A202/A598 and A290/A590 CGI/PHP and Java (Fall 2009)

Fall Semester 2009

Lecture 11/03: Running Java Programs. Getting ready for Homework One. .

One of the books I recommended is:

Java All-In-One Desk Reference For Dummies, 2nd Edition
by Doug Lowe and Barry Burd

The book is available from the on-line resource:

http://www.libraries.iub.edu/scripts/countResources.php?resourceId=59555

Here's some help with what you can learn from this book.

Please compile and run all these programs today.

For each program describe in a few sentences what the program does (and how it accomplishes that).

You can use the book of course.

What I need from you:

an e-mail later in the week when you're done running all these programs below

Book Six: Swing

Swinging into Swing

The key is to know your building blocks.

The rest is really useful and informative to read.

More programs to look at:

http://www.cs.indiana.edu/classes/a202-dger/spr2006/notes/One.html
http://www.cs.indiana.edu/classes/a202-dger/spr2006/notes/Two.html
http://www.cs.indiana.edu/classes/a202-dger/spr2006/notes/Three.html
http://www.cs.indiana.edu/classes/a202-dger/spr2006/notes/Four.html
http://www.cs.indiana.edu/classes/a202-dger/spr2006/notes/labTwo.html
http://www.cs.indiana.edu/classes/a202-dger/spr2006/notes/Five.html
http://www.cs.indiana.edu/classes/a202-dger/spr2006/notes/Six.html

Handling Events
This is something we have seen already. Same, redesigned (to be posted here).
Getting Input from the User
This has also appeared before. There's more in the chapter, in snippets.
Here's a second program though. There's a slider program at
```
http://www.cs.indiana.edu/classes/a202-dger/sum2009/ekeif/mon0720.html
```
It can now be reverse-engineered
Choosing from a List
Useful information, no program selected to look at. But a good reference chapter.
Using Layout Managers
Just think of layout managers as objects that will try to keep your GUI widgets together, as specified by you.

Book Seven: Web Programming

Creating Applets

import javax.swing.*;
import java.awt.event.*;
import javax.swing.border.*;

public class PizzaApplet extends JApplet                 
{
      private JButton buttonOK;
      private JRadioButton small, medium, large;

      private JCheckBox pepperoni, mushrooms, anchovies;

      public void init()                                 
      {
          this.setSize(320,200);                             
          ButtonListener bl = new ButtonListener();

          JPanel mainPanel = new JPanel();
 
          JPanel sizePanel = new JPanel();
          Border b1 = BorderFactory.createTitledBorder("Size");
          sizePanel.setBorder(b1);

          ButtonGroup sizeGroup = new ButtonGroup();
          small = new JRadioButton("Small");
          small.setSelected(true);

          sizePanel.add(small);
          sizeGroup.add(small);

          medium = new JRadioButton("Medium");
          sizePanel.add(medium);
          sizeGroup.add(medium);

          large = new JRadioButton("Large");
          sizePanel.add(large);
          sizeGroup.add(large);

          mainPanel.add(sizePanel);
  
          JPanel topPanel = new JPanel();
          Border b2 = BorderFactory.createTitledBorder("Toppings");
          topPanel.setBorder(b2);

          pepperoni = new JCheckBox("Pepperoni");
          topPanel.add(pepperoni);

          mushrooms = new JCheckBox("Mushrooms");
          topPanel.add(mushrooms);

          anchovies = new JCheckBox("Anchovies");
          topPanel.add(anchovies);

          mainPanel.add(topPanel);

          buttonOK = new JButton("OK");
          buttonOK.addActionListener(bl);
          mainPanel.add(buttonOK);

          this.add(mainPanel);

          this.setVisible(true);
      }

      private class ButtonListener implements ActionListener
      {
          public void actionPerformed(ActionEvent e)
          {
              if (e.getSource() == buttonOK)
              {
                  String tops = "";
                  if (pepperoni.isSelected()) tops += "Pepperoni\n";
                  if (mushrooms.isSelected()) tops += "Mushrooms\n";

                  if (anchovies.isSelected()) tops += "Anchovies\n";

                  String msg = "You ordered a ";
                  if (small.isSelected()) msg += "small pizza with ";
                  if (medium.isSelected()) msg += "medium pizza with ";
                  if (large.isSelected()) msg += "large pizza with ";

                  if (tops.equals("")) msg += "no toppings.";
                  else msg += "the following toppings:\n" + tops;
                  JOptionPane.showMessageDialog(buttonOK, msg, "Your Order", JOptionPane.INFORMATION_MESSAGE);

                  pepperoni.setSelected(false);
                  mushrooms.setSelected(false);
                  anchovies.setSelected(false);
                  small.setSelected(true);
              }
          }
      }
}

It comes with an HTML file:

<html>
    <head>
        <title>The Pizza Applet</title>
    </head>
    <body>
        <H1>Welcome to the Pizza Applet!</H1>

        <APPLET code="PizzaApplet" width="300" height="180">
            Sorry, your browser isn't able to run Java applets.
        </APPLET>
    </body>
</html>

Creating Servlets

We've installed Tomcat, and have started discussing JSPs and servlets.

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;

public class HelloWorld extends HttpServlet
{
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<html>");
        out.println("<head>");
        out.println("<title>HelloWorld</title>");
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>Hello, World!</h1>");
        out.println("</body>");
        out.println("</html>");
    }
}

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;

public class HelloServlet extends HttpServlet
{
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        String msg = getGreeting();
        out.println("<html>");
        out.println("<head>");
        out.println("<title>HelloWorld Servlet</title>");
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>");
        out.println(msg);
        out.println("</h1>");
        out.println("</body>");
        out.println("</html>");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
    {
        doGet(request, response);
    }

    private String getGreeting()
    {
        String msg = "";
        int rand = (int)(Math.random() * (6)) + 1;
        switch (rand)
        {
            case 1:
                return "Hello, World!";
            case 2:
                return "Greetings!";

            case 3:
                return "Felicitations!";
            case 4:
                return "Yo, Dude!";
            case 5:
                return "Whasssuuuup?";
            case 6:
                return "Hark!";
        }
        return null;
    }
}

We need to talk about deploying too (webapps, contexts, web.xml and so on).

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class InputServlet extends HttpServlet
{
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
    {
        String name = request.getParameter("Name");

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        out.println("<html>");
        out.println("<head>");
        out.println("<title>Input Servlet</title>");
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>");
        out.println("Hello " + name);
        out.println("</h1>");
        out.println("</body>");
        out.println("</html>");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
    {
        doGet(request, response);
    }
}

Pass the input to the above via the URL or an HTML form.

Using Java Server Pages

Good, well-written descriptions of what you need to know.

<html>
    <%@ page import="java.text.*" %>
    <%@ page import="java.util.*" %>
    <head>

        <title>Date JSP</title>
    </head>
    <body>
    <h1>
      Today is
      <%
          DateFormat df = DateFormat.getDateInstance(DateFormat.FULL);
          Date today = new Date();
          String msg = df.format(today);
          out.println(msg);
      %>

    </h1>
    <h1>Have a nice day!</h1>
    </body>
</html>

This is like PHP:

<html>

    <head>
    <title>Can't
    </head>
    <body>
    <% for (int i = 0; i < 12; i++)
       {
    %>
    All work and no play makes Jack a dull boy.<br>

    <%
       }
    %>
    </body>
</html>

Using JavaBeans
Skip this chapter.

Book Eight: Files and Databases

Working with Files

This is a traditionally useful chapter. Quick program to look at:

import java.io.*;

public class ListDirectory
{
    public static void main(String[] args)
    {
        String path = args[0];
        File dir = new File(path);
        if (dir.isDirectory())
        {
            File[] files = dir.listFiles();
            for (File f : files)
            {
                System.out.println(f.getName());
            }
        }
        else
            System.out.println("Not a directory.");
    }
}

Using File Streams

import java.io.*;                                        
import java.text.NumberFormat;

public class ReadFile
{
    public static void main(String[] args)
    {
        NumberFormat cf = NumberFormat.getCurrencyInstance();

        BufferedReader in = getReader("movies.txt");    
        Movie movie = readMovie(in);                    
        while (movie != null)                           
        {
            String msg = Integer.toString(movie.year);
            msg += ": " + movie.title;
            msg += " (" + cf.format(movie.price) + ")";
            System.out.println(msg);
            movie = readMovie(in);
        }
    }                                                    
    private static BufferedReader getReader(String name)
    {
        BufferedReader in = null;
        try
        {
            File file = new File(name);
            in = new BufferedReader(
                new FileReader(file) );
        } 
    catch (FileNotFoundException e)
    {
        System.out.println("The file doesn't exist.");
        System.exit(0);
    }
    catch (IOException e)
    {
        System.out.println("I/O Error");
        System.exit(0);
    }
    return in;
}

private static Movie readMovie(BufferedReader in)    
{
    String title;
    int year;
    double price;
    String line = "";
    String[] data;

    try
    {
        line = in.readLine();
    }
    catch (IOException e)
    {
        System.out.println("I/O Error");
        System.exit(0);
    }

    if (line == null)
        return null;
    else
    {
        data = line.split("\t");
        title = data[0];
        year = Integer.parseInt(data[1]);
        price = Double.parseDouble(data[2]);
        return new Movie(title, year, price);
    }
}

private static class Movie                           
{
    public String title;
    public int year;
    public double price;

    public Movie(String title, int year, double price)
    { 
            this.title = title;
            this.year = year;
            this.price = price;
        }
    }
}

This needs the following file (movies.txt):

It's a Wonderful Life [tab]  from book1946 [tab]  from book14.95
The Great Race [tab]  from book1965 [tab]  from book12.95
Young Frankenstein [tab]  from book1974 [tab]  from book16.95
The Return of the Pink Panther [tab]  from book1975.11.95
Star Wars [tab]  from book1977 [tab]  from book17.95
The Princess Bride [tab]  from book1987 [tab]  from book16.95
Glory [tab]  from book1989 [tab]  from book14.95
Apollo 13 [tab]  from book1995 [tab]  from book19.95
The Game [tab]  from book1997 [tab]  from book14.95
The Lord of the Rings: The Fellowship of the Ring [tab]  from book2001 [tab]  from book19.95

By [tab] I am indicating the actual tab character.

There's much more to this chapter, but this will suffice for this review.

Database for $100, Please

This chapter is mostly about SQL and database design:

drop database movies;                                   
create database movies;                                  
use movies;                                              
create table movie (                                     
    id int not null auto_increment,                      
    title varchar(50),                                   
    year int,                                            
    price decimal(8,2),                                  
    primary key(id)                                      
);

insert into movie (title, year, price) values ("It's ...", ..., ...);

insert into movie (title, year, price) values ("The Great Race", 1965, 12.95);

insert into movie (title, year, price) values ("Young Frankenstein", 1974, 16.95);

insert into movie (title, year, price) values ("The Return of the Pink Panther", 1975, 11.95);

insert into movie (title, year, price) values ("Star Wars", 1977, 17.95);

insert into movie (title, year, price) values ("The Princess Bride", 1987, 16.95);

insert into movie (title, year, price) values ("Glory", 1989, 14.95);

insert into movie (title, year, price) values ("Apollo 13", 1995, 19.95);

insert into movie (title, year, price) values ("The Game", 1997, 14.95);

insert into movie (title, year, price) values ("The Lord of the Rings: The Fellowship of the Ring", 2001, 19.95);

Nothing else from this chapter will be highlighted here, but there's more you can benefit from if you read it.

Using JDBC to Connect to a Database
We'll have our own examples.
Working with XML
Skip this chapter, but know it's useful and interesting.

Book Nine: Fun and Games

Fun with Fonts and Colors

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

public class Fonts extends JFrame
{
    public static void main(String [] args)
    {
        new Fonts();
    }

    private JLabel sampleText;                                         
    private JComboBox fontComboBox;                                    
    private JComboBox sizeComboBox;
    private JCheckBox boldCheck, italCheck;

    private String[] fonts;                                            
    public Fonts()
    {
        this.setSize(500,150);
        this.setTitle("Fun with Fonts ");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        FontListener fl = new FontListener();                             
        sampleText = new JLabel(
            "All work and no play makes Jack a dull boy");
        this.add(sampleText, BorderLayout.NORTH);                         
        GraphicsEnvironment g;                                            
        g = GraphicsEnvironment
                .getLocalGraphicsEnvironment();
        fonts = g.getAvailableFontFamilyNames();

        JPanel controlPanel = new JPanel();                               
        fontComboBox = new JComboBox(fonts);                              
        fontComboBox.addActionListener(fl);
        controlPanel.add(new JLabel("Family: "));
        controlPanel.add(fontComboBox);

        Integer[] sizes = {7, 8, 9, 10, 11, 12,                           
                           14, 18, 20, 22, 24, 36};

        sizeComboBox = new JComboBox(sizes);
        sizeComboBox.setSelectedIndex(5);
        sizeComboBox.addActionListener(fl);
        controlPanel.add(new JLabel("Size: "));
        controlPanel.add(sizeComboBox);

        boldCheck = new JCheckBox("Bold");                           
        boldCheck.addActionListener(fl);
        controlPanel.add(boldCheck);

        italCheck = new JCheckBox("Ital");                           
        italCheck.addActionListener(fl);
        controlPanel.add(italCheck);

        this.add(controlPanel, BorderLayout.SOUTH);                  
        fl.updateText();

        this.setVisible(true);
    }

    private class FontListener implements ActionListener
    {
        public void actionPerformed(ActionEvent e)
        {
           updateText();                                             
        }

        public void updateText()                                     
        {
           String name = (String) fontComboBox.getSelectedItem();

           Integer size = (Integer)sizeComboBox.getSelectedItem();

           int style;
           if (   boldCheck.isSelected()
               && italCheck.isSelected())
               style = Font.BOLD | Font.ITALIC;
           else if (boldCheck.isSelected())
               style = Font.BOLD;
           else if (italCheck.isSelected())
               style = Font.ITALIC;
           else
               style = Font.PLAIN;

           Font f = new Font(name, style,
               size.intValue());
           sampleText.setFont(f);
        }
    }
}

Can you walk [through] the code above?

Hopefully that's not too hard.

There's more in the chapter.

Drawing Shapes

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.awt.geom.*;
import java.util.*;

public class DrawingBoard extends JFrame

{

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

    public DrawingBoard()                                              
    {
        this.setSize(300, 300);
        this.setTitle("The Drawing Board");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.add(new PaintSurface(), BorderLayout.CENTER);
        this.setVisible(true);
    }

    private class PaintSurface extends JComponent
    {
        ArrayList<Shape> shapes = new ArrayList<Shape>();                 
        Point startDrag, endDrag;

        public PaintSurface()
        {
            this.addMouseListener(new MouseAdapter()
              {
                public void mousePressed(MouseEvent e)                    
                {
                    startDrag = new Point(e.getX(), e.getY());
                    endDrag = startDrag;
                    repaint();
                }

                public void mouseReleased(MouseEvent e)                   
                {
                    Shape r = makeRectangle(
                                 startDrag.x, startDrag.y,
                                 e.getX(), e.getY());
                    shapes.add(r);
                    startDrag = null;
                    endDrag = null;
                    repaint();
                }
              } );

            this.addMouseMotionListener(new MouseMotionAdapter()
              {
                public void mouseDragged(MouseEvent e)                    
                {
                    endDrag = new Point(e.getX(), e.getY());
                    repaint();
                }
              } );
        }

        public void paint(Graphics g)                                     
        {
            Graphics2D g2 = (Graphics2D)g;

            // turn on antialiasing

            g2.setRenderingHint(
                RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);

            // draw background grid
            g2.setPaint(Color.LIGHT_GRAY);
            for (int i = 0; i < getSize().width; i += 10)
            {
                Shape line = new Line2D.Float(
                    i, 0, i, getSize().height);
                g2.draw(line);
            }

            for (int i = 0; i < getSize().height; i += 10)
            {
                Shape line = new Line2D.Float(
                    0, i, getSize().width, i);
                g2.draw(line);
            }

            // draw the shapes
            Color[] colors = {Color.RED, Color.BLUE,                      
                             Color.PINK, Color.YELLOW,
                             Color.MAGENTA, Color.CYAN };
            int colorIndex = 0;

            g2.setStroke(new BasicStroke(2));                             
            g2.setComposite(AlphaComposite.getInstance(
                AlphaComposite.SRC_OVER, 0.50f));

            for (Shape s : shapes)                                        
            {
                g2.setPaint(Color.BLACK);
                g2.draw(s);
                g2.setPaint(colors[(colorIndex++)%6]);
                g2.fill(s);
            }

            // paint the temporary rectangle
            if (startDrag != null && endDrag != null)                    
            {
                g2.setPaint(Color.LIGHT_GRAY);
                Shape r = makeRectangle(
                    startDrag.x, startDrag.y,
                    endDrag.x, endDrag.y);
                g2.draw(r);
            }
        }

        private Rectangle2D.Float makeRectangle(                        
            int x1, int y1, int x2, int y2)
        {
            int x = Math.min(x1, x2);
            int y = Math.min(y1, y2);
            int width = Math.abs(x1 - x2);
            int height = Math.abs(y1 - y2);
            return new Rectangle2D.Float(
                x, y, width, height);
        }
    }
}

This is not very surprising.

Using Images and Sound

import javax.swing.*;

public class PictureApp extends JFrame
{
    public static void main(String [] args)
    {
        new PictureApp();
    }

    public PictureApp()
    {
        this.setTitle("Picture Application");
        this.setDefaultCloseOperation(
            JFrame.EXIT_ON_CLOSE);
        JPanel panel1 = new JPanel();
        ImageIcon pic = new ImageIcon("HalfDome.jpg");
        panel1.add(new JLabel(pic));
        this.add(panel1);
        this.pack();
        this.setVisible(true);
    }
}

Get your own picture. 

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.io.*;

public class PictureFrame extends JFrame
    implements ActionListener
{
    Image img;                                                          
    JButton getPictureButton;

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

    public PictureFrame()
    {
        this.setSize(300, 300);
        this.setTitle("Picture Frame Application");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel picPanel = new PicturePanel();                             
        this.add(picPanel, BorderLayout.CENTER);

        JPanel buttonPanel = new JPanel();                                
        getPictureButton = new JButton("Get Picture");
        getPictureButton.addActionListener(this);
        buttonPanel.add(getPictureButton);
        this.add(buttonPanel, BorderLayout.SOUTH);

        this.setVisible(true);
    }

    public void actionPerformed(ActionEvent e)                         
    {
        String file = getImageFile();
        if (file != null)
        {
            Toolkit kit = Toolkit.getDefaultToolkit();
            img = kit.getImage(file);
            img = img.getScaledInstance(
                300, -1, Image.SCALE_SMOOTH);
            this.repaint();
        }
    }

    private String getImageFile()                                      
    {
        JFileChooser fc = new JFileChooser();
        fc.setFileFilter(new ImageFilter());
        int result = fc.showOpenDialog(null);
        File file = null;
        if (result == JFileChooser.APPROVE_OPTION)
        {
            file = fc.getSelectedFile();
            return file.getPath();
        }
        else
            return null;

    }
    private class PicturePanel extends JPanel                          
    {
        public void paint(Graphics g)
        {
            g.drawImage(img, 0, 0, this);
        }
    }
    private class ImageFilter                                          
        extends javax.swing.filechooser.FileFilter
    {
        public boolean accept(File f)
        {
            if (f.isDirectory())
                return true;
            String name = f.getName();
            if (name.matches(".*((.jpg)|(.gif)|(.png))"))
                return true;
            else
                return false;
        }

        public String getDescription()
        {
            return "Image files (*.jpg, *.gif, *.png)";
        }
    }
}

A more evolved picture browser...

(I'm skipping sound for now).

Animation and Game Programming

/* <applet code=NotPong.class width=300 height=300>

   </applet>
 */

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.geom.*;
import java.util.concurrent.*;

public class NotPong extends JApplet                                       
{
    public static final int WIDTH = 400;
    public static final int HEIGHT = 400;

    private PaintSurface canvas;

    public void init()                                                 
    {
        this.setSize(WIDTH, HEIGHT);
        canvas = new PaintSurface();
        this.add(canvas, BorderLayout.CENTER);
        ScheduledThreadPoolExecutor executor =
            new ScheduledThreadPoolExecutor(3);
        executor.scheduleAtFixedRate(new AnimationThread(this),
            0L, 20L, TimeUnit.MILLISECONDS);
    }
}

class AnimationThread implements Runnable                                
{
    JApplet c;

    public AnimationThread(JApplet c)
    {
        this.c = c;

    }

    public void run()
    {
        c.repaint();
    }
}

class PaintSurface extends JComponent                                     
{
    int paddle_x = 0;                                                 
    int paddle_y = 360;

    int score = 0;                                                     
    float english = 1.0f;

    Ball ball;                                                         
    Color[] color = {Color.RED, Color.ORANGE,                         
                     Color.MAGENTA, Color.ORANGE,
                     Color.CYAN, Color.BLUE};
    int colorIndex;

    public PaintSurface()                                              
    {
        addMouseMotionListener(new MouseMotionAdapter()
            {
                public void mouseMoved(MouseEvent e)
                {
                    if (e.getX() - 30 - paddle_x > 5)
                        english = 1.5f;
                    else if (e.getX() - 30 - paddle_x < -5)
                        english = -1.5f;
                    else
                        english = 1.0f;
                    paddle_x = e.getX() - 30;
                }
            } );
        ball = new Ball(20);
    }

    public void paint(Graphics g)                                       
    {
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(
            RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
        Shape paddle = new Rectangle2D.Float(                              
            paddle_x, paddle_y, 60, 8);

        g2.setColor(color[colorIndex % 6]);                                
        if (ball.intersects(paddle_x, paddle_y, 60, 8)                     
            && ball.y_speed > 0)
        {
            ball.y_speed = -ball.y_speed;
            ball.x_speed = (int)(ball.x_speed * english);
            if (english != 1.0f)
                colorIndex++;
            score += Math.abs(ball.x_speed * 10);

        }

        if (ball.getY() + ball.getHeight()                            
           >= NotPong.HEIGHT)
        {
           ball = new Ball(20);
           score -= 1000;
           colorIndex = 0;
        }
        ball.move();                                                 
        g2.fill(ball);

        g2.setColor(Color.BLACK);                                    
        g2.fill(paddle);
        g2.drawString("Score: " + score, 250, 20);                   
    }
}

class Ball extends Ellipse2D.Float                                   
{
    public int x_speed, y_speed;
    private int d;
    private int width = NotPong.WIDTH;
    private int height = NotPong.HEIGHT;

    public Ball(int diameter)
    {
        super((int)(Math.random() * (NotPong.WIDTH - 20) + 1),
              0, diameter, diameter);
        this.d = diameter;
        this.x_speed = (int)(Math.random() * 5 + 5);
        this.y_speed = (int)(Math.random() * 5 + 5);
    }

    public void move()
    {
        if (super.x < 0 || super.x > width - d)
            x_speed = -x_speed;
        if (super.y < 0 || super.y > height - d)
            y_speed = -y_speed;
        super.x += x_speed;
        super.y += y_speed;
    }
}

That's it.