Computer Science 252
Problem Solving with Java

Spring 2014, The College of Saint Rose

FallingBallButtonsPanel Demo

A working demo of FallingBallButtonsPanel will appear below. Click inside the applet to interact with it.

FallingBallButtonsPanel BlueJ Project

Click here to download a BlueJ project for FallingBallButtonsPanel.

FallingBallButtonsPanel Source Code

The Java source code for FallingBallButtonsPanel is below. Click on a file name to download it.

import objectdraw.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JPanel;

 * Example FallingBallButtons: adding Swing JButtons to the
 * falling ball, but in a JPanel all at the bottom of the window
 * Jim Teresco, The College of Saint Rose, Fall 2013
 * Based on example from Williams College CS 134.
 * $Id: 2221 2013-10-22 02:48:35Z terescoj $

// First, note above the extra import statements for additional Java API
// classes and interfaces we are using here.

// Now, notice that we have "implements ActionListener" specified on our
// WindowController class.  More on that below.
public class FallingBallButtonsPanel extends WindowController implements ActionListener {
    private static final int SLOW_SPEED = 2;
    private static final int MEDIUM_SPEED = 5;
    private static final int FAST_SPEED = 10;

    // JButtons to create falling balls of different speeds
    private JButton slowButton, mediumButton, fastButton;

    public void begin() {
        // the canvas doesn't have to be quite as big here.
        setSize(500, 500);
        // We still need our content pane
        Container contentPane = getContentPane();
        // But now we'll create a JPanel, which we will then use
        // to group together our JButtons.
        JPanel southPanel = new JPanel();

        // next, we'll create some buttons and add them to our
        // JPanel instead of to the content pane.  Note that
        // we do not tell them to go into a particular place 
        // in the JPanel, just add them and let the JPanel
        // choose a layout in this case.
        slowButton = new JButton("Drop Slow Ball");

        mediumButton = new JButton("Drop Medium Ball");

        // fast button in the east (right)
        fastButton = new JButton("Drop Fast Ball");
        // now, we add the JPanel (which contains our JButtons)
        // to the content pane, in the south
        contentPane.add(southPanel, BorderLayout.SOUTH);

        // add our action listeners as before

        // put at end of all methods that change the layout

    // Same actionPerformed method as before.
    public void actionPerformed(ActionEvent e) {
        double speed;

        if (e.getSource() == slowButton) {
            speed = SLOW_SPEED;
        else if (e.getSource() == mediumButton) {
            speed = MEDIUM_SPEED;
        else {
            speed = FAST_SPEED;
        new Ball(new Location(200, 0), speed, canvas);

import objectdraw.*;
import java.awt.*;

 * Example FallingBallUglyButtons: 
 * A Ball that will drop to the bottom of the canvas.
 * Jim Teresco, The College of Saint Rose, Fall 2013
 * $Id: 2221 2013-10-22 02:48:35Z terescoj $

public class Ball extends ActiveObject {
    private static final int BALL_SIZE = 30;
    private static final int PAUSE_TIME = 30;

    // The representation of the ball on the screen
    private FilledOval ball;

    // The bottom of the playing area
    private int bottomHeight;

    private double ySpeed;

    // Construct a new Ball with the given starting location and y velocity.
    public Ball(Location point, double speed, DrawingCanvas aCanvas) {
        ball = new FilledOval(point, BALL_SIZE, BALL_SIZE, aCanvas);
        ySpeed = speed;
        bottomHeight = aCanvas.getHeight();

    public void run() {
        while (ball.getY() < bottomHeight) {
            ball.move(0, ySpeed);