====== Bounce Example ======

Press the Button at the top to start and stop a ball that bounces and different angles

{{::screenshot_2023-05-15_at_6.13.35_am.png?400|}}

<code java Wall.java>
import java.awt.Color;
import java.awt.Graphics;
import java.awt.geom.Rectangle2D;
public class Wall {
    private Rectangle2D.Double rect;
    private Color color;
    private int x,y,width,height;
    public Wall(int x, int y, int width, int height){
        rect=new Rectangle2D.Double(x, y, width, height);
        this.x=x;
        this.y=y;
        this.width=width;
        this.height=height;
        setColor(Color.BLACK);
    }
    public boolean touches(Ball ball){
        return rect.intersects(ball.area());
    }
    public void draw(Graphics g){
        Color c=g.getColor();
        g.setColor(color);
        g.fillRect(x, y, width, height);
        g.setColor(c);
    }
    public void setColor(Color color) {
        this.color = color;
    }
    public Color getColor() {
        return color;
    }
}
</code>

<code java Ball.java>
import java.awt.Color;
import java.awt.Graphics;
import java.awt.geom.Rectangle2D;
public class Ball {
    private int x;
    private int y;
    private int radius;
    private int rise;
    private int run;
    private boolean visable; 
    public Ball(int radius){
        x=randInt(350,450);
        y=randInt(250,350);
        this.radius=radius;
        rise=randInt(1,8);
        run=randInt(-8,8);
        setVisable(false);
    }
    public int randInt(int min, int max){
        return min+(int)((max-min)*Math.random());
    }
    public void move(){
        x+=run;
        y+=rise;
    }
    public void bounceVertical(){
        rise*=-1;
    }
    public void bounceHorizontal(){
        run*=-1;
    }
    public void draw(Graphics g){
        if (visable){
            Color c=g.getColor();
            g.setColor(Color.BLUE);
            g.fillOval(x-radius, y-radius, 2*radius, 2*radius);
            g.setColor(c);
        }        
    }
    public void setVisable(boolean visable) {
        this.visable = visable;
    }
    public boolean isVisable() {
        return visable;
    }
    public Rectangle2D area(){
        return new Rectangle2D.Double(x-radius, y-radius, 2*radius, 2*radius);
    }
    public void setRise(int rise){ this.rise=rise;}
    public void setRun(int run){ this.run=run;}
    public int getRise(){return rise;}
    public int getRun(){return run;}
}
</code>

<code java Bounce.java>
/**
 * A Sample Animation with a Restart button
 * 
 * @author Fr Chris Thiel, OFMCap
 *  Applet version 12 May 2011
 *  Application Version May 12, 2023
 */

import java.awt.event.*; 
import java.applet.Applet;
import java.awt.*;
import java.io.IOException;

import javax.swing.*;

public class Bounce extends JPanel implements  ActionListener
{
    //EasySound boing;
    public static int WIDTH=800;
    public static int HEIGHT=650;
    private Timer timer;
    //Image virtualMem;
    //Graphics gBuffer;
    private Ball ball;
    private Wall top,bottom,left,right;
    private int appletWidth;        
    private int appletHeight; 
    private int frame;
    private int lastFrame;
    private Button myButton;
    private int count;
    private EasySound boing;
    
    public Bounce()
    {
        boing = new EasySound("boing.wav");
        boing.play();
       
        ball = new Ball(10);
        top = new Wall(0,0,800,10);
        bottom = new Wall(0,590,800,10);
        left = new Wall(0,10,10,590);
        right = new Wall(790,10,10,590);
        appletWidth = getWidth();
        appletHeight = getHeight(); 
        frame=0;
        timer=new Timer(1, this);
        lastFrame=appletWidth;
        count=0;

        myButton= new Button("Do It Again");
        //the class is its own button listener
        myButton.addActionListener (this);
        add(myButton);      
    }
    public static void main(String[] args) {
        Bounce app= new Bounce();
        JFrame window = new JFrame("Bounce Example");
        window.setSize(WIDTH, HEIGHT);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.getContentPane().add(app);
        //window.addKeyListener(app);
        //window.pack();
        window.setVisible(true);

    }
     public void paintComponent(Graphics g)
    {
        //We draw using the object methods of
        // the graphics buffer, not what is
        // currently on the screen
         super.paintComponent(g);
        g.setColor(Color.white);
        g.fillRect(0,0,appletWidth,appletHeight);
        g.setColor(Color.black);

        g.setColor(Color.black);
        g.drawString("Frame "+frame, 20,20);
        g.drawString(count+" bounces", 20, 35);
        ball.draw(g); 
        top.draw(g);
        bottom.draw(g);
        left.draw(g);
        right.draw(g);

        //Now we send the result to the screen
        //g.drawImage(virtualMem,0,0,this);
    }
    public void update(Graphics g)
    {
        paint(g); //get rid of flicker with this method
    }
    /**
     * ActionListener is an interface and
     * requires the actionPerformed() method
     * to be defined..in this case we
     * look for a restart button being pressed
     */
    public void actionPerformed(ActionEvent e){
        Object source = e.getSource();
        if (source == timer) {
                frame++;
                frame%=100;
                ball.move();
                if (top.touches(ball) || bottom.touches(ball)){
                    ball.bounceVertical();
                    //boing.play();
                    count++;
                }
                if (left.touches(ball) || right.touches(ball)){
                    ball.bounceHorizontal();
                    //boing.play();
                    count++;
                }
        }
        else {//restart button pressed
              frame=0;
              if (timer.isRunning()) {
                     timer.stop();
                  myButton.setLabel("Start");
                  ball.setVisable(false);
                  count=0;
               } else {
                   timer.start();
                   myButton.setLabel("Stop");
                   ball=new Ball(10);
                   ball.setVisable(true);
                   //boing.play();  
               }                 
        }
        repaint();
    }
}
</code>

[[https://mathorama.com/apcs/uploads/Main/boing.wav|bounce.wav]]