpeed);
		pane.setBottom(hBox);

		// Create a scene and place the in the stage
		Scene scene = new Scene(pane, 250, 150);
		primaryStage.setTitle("Exercise_20_09"); // Set the stage title
		primaryStage.setScene(scene); // Place the scene in the stage
		primaryStage.show(); // Display the stage
	}

	private class MultipleBallPane extends Pane {
		private Timeline animation;

		public MultipleBallPane() {
			// Create an animation for moving the ball
			animation = new Timeline(
				new KeyFrame(Duration.millis(50), e -> moveBall()));
			animation.setCycleCount(Timeline.INDEFINITE);
			animation.play(); // Start animation
		}

		public void add() {
			Color color = new Color(Math.random(),
				Math.random(), Math.random(), 0.5);

			// Assign a random radius between 2 and 20
			double radius = 2 + Math.random() * 19;
			getChildren().add(new Ball(30, 30, radius, color));
		}

		/** Remove one of the largest balls */
		public void subtract() {
			if (getChildren().size() > 0) {
				ArrayList<Node> nodes = new ArrayList(getChildren());
				ArrayList<Ball> balls = new ArrayList(nodes);
				getChildren().remove(Collections.max(balls));
			}
		}

		public void play() {
			animation.play();
		}

		public void pause() {
			animation.pause();
		}

		public void increaseSpeed() {
			animation.setRate(animation.getRate() + 0.1);
		}

		public void decreaseSpeed() {
			animation.setRate(
				animation.getRate() > 0 ? animation.getRate() - 0.1 : 0);
		}

		public DoubleProperty rateProperty() {
			return animation.rateProperty();
		}

		protected void moveBall() {
			for (Node node: this.getChildren()) {
				Ball ball = (Ball)node;
				// Check boundaries
				if (ball.getCenterX() < ball.getRadius() ||
					 ball.getCenterX() > getWidth() - ball.getRadius()) {
					ball.dx *= -1; // Change ball move direction
				}
				if (ball.getCenterY() < ball.getRadius() ||
					 ball.getCenterY() > getHeight() - ball.getRadius()) {
					ball.dy *= -1; // Change ball move direction
				}

				// Adjust ball position
				ball.setCenterX(ball.dx + ball.getCenterX());
				ball.setCenterY(ball.dy + ball.getCenterY());
			}
		}
	}

	class Ball extends Circle implements Comparable<Ball> {
		private double dx = 1, dy = 1;

		Ball(double x, double y, double radius, Color color) {
			super(x, y, radius);
			setFill(color); // Set ball color
		}

		@Override // Implement the compareTo method defined in Comparable
		public int compareTo(Ball ball) {
			if (getRadius() > ball.getRadius())
				return 1;
			else if (getRadius() < ball.getRadius())
				return -1;
			else
				return 0;
		}
	}
}