Using the Full-Screen Exclusive Mode API in Java

Figure 1

Figure 2

Figure 3

public class FullScreen01 extends JFrame 
                                 implements ActionListener{

  private GraphicsDevice graphicsDevice;
  private DisplayMode origDisplayMode;
  private JButton exitButton = new JButton(
                                  "Exit Full-Screen Mode");

Listing 1

  public static void main(String[] args){

    GraphicsEnvironment graphicsEnvironment = 
         GraphicsEnvironment.getLocalGraphicsEnvironment();

    GraphicsDevice[] devices = 
                    graphicsEnvironment.getScreenDevices();

    for(int cnt = 0;cnt < 1;cnt++){
      System.out.println(devices[cnt]);
    }//end for loop

Listing 2

    new FullScreen01(devices[0]);
  }//end main

Listing 3

  public FullScreen01(GraphicsDevice graphicsDevice){

    this.graphicsDevice = graphicsDevice;

Listing 4

    setTitle("This title will be hidden (undecorated)");


Listing 5

    origDisplayMode = graphicsDevice.getDisplayMode();

Listing 6

    exitButton.addActionListener(this);
    
    getContentPane().add(exitButton, BorderLayout.NORTH);

Listing 7

    //Place four labels in the JFrame solely for the
    // purpose of showing that it is a full-screen
    // undecorated JFrame.
    JLabel eastLabel = new JLabel("     East     ");
    eastLabel.setOpaque(true);
    eastLabel.setBackground(Color.RED);
    getContentPane().add(eastLabel,BorderLayout.EAST);
    
    JLabel southLabel = 
                 new JLabel("South",SwingConstants.CENTER);
    southLabel.setOpaque(true);
    southLabel.setBackground(Color.GREEN);
    getContentPane().add(southLabel,BorderLayout.SOUTH);
    
    JLabel westLabel = new JLabel("     West     ");
    westLabel.setOpaque(true);
    westLabel.setBackground(Color.RED);
    getContentPane().add(westLabel,BorderLayout.WEST);
    
    JLabel centerLabel = 
                new JLabel("Center",SwingConstants.CENTER);
    centerLabel.setOpaque(true);
    centerLabel.setBackground(Color.WHITE);
    getContentPane().add(centerLabel,BorderLayout.CENTER);

Listing 8

    if (graphicsDevice.isFullScreenSupported()){
      // Enter full-screen mode with an undecorated,
      // non-resizable JFrame object.
      setUndecorated(true);
      setResizable(false);
      //Make it happen!
      graphicsDevice.setFullScreenWindow(this);
      validate();
    }else{
      System.out.println("Full-screen mode not supported");
    }//end else    

  }//end constructor

Listing 9

  public void actionPerformed(ActionEvent evt){
    //Restore the original display mode
    graphicsDevice.setDisplayMode(origDisplayMode);
    //Terminate the program
    System.exit(0);
  }//end actionPerformed
}//end class

Listing 10

class FullScreen02 extends JFrame 
                                 implements ActionListener{

  //Code deleted for brevity.
  
  public static void main(String[] args){
    //Code deleted for brevity.
  }//end main

Listing 11

  public FullScreen02(GraphicsDevice graphicsDevice){

    //Code deleted for brevity.
    
    getContentPane().add(new AnimationPanel());

    //Code deleted for brevity.    

  }//end constructor

Listing 12

  public void actionPerformed(ActionEvent evt){
    //Code deleted for brevity.
  }//end actionPerformed

}//end class FullScreen02

Listing 13

class BackgroundImage{
  //Code deleted for brevity.
}//end class BackgroundImage

Listing 14

class SpriteManager{
  private ArrayList <Sprite> theSprites = 
                                   new ArrayList<Sprite>();
    //Code deleted for brevity.
}//end class SpriteManager

Listing 15

class Sprite{
  //Code deleted for brevity.
  private ArrayList <History> tailData = 
                                  new ArrayList<History>();

  //Code deleted for brevity.

  public void drawSpriteImage(Graphics g){
    //Code deleted for brevity.
    Iterator <History> iterator = tailData.iterator();
    //Code deleted for brevity.
  }//end drawSpriteImage()

  //Code deleted for brevity.

}//end Sprite class

Listing 16

class History{
  //Code deleted for brevity.
}//end class History

Listing 17

class AnimationPanel extends JPanel implements Runnable{

    //Code deleted for brevity.

  private int animationDelay = 83;
  private javax.swing.Timer animationTimer;

Listing 18

  public AnimationPanel(){//constructor
    // Load and track the images
    mediaTracker = new MediaTracker(this);
    
    //Get and track the background image.
    backGroundImage = Toolkit.getDefaultToolkit().
                              getImage("background03.gif");

Listing 19

    animationTimer = new javax.swing.Timer(animationDelay,
      new ActionListener(){
        public void actionPerformed(ActionEvent e){
          //Update the sprites
          spriteManager.updateSprites();
          //Update the animation panel on the screen
          activeRenderer(getGraphics());
        }//end actionPerformed
      }//end new ActionListener
    );//end new javax.swing.Timer

  }//end constructor

Listing 20

  private void activeRenderer(Graphics g){
    //Create the offscreen graphics context
    if(offScreenGraphicsCtx == null){
      offScreenImage = 
             createImage(getSize().width,getSize().height);
      offScreenGraphicsCtx = offScreenImage.getGraphics();
    }//end if

    // Draw the sprites offscreen
    spriteManager.drawScene(offScreenGraphicsCtx);

    // Draw the scene onto the screen
    if(offScreenImage != null){
      g.drawImage(offScreenImage,0,0,this);
    }//end if

  }//end activeRenderer method

Listing 21

  private Sprite makeSprite(Point position,int imageIndex){
    //Code deleted for brevity.
  }//end makeSprite()

Listing 22

  public void run(){
    while(getWidth() == 0){
      System.out.print(".");
    }//end while loop
    while(getHeight() == 0){
      System.out.print(".");
    }//end while loop

Listing 23

    spriteManager = new SpriteManager(
                 new BackgroundImage(this,backGroundImage),
                 getWidth(),
                 getHeight());

    //Create 200 sprites from 6 gif files.
    for(int cnt = 0;cnt < 200;cnt++){
      Point position = 
                 spriteManager.getEmptyPosition(
                 new Dimension(gifImages[0].getWidth(this),
                 gifImages[0].getHeight(this)));
      spriteManager.addSprite(
                             makeSprite(position,cnt % 6));
    }//end for loop

Listing 24

    animationTimer.start();//Start the animation timer

  }//end run method

}//end AnimationPanel class

Listing 25

/*FullScreen01.java
This is a skeleton program that implements the
Full-Screen Exclusive Mode

The program places an undecorated non-resizable JFrame
object on the screen in the Full-Screen Exclusive Mode.

A JButton appears in the North location of the JFrame.
Clicking the button causes the program to exit the full-
screen mode, restore the original graphics mode, and
terminate.

The program places red, green, and white JLabels in the
East, West, South, and Center locations solely to 
demonstrate that the graphics object is an undecorated
non-resizable JFrame object.

The program displays a list of the available graphics 
devices solely for information purposes in the command-
line window.  However, that window is hidden behind the
full-screen version of the JFrame object and isn't visible
until the full-screen mode is terminated.

Even though the program displays a list of all of the
graphics devices, it operates only on the first graphics 
device in the list.

Tested using J2SE5.0 under WinXP.  J2SE 1.4 or later is
required for the setFullScreenWindow method of the
GraphicsDevice object.
**********************************************************/

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

public class FullScreen01 extends JFrame 
                                 implements ActionListener{

  private GraphicsDevice graphicsDevice;
  private DisplayMode origDisplayMode;
  private JButton exitButton = new JButton(
                                  "Exit Full-Screen Mode");
  
  public static void main(String[] args){
    //Get and display a list of graphics devices solely for
    // information purposes.
    GraphicsEnvironment graphicsEnvironment = 
         GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice[] devices = 
                    graphicsEnvironment.getScreenDevices();
    for(int cnt = 0;cnt < 1;cnt++){
      System.out.println(devices[cnt]);
    }//end for loop
    
    //Construct a full-screen object using
    // graphicsDevice 0.
    new FullScreen01(devices[0]);
  }//end main

  //Constructor
  public FullScreen01(GraphicsDevice graphicsDevice){
    //Save a reference to the graphics device as an
    // instance variable so that it can be used later to
    // exit the full-screen mode.
    this.graphicsDevice = graphicsDevice;
    
    setTitle("This title will be hidden (undecorated)");
    
    //Get and save a reference to the original display
    // mode as an instance variable so that it can be
    // restored later.
    origDisplayMode = graphicsDevice.getDisplayMode();
    
    //Register an action listener on the exitButton.
    exitButton.addActionListener(this);
    
    //Place the exitButton in the JFrame    
    getContentPane().add(exitButton, BorderLayout.NORTH);
    
    //Place four labels in the JFrame solely for the
    // purpose of showing that it is a full-screen
    // undecorated JFrame.
    JLabel eastLabel = new JLabel("     East     ");
    eastLabel.setOpaque(true);
    eastLabel.setBackground(Color.RED);
    getContentPane().add(eastLabel,BorderLayout.EAST);
    
    JLabel southLabel = 
                 new JLabel("South",SwingConstants.CENTER);
    southLabel.setOpaque(true);
    southLabel.setBackground(Color.GREEN);
    getContentPane().add(southLabel,BorderLayout.SOUTH);
    
    JLabel westLabel = new JLabel("     West     ");
    westLabel.setOpaque(true);
    westLabel.setBackground(Color.RED);
    getContentPane().add(westLabel,BorderLayout.WEST);
    
    JLabel centerLabel = 
                new JLabel("Center",SwingConstants.CENTER);
    centerLabel.setOpaque(true);
    centerLabel.setBackground(Color.WHITE);
    getContentPane().add(centerLabel,BorderLayout.CENTER);

    if (graphicsDevice.isFullScreenSupported()){
      // Enter full-screen mode witn an undecorated,
      // non-resizable JFrame object.
      setUndecorated(true);
      setResizable(false);
      //Make it happen!
      graphicsDevice.setFullScreenWindow(this);
      validate();
    }else{
      System.out.println("Full-screen mode not supported");
    }//end else    

  }//end constructor

  //The following method is invoked when the used clicks
  // the exitButton
  public void actionPerformed(ActionEvent evt){
    //Restore the original display mode
    graphicsDevice.setDisplayMode(origDisplayMode);
    //Terminate the program
    System.exit(0);
  }//end actionPerformed
}//end class

Listing 26

/*FullScreen02.java
Copyright 2006, R.G.Baldwin

The purpose of this program is to demonstrate the use of
the Full-Screen Exclusive Mode API for simulation and
animation.

This program is an update to the earlier program named
Animate03 as described in the earlier lesson number 
Java1466.  This program has been modernized to
make use of the Swing Timer class as an animation timer,
and also to use Active Rendering (as opposed to Passive
Rendering) in Full-Screen Exclusive Mode.  It has also been
modernized to use generics.

The program animates colored worms on a background image
in Full-Screen Exclusive mode.  See the discussion of
Active Rendering versus Passive Rendering in The Java
Tutorial at:

http://java.sun.com/docs/books/tutorial/extra/fullscreen/
index.html

Using Active Rendering, the program does not call the 
repaint method to ask the operating system to call the 
update method.  Rather, the program invokes a method named 
activeRenderer, which draws the animated sprites on the 
screen without concern for sharing the screen with other
applications.  (There are no other applications on the
screen in full-screen mode.)

The program places an undecorated non-resizable JFrame
object on the screen in Full-Screen Exclusive Mode.

A JButton appears in the North location of the JFrame.
Clicking the button causes the program to exit the full-
screen mode, restore the original graphics mode, and
terminate.

A JPanel appears in the center of the JFrame object.
The colored worms are animated as sprites on the JPanel.
A background image is drawn on the JPanel at the beginning
of each animation cycle.  This image erases the sprites
that were previously there creating a clean slate for 
drawing the sprites in their new positions.  If the
background image is eliminated, the worms turn into long
tubes because the old sprite images are never erased.

The background image that is used fits a 1024 x 768
screen in Full-Screen Exclusive mode.  If the screen is
a different size, a different size background image is
needed.

Tested using J2SE5.0 under WinXP.  J2SE 1.4 or later is
required for the setFullScreenWindow method of the
GraphicsDevice object.  J2SE 5.0 or later is required
to support generics.
**********************************************************/

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

class FullScreen02 extends JFrame 
                                 implements ActionListener{

  private GraphicsDevice graphicsDevice;
  private DisplayMode origDisplayMode;
  private JButton exitButton = new JButton(
     "Exit Full-Screen Mode  Copyright 2006, R.G.Baldwin");
  
  public static void main(String[] args){
    //Get a list of available graphics devices.
    GraphicsEnvironment graphicsEnvironment = 
         GraphicsEnvironment.getLocalGraphicsEnvironment();
    GraphicsDevice[] devices = 
                    graphicsEnvironment.getScreenDevices();
    
    //Construct a full-screen object using the first
    // graphics device in the array.  Ignore the others, if
    // there are any.
    new FullScreen02(devices[0]);
  }//end main
  //-----------------------------------------------------//

  //Constructor
  public FullScreen02(GraphicsDevice graphicsDevice){
    //Save a reference to the graphics device as an
    // instance variable so that it can be used later to
    // exit the full-screen mode.
    this.graphicsDevice = graphicsDevice;
    
    setTitle("This title will be hidden (undecorated)");
    
    //Get and save a reference to the original display
    // mode as an instance variable so that it can be
    // restored later.
    origDisplayMode = graphicsDevice.getDisplayMode();
    
    //Register an action listener on the exitButton.
    exitButton.addActionListener(this);
    
    //Place the exitButton at the top of the JFrame    
    getContentPane().add(exitButton,BorderLayout.NORTH);
    
    //Create an animation panel and place it in the center
    // of the JFrame.
    getContentPane().add(new AnimationPanel());

    if(graphicsDevice.isFullScreenSupported()){
      // Enter full-screen mode witn an undecorated,
      // non-resizable JFrame object.
      setUndecorated(true);
      setResizable(false);
      graphicsDevice.setFullScreenWindow(this);
      validate();
    }else{
      System.out.println("Full-screen mode not supported");
    }//end else    

  }//end constructor
  //-----------------------------------------------------//

  //The following method is invoked when the used clicks
  // the exitButton
  public void actionPerformed(ActionEvent evt){
    //Restore the original display mode
    graphicsDevice.setDisplayMode(origDisplayMode);
    //Terminate the program
    System.exit(0);
  }//end actionPerformed
  //-----------------------------------------------------//
}//end class FullScreen02
//=======================================================//

//This is a convenience class that makes it a little
// easier to deal with the background image.  Note that
// much of the impetus for this class went away when the
// animation program named Animate 03 was converted to
// full-screen mode. Several convenience methods having to
// do with the size of the background image were eliminated
// at that time.
class BackgroundImage{
  private Image image;
  private Component component;

  public BackgroundImage(Component component,Image image){
    this.component = component;
    this.image = image;
  }//end construtor

  public void drawBackgroundImage(Graphics g){
    //Note that component is an ImageObserver in the
    // following statement.
    g.drawImage(image,0,0,component);
  }//end drawBackgroundImage()
}//end class BackgroundImage
//=======================================================//

//An object of this class manages a collection of animated
// sprites stored in an ArrayList object.  (A Vector
// object was used in the earlier version named Animate03.)
// Note that this class also underwent some modernization
// with respect to the use of generics as released in
// J2SE 5.0. 
class SpriteManager{
  private ArrayList <Sprite> theSprites = 
                                   new ArrayList<Sprite>();
  private BackgroundImage backgroundImage;
  private int panelWidth;
  private int panelHeight;
  //-----------------------------------------------------//
  
  public SpriteManager(BackgroundImage backgroundImage,
                       int panelWidth,
                       int panelHeight){
    this.backgroundImage = backgroundImage;
    this.panelWidth = panelWidth;
    this.panelHeight = panelHeight;
  }//end constructor
  //-----------------------------------------------------//
  
  public Point getEmptyPosition(Dimension spriteSize){
    Rectangle trialSpaceOccupied = new Rectangle(
                   0,0,spriteSize.width,spriteSize.height);
    Random rand = new Random(System.currentTimeMillis());
    boolean empty = false;
    int numTries = 0;

    //Search for an empty position.  If an empty position
    // can't be found after 100 tries, give up and allow
    // two sprites to occupy the same initial location.
    while(!empty && numTries++ < 100){
      // Get a trial position
      trialSpaceOccupied.x = Math.abs(
                              rand.nextInt() % panelWidth);
      trialSpaceOccupied.y = Math.abs(
                             rand.nextInt() % panelHeight);

      // Iterate through existing sprites, checking if
      // position is empty
      boolean collision = false;
      for(int cnt = 0;cnt < theSprites.size();cnt++){
        Rectangle testSpaceOccupied = 
                    theSprites.get(cnt).getSpaceOccupied();

        if(trialSpaceOccupied.intersects(
                                       testSpaceOccupied)){
          collision = true;
        }//end if
      }//end for loop
      empty = !collision;
    }//end while loop
    
    return new Point(trialSpaceOccupied.x,
                                     trialSpaceOccupied.y);
  }//end getEmptyPosition()
  //-----------------------------------------------------//
  
  //This method updates the state information for each of
  // the sprites.
  public void updateSprites(){
    Sprite sprite;
    
    //Iterate through sprite list
    for(int cnt = 0;cnt < theSprites.size();cnt++){
      sprite = theSprites.get(cnt);
      //Update a sprite's position
      sprite.updatePosition();

      //Test for collision. Positive 
      // result indicates a collision
      int hitIndex = testForCollision(sprite);
      if(hitIndex >= 0){
        //A collision has occurred.  Make the two sprites
        // involved in the collision bounce off the other
        // sprite.
        bounceOffSprite(cnt,hitIndex);
      }//end if
    }//end for loop
  }//end updateSprites
  //-----------------------------------------------------//
  
  //This method tests for a collision between two sprites.
  private int testForCollision(Sprite testSprite){
    //Check for collision with other sprites
    Sprite  sprite;
    for(int cnt = 0;cnt < theSprites.size();cnt++){
      sprite = theSprites.get(cnt);
      if(sprite == testSprite)
        //Don't check self
        continue;
      //Invoke testCollision method of Sprite class to
      // perform the actual test.
      if(testSprite.testCollision(sprite))
        //Return index of colliding sprite
        return cnt;
    }//end for loop
    return -1;//No collision detected
  }//end testForCollision()
  //-----------------------------------------------------//
  
  private void bounceOffSprite(
                        int spriteAindex,int spriteBindex){
    //Swap motion vectors for bounce algorithm
    Sprite spriteA = theSprites.get(spriteAindex);
    Sprite spriteB = theSprites.get(spriteBindex);
    Point swap = spriteA.getMotionVector();
    spriteA.setMotionVector(spriteB.getMotionVector());
    spriteB.setMotionVector(swap);
  }//end bounceOffSprite()
  //-----------------------------------------------------//
  
  //This method draws the sprites in their new locations
  // on the animation panel.
  public void drawScene(Graphics g){
    //Draw the background and erase sprites from animation
    // panel.
    //Disable the following statement for an interesting
    // effect.  This will turn the short worms into tube
    // worms that increase in length forever.
    backgroundImage.drawBackgroundImage(g);

    //Iterate through sprites, drawing each sprite
    for(int cnt = 0;cnt < theSprites.size();cnt++)
      theSprites.get(cnt).drawSpriteImage(g);
  }//end drawScene()
  //-----------------------------------------------------//
  
  public void addSprite(Sprite sprite){
    //Add a new sprite to the ArrayList object.
    theSprites.add(sprite);
  }//end addSprite()
  //-----------------------------------------------------//
}//end class SpriteManager
//=======================================================//

//The class from which Sprite objects are instantiated.
class Sprite{
  private Component component;
  private Image[] image;
  private Rectangle spaceOccupied;
  private Point motionVector;
  private Rectangle bounds;
  private Random rand;
  private int frameNumber;
  //The following collection contains a reference to a
  // History object containing state information about
  // each spherical segment that makes up a worm.
  private ArrayList <History> tailData = 
                                  new ArrayList<History>();
  private int wormLength;
  //-----------------------------------------------------//
  
  //Constructor
  public Sprite(Component component,
                Image[] image,
                Point position,
                Point motionVector){
    //Seed a random number generator for this sprite with
    // the sprite position.
    rand = new Random(position.x);
    wormLength = Math.abs(rand.nextInt() % 20);
    this.component = component;
    this.image = image;
    this.spaceOccupied = new Rectangle(
                           position.x,
                           position.y,
                           image[0].getWidth(component),
                           image[0].getHeight(component));
    this.motionVector = motionVector;
    //Compute edges of usable graphics area.  Because we
    // are drawing on a JPanel, we don't need to worry
    // about insets for borders, banner, etc. This is much
    // simpler than in the earlier program named Animate03.
    bounds = new Rectangle(0,0,component.getSize().width,
                               component.getSize().height);
  }//end constructor
  //-----------------------------------------------------//
  
  public Rectangle getSpaceOccupied(){
    return spaceOccupied;
  }//end getSpaceOccupied()
  //-----------------------------------------------------//

  private void setSpaceOccupied(Point position){
    spaceOccupied.setLocation(position.x,position.y);
  }//setSpaceOccupied()
  //-----------------------------------------------------//

  public Point getMotionVector(){
    return motionVector;
  }//end getMotionVector()
  //-----------------------------------------------------//

  public void setMotionVector(Point motionVector){
    this.motionVector = motionVector;
  }//end setMotionVector()
  //-----------------------------------------------------//

  private void setBounds(Rectangle bounds){
    this.bounds = bounds;
  }//end setBounds()
  //-----------------------------------------------------//
  
  public void updatePosition(){
    Point position = new Point(
                          spaceOccupied.x,spaceOccupied.y);
    
    //Insert random behavior.  During each update, a sprite
    // has about one chance in 10 of making a small random
    // change to its motionVector.  When a change occurs,
    // the motionVector coordinate values are forced to
    // fall between -7 and 7.
    if(rand.nextInt() % 10 == 0){
      Point randomOffset = 
          new Point(rand.nextInt() % 3,rand.nextInt() % 3);
      motionVector.x += randomOffset.x;
      if(motionVector.x >= 7) 
        motionVector.x -= 7;
      if(motionVector.x <= -7) 
        motionVector.x += 7;
      motionVector.y += randomOffset.y;
      if(motionVector.y >= 7) 
        motionVector.y -= 7;
      if(motionVector.y <= -7) 
        motionVector.y += 7;
    }//end if

    //Make the move
    position.translate(motionVector.x,motionVector.y);

    //Bounce off the walls
    boolean bounceRequired = false;
    Point tempMotionVector = 
                  new Point(motionVector.x,motionVector.y);
    
    //Handle walls in x-dimension
    if(position.x < bounds.x){
      bounceRequired = true;
      position.x = bounds.x;
      //reverse direction in x
      tempMotionVector.x = -tempMotionVector.x;
    }else if((position.x + spaceOccupied.width) > 
                                (bounds.x + bounds.width)){
      bounceRequired = true;
      position.x = 
             bounds.x + bounds.width - spaceOccupied.width;
      //Reverse direction
      tempMotionVector.x = -tempMotionVector.x;
    }//end else if
    
    //Handle walls in y-dimension
    if(position.y < bounds.y){
      bounceRequired = true;
      position.y = bounds.y;
      tempMotionVector.y = -tempMotionVector.y;
    }else if((position.y + spaceOccupied.height) > 
                               (bounds.y + bounds.height)){
      bounceRequired = true;
      position.y = 
           bounds.y + bounds.height - spaceOccupied.height;
      tempMotionVector.y = -tempMotionVector.y;
    }//end else if
    
    //Save new motionVector
    if(bounceRequired) 
     setMotionVector(tempMotionVector);

    //Update spaceOccupied
    setSpaceOccupied(position);
  }//end updatePosition()
  //-----------------------------------------------------//

  //This method draws each worm, one segment at a time.
  // A new segment is added for the head each time this
  // method is called.  When the worm has reached its
  // specified length, the oldest segment is discarded 
  // each time this method is called.
  public void drawSpriteImage(Graphics g){
    frameNumber = Math.abs(rand.nextInt() % 6);
    //Add a new head to the worm.
    tailData.add(new History(
      image[frameNumber],spaceOccupied.x,spaceOccupied.y));
    Iterator <History> iterator = tailData.iterator();
    int cnt = 0;
    while(iterator.hasNext()){
      //Draw each segment of the worm.
      History history = iterator.next();
      //Discard the first segment in the list if the worm
      // has met its length requirement.  This will keep
      // the length of the worm constant.
      if(tailData.size() > wormLength && cnt == 0){ 
        iterator.remove();
      }//end if
      
      g.drawImage(history.image,
                  history.x,
                  history.y,
                  component);
      cnt++;
    }//end while
  }//end drawSpriteImage()
  //-----------------------------------------------------//

  public boolean testCollision(Sprite testSprite){
    // Check for collision with another sprite
    if(testSprite != this){
      return spaceOccupied.intersects(
                            testSprite.getSpaceOccupied());
    }//end if
    return false;
  }//end testCollision
}//end Sprite class
//=======================================================//

//An object of this class is used to contain state 
// information for each segment of each worm.
class History{
  Image image;
  int x;
  int y;
  
  public History(Image image,int x,int y){
    this.image = image;
    this.x = x;
    this.y = y;
  }//end constructor
}//end class History
//=======================================================//

//The animation is played out by drawing images on an
// object of this class.  The object is placed in the 
// center of an undecorated non-resizable JFrame object
// that is displayed in Full-Screen Exclusive Mode.
//Most of the code in this class was applied to the JFrame
// object in the earlier program named Animate03, because
// in that case, the images were drawn directly on the
// JFrame object.
class AnimationPanel extends JPanel implements Runnable{
  private Image offScreenImage;
  private Image backGroundImage;
  private Image[] gifImages = new Image[6];
  private Graphics offScreenGraphicsCtx;
  private Thread animationThread;
  private MediaTracker mediaTracker;
  private SpriteManager spriteManager;
  //Animation display rate, 12fps
  private int animationDelay = 83;
  private Random rand = 
                    new Random(System.currentTimeMillis());
  private javax.swing.Timer animationTimer;
  //-----------------------------------------------------//
  
  public AnimationPanel(){//constructor
    // Load and track the images
    mediaTracker = new MediaTracker(this);
    
    //Get and track the background image.  Note that this
    // background image is appropriate only for a screen
    // size of 1024x768.  For a different screen size, you
    // will need to use a different background image file.
    backGroundImage = Toolkit.getDefaultToolkit().
                              getImage("background03.gif");
    
    mediaTracker.addImage(backGroundImage,0);
    
    //Note that it should be possible to use the following
    // code to load a smaller version of the image and
    // have it scaled to the required size as it is loaded,
    // but this doesn't seem to work properly.  (I probably
    // just don't understand how it is supposed to work.)
//    backGroundImage = Toolkit.getDefaultToolkit().
//                            getImage("background02.gif");
//    mediaTracker.addImage(backGroundImage,0,1024,768);
    
    //Get and track 6 images to use for sprites
    gifImages[0] = Toolkit.getDefaultToolkit().
                                   getImage("redball.gif");
    mediaTracker.addImage(gifImages[0],0);
    gifImages[1] = Toolkit.getDefaultToolkit().
                                 getImage("greenball.gif");
    mediaTracker.addImage(gifImages[1],0);
    gifImages[2] = Toolkit.getDefaultToolkit().
                                  getImage("blueball.gif");
    mediaTracker.addImage(gifImages[2],0);
    gifImages[3] = Toolkit.getDefaultToolkit().
                                getImage("yellowball.gif");
    mediaTracker.addImage(gifImages[3],0);
    gifImages[4] = Toolkit.getDefaultToolkit().
                                getImage("purpleball.gif");
    mediaTracker.addImage(gifImages[4],0);
    gifImages[5] = Toolkit.getDefaultToolkit().
                                getImage("orangeball.gif");
    mediaTracker.addImage(gifImages[5],0);
    
    //Block and wait for all images to be loaded
    try{
      mediaTracker.waitForID(0);
    }catch(InterruptedException e){
      System.out.println(e);
    }//end catch
    
    //Instantiate an animation thread and start it running.
    animationThread = new Thread(this);
    animationThread.start();
    
    //Instantiate a Timer object and register an anonymous
    // ActionListener on it using the peculiar listener
    // registration process for a Timer object.  The 
    // Timer will be started in the run method of the
    // animationThread.
    animationTimer = new javax.swing.Timer(animationDelay,
      new ActionListener(){
        public void actionPerformed(ActionEvent e){
          //Update the sprites
          spriteManager.updateSprites();
          //Update the animation panel on the screen
          activeRenderer(getGraphics());
        }//end actionPerformed
      }//end new ActionListener
    );//end new javax.swing.Timer

  }//end constructor
  //-----------------------------------------------------//

  //This method is used to draw directly on the screen
  // using Active Rendering, without invoking the repaint
  // method.
  private void activeRenderer(Graphics g){
    //Create the offscreen graphics context
    if(offScreenGraphicsCtx == null){
      offScreenImage = 
             createImage(getSize().width,getSize().height);
      offScreenGraphicsCtx = offScreenImage.getGraphics();
    }//end if

    // Draw the sprites offscreen
    spriteManager.drawScene(offScreenGraphicsCtx);

    // Draw the scene onto the screen
    if(offScreenImage != null){
      g.drawImage(offScreenImage,0,0,this);
    }//end if

  }//end activeRenderer method
  //-----------------------------------------------------//
  
  public void run(){
    //Create and add sprites to the sprite manager
    
    //Delay until the width and the height of the
    // AnimationPanel stabilize in Full-Screen mode.  There
    // is probably a better way to do this, but I don't
    // know what it is.  In any event, this happens only
    // once while the program is getting started and
    // switching to Full-Screen Exclusive Mode.
    while(getWidth() == 0){
      System.out.print(".");
    }//end while loop
    while(getHeight() == 0){
      System.out.print(".");
    }//end while loop

    spriteManager = new SpriteManager(
                 new BackgroundImage(this,backGroundImage),
                 getWidth(),
                 getHeight());
    //Create 200 sprites from 6 gif files.
    for(int cnt = 0;cnt < 200;cnt++){
      Point position = 
                 spriteManager.getEmptyPosition(
                 new Dimension(gifImages[0].getWidth(this),
                 gifImages[0].getHeight(this)));
      spriteManager.addSprite(
                             makeSprite(position,cnt % 6));
    }//end for loop

    animationTimer.start();//Start the animation timer

  }//end run method 
  //-----------------------------------------------------//
  
  private Sprite makeSprite(Point position,int imageIndex){
    return new Sprite(this,
                      gifImages,
                      position,
                      new Point(rand.nextInt() % 5,
                              rand.nextInt() % 5));
  }//end makeSprite()
  //-----------------------------------------------------//
}//end AnimationPanel

Listing 27