KeyListener in an Applet
i am trying to find the functions that allow me to use key events to move and object around the screen.
im geussing you would need the
KeyEvent.KEY_PRESSED
KeyEvent.KEY_RELEASED
KeyEvent.KEY_TYPED
commands but im unsure of how to use them to make the object move.
if any one could point me in the right direction or tell me of a site/tutorial to help me it would be much appreciated.
Thanks
Here is a smallo program that will get you up and going
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class ball extends JFrame implements KeyListener{
JButton button = new JButton("Move");
int a = 5;
int b = 5;
public ball() {
super("My moveing button");
setSize(400,400);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container pane = getContentPane();
FlowLayout flow = new FlowLayout();
pane.setLayout(null);
button.addKeyListener(this);
button.setBounds(a,b,100,100);
pane.add(button);
setVisible(true);
public void keyTyped(KeyEvent input) {
public void keyPressed(KeyEvent txt) {
if(txt.getKeyCode()== txt.VK_UP) {b--;
button.setBounds(a,b,100,100); }
if(txt.getKeyCode()== txt.VK_DOWN) {b++;
button.setBounds(a,b,100,100);}
if(txt.getKeyCode()== txt.VK_LEFT) {a--;
button.setBounds(a,b,100,100); }
if(txt.getKeyCode()== txt.VK_RIGHT) { a++;
button.setBounds(a,b,100,100); }
//use the arrow keys to move the button around
public void keyReleased(KeyEvent txt) {}
public static void main(String[] args) {
ball ba = new ball();
[/b]GOOD LUCK[/b]
Similar Messages
-
Adding a KeyListener to java applet
I'm going to post this again, because I didn't really understand the last answer.. I know how to add KeyListeners to textfields and buttons, etc, but how do I add it to the applet itself.. I want to do this because I have a painted box on the screen and I want it to move its position everytime I hit the up key.. But I can't add the keylistener to anything but textfields and stuff. I dont know how to do it. Can u please help.. Someone told me JApplet.addKeyListener(this); but I tried it and it didn't work.. It gave me an error cannot find symbol JApplet, I dont have a variable for my whole applet, and I'm not sure how to create one either. Can anyone help?
I'm going to post this again, because I didn't really
understand the last answer.. That's no excuse for cross posting.
http://forum.java.sun.com/thread.jspa?threadID=5215206 -
Keylistener broken when applet implemented into application
I am currently trying to imbed my "Game" into an application to make a game menu for it. However, when
i try and do this the game loads fine but my keylistener doesnt work.
I am using the code.
import java.awt.*;
import java.applet.*;
public class RunApplets_BROKEN
public static void main (String [] args)
Applet myApplet = new Bomberman_Version_Aplha_EDITABLE (); // define applet of interest
Frame myFrame = new Frame ("Applet Holder"); // create frame with title
// Call applet's init method
myApplet.init ();
// add applet to the frame
myFrame.add (myApplet, BorderLayout.CENTER);
myFrame.setSize (500, 600);
myFrame.setVisible (true); // usual step to make frame visible
} // end main
} // end class
I am wondering if the problems exists in where i am calling the keylister into the application but it does not call
the methods (such as keylistener), altho i call the init method in the application. Do i have to call the keypressed and such methods also?The way you are approaching this is not a good idea though.
Don't try and plug an applet into a Frame. It's not that simple. An applet has a context for example and yours doesn't. If you have a program that you want to use as both an applet and an application then you should make your applet just behave as the bootstrapping component and take your GUI stuff to another class. Then you can use this common class (maybe a JPanel/Panel) in multiple places (Frame, Applet, etc). -
[SOLVED] Trouble adding KeyListener to applet container
I'm trying to add a KeyListener to my applet container but I'm not seeing anything happen when I press keys. My source is
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class KeyTest extends JApplet implements KeyListener, ActionListener {
/** Handle the key typed event from the text field. */
public void keyTyped(KeyEvent e) {
int id = e.getID();
System.out.println(id);
/** Handle the key pressed event from the text field. */
public void keyPressed(KeyEvent e) {
int id = e.getID();
System.out.println(id);
/** Handle the key released event from the text field. */
public void keyReleased(KeyEvent e) {
int id = e.getID();
System.out.println(id);
/** Handle the button click. */
public void actionPerformed(ActionEvent e) {
System.out.println("action");
public void init(){
getContentPane().addKeyListener(this);
}edit: nm I just had to change getContentPane() to this. I swear I tried that earlier and it didn't work though.
Edited by: ner0 on Jun 30, 2008 10:52 AMOops, forgot you were using awt instead of swing.
The ScrollPane class has a getHAdjustable() method that returns an Adjustable, which is actually a ScrollPaneAdjustable. I started looking at that class, but didn't see how to adjust the policy, although the ScrollPane api says that's the class that determines the policy.
http://java.sun.com/j2se/1.5.0/docs/api/java/awt/ScrollPaneAdjustable.html
http://java.sun.com/j2se/1.5.0/docs/api/java/awt/ScrollPane.html#getHAdjustable() -
KeyListener kinda deaf (in simple game)
Hey everyone...
I'm trying to write a simple word-guessing game (Lingo, user should guess 5 letter words etc).
I've created some custom AWT Components (sorry for the dutch naming):
Lettervak: extends Canvas
Woordveld: extends Container and contains Lettervak's
Speelveld: extends Container and contains Woordveld's
The Speelveld (playing field in english) is the main component I want to talk to from the applet itself.
I don't care where a key is typed, I just want to be able to send the message to the correct component so the letter can be drawn in a Lettervak. So I though I'd add a KeyListener to the Applet itself.
It registers (I can see in the debugger), but it doesn't receive any key events (I can tell by adding a breakpoint there, so it's not in code further down).
Can anyone tell me what I'm doing wrong? Below is the code of the Applet itself:
(may look a bit messy, because I've been fooling around to get it to work, sorry...)
package lingo;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class LingoWeb
extends Applet {
private boolean isStandalone = false;
// Components
Speelveld grid;
//Get a parameter value
public String getParameter(String key, String def) {
return isStandalone ? System.getProperty(key, def) :
(getParameter(key) != null ? getParameter(key) : def);
//Construct the applet
public LingoWeb() {
this.addKeyListener( new SpeelveldListener() );
//Initialize the applet
public void init() {
try {
jbInit();
catch (Exception e) {
e.printStackTrace();
//Component initialization
private void jbInit() throws Exception {
Speelveld grid = new Speelveld( 10, 20, 5, 5, 40 );
this.setFocusable( true );
this.requestFocusInWindow();
this.setLayout(null);
this.add(grid);
this.repaint();
//Get Applet information
public String getAppletInfo() {
return "Applet Information";
//Get parameter info
public String[][] getParameterInfo() {
return null;
class SpeelveldListener implements KeyListener {
public void keyTyped( KeyEvent e ) {
char c = e.getKeyChar();
grid.invoer(c);
public void keyPressed( KeyEvent e ) {
System.out.println( e.getKeyChar() );
public void keyReleased( KeyEvent e ) {}
Thanks!
Tim./* <applet code="AppletKeyTest" width="400"
height="300"></applet>
* use: >appletviewer AppletKeyTest.java
import java.applet.Applet;
import java.awt.*;
import java.awt.font.*;
import java.awt.event.*;
public class AppletKeyTest extends Applet
public void init()
setLayout(new BorderLayout());
add(new Speelveld());
public static void main(String[] args)
Applet applet = new AppletKeyTest();
Frame f = new Frame(applet.getClass().getName());
f.addWindowListener(new WindowAdapter()
public void windowClosing(WindowEvent e)
System.exit(0);
f.add(applet);
f.setSize(400,300);
f.setLocation(200,200);
applet.init();
applet.start();
f.setVisible(true);
class Speelveld extends Canvas
Font font;
String text;
public Speelveld()
font = new Font("lucida bright regular", Font.PLAIN,
48);
text = "a";
addKeyListener(new SpeelveldListener(this));
setFocusable(true);
requestFocusInWindow();
public void paint(Graphics g)
super.paint(g);
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
int w = getWidth();
int h = getHeight();
g2.setFont(font);
FontRenderContext frc = g2.getFontRenderContext();
float textWidth = (float)font.getStringBounds(text,
frc).getWidth();
LineMetrics lm = font.getLineMetrics(text, frc);
float x = (w - textWidth)/2;
float y = (h + lm.getHeight())/2 - lm.getDescent();
g2.drawString(text, x, y);
public void update(Graphics g)
paint(g);
public void setText(String text)
this.text = text;
repaint();
class SpeelveldListener extends KeyAdapter
Speelveld speelveld;
public SpeelveldListener(Speelveld s)
speelveld = s;
public void keyPressed(KeyEvent e)
String s = KeyEvent.getKeyText(e.getKeyCode());
speelveld.setText(s);
}Yikes!
don't do much processing in the listener methods.
Certainly DONT call drawn out methods. I wouldn't call ANY methods.
Here is a quote...
"The most important rule to keep in mind about event listeners that they should execute very quickly. Because all drawing and event-listening methods are executed in the same thread, a slow event-listener method can make the program seem unresponsive and slow to repaint itself. If you need to perform some lengthy operation as the result of an event, do it by starting up another thread (or somehow sending a request to another thread) to perform the operation. For help on using threads, see How to Use Threads."
From here.
http://java.sun.com/docs/books/tutorial/uiswing/events/generalrules.html
There are those who will tell you that calling methods and adding other
general inefficiencies to you code doesn't matter, but it in fact does and this
is one area where it is readilly apparent.
In my HyperView API my listener routines simply bit codes the event,
pops it on a list, and then calls notify() to another thread which then does the processing.
This allows more cycles for the AWT-Event thread to grab events because it doesn't
have to then process them. It also smooths out the differences between different
operating system event models.
Good Luck!
(T) -
Issues with ActionListener and KeyListener, what am i doing wrong?
basically the program will complie, but not run properly, in appletviewer or a browser. The code for the buttons will be added later, but the test code seems to be working ok. The code for KeyListener does not move the square in the applet as it should, and when i close the applet it will dump a long error message to the dos window. if i comment out Action listener then KeyListener will work fine. if i comment out KeyListener then the applet will close with no error message to the dos window.
i'm new to java and i don't know if i am doing anything wrong. please help, thankyou.
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class Project22 extends Applet implements KeyListener, ActionListener {
private int score = 0;
private int speed = 5;
private int [] frame = {500, 500};
private int [] sqr_loc = {235, 235};
private char keyinput;
private Button new_b = new Button("New Ball");
private Button ext_app = new Button("Exit");
private int junk = 0; // debug
private Label message = new Label("start"); // debug
public void actionPerformed(ActionEvent event) {
Object source = event.getSource();
if(source == new_b) { // not coded yet
++junk;
message.setText(Integer.toString(junk));
else if(source == ext_app) { // not coded yet
++junk;
message.setText(Integer.toString(junk));
public void keyTyped(KeyEvent event) {}
public void keyPressed(KeyEvent event) {
int keycode = event.getKeyCode();
if(keycode == KeyEvent.VK_RIGHT) {
if(sqr_loc[0] < 475) {
sqr_loc[0] += speed;
repaint();
else if(keycode == KeyEvent.VK_LEFT) {
if(sqr_loc[0] > 0) {
sqr_loc[0] -= speed;
repaint();
else if(keycode == KeyEvent.VK_UP) {
if(sqr_loc[1] > 0) {
sqr_loc[1] -= speed;
repaint();
else if(keycode == KeyEvent.VK_DOWN) {
if(sqr_loc[1] < 475) {
sqr_loc[1] += speed;
repaint();
public void keyReleased(KeyEvent event) {}
public void paint(Graphics g) {
g.drawRect(sqr_loc[0], sqr_loc[1], 25, 25);
} // end paint
public void init() {
add(new_b);
add(ext_app);
add(message);
new_b.addActionListener(this);
ext_app.addActionListener(this);
addKeyListener(this);
requestFocus();
} // end Project22Perhaps the error message can help to determine the problem?
-
i made the progeam below to try to move a box around the screen by typing on the key bourd. but it doesnt work. what am i doing wrong.
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.awt.event.KeyEvent.*;
public class GTest extends Applet implements KeyListener{
private int X,Y;
public void paint(Graphics g){
g.setColor(Color.black);
g.drawRect(0,0,200,200);
g.setColor(Color.white);
g.fillRect(1,1,199,199);
g.setColor(Color.black);
g.fillRect(X,Y,X+10,Y+10);
public void keyTyped(KeyEvent e){
public void keyPressed(KeyEvent e){
char c=e.getKeyChar();
if(c=='5'){Y++;}
else if(c=='2'){Y--;}
else if(c=='3'){X++;}
else if(c=='1'){X--;}
repaint();
public void keyReleased(KeyEvent e){}
}Hey BigNester,
In the init() method of your applet, you have to add your class as a keyListener to your applet.
add the following methods:
// register this class as a key listener
public void init() {
addKeyListener(this);
// unregister this class as a key listener
public void destory() {
removeKeyListener(this);
Later,
Bud -
Keylistener breaks when implementing applet into application
I am currently trying to imbed my "Game" into an application to make a game menu for it. However, when
i try and do this the game loads fine but my keylistener doesnt work.
I am using the code.
import java.awt.*;
import java.applet.*;
public class RunApplets_BROKEN
public static void main (String [] args)
Applet myApplet = new Bomberman_Version_Aplha_EDITABLE (); // define applet of interest
Frame myFrame = new Frame ("Applet Holder"); // create frame with title
// Call applet's init method
myApplet.init ();
// add applet to the frame
myFrame.add (myApplet, BorderLayout.CENTER);
myFrame.setSize (500, 600);
myFrame.setVisible (true); // usual step to make frame visible
} // end main
} // end class
I know this is bad programming and i am trying to keep it simple, however when i do this to my other program it works fine. So i dont understand. Could anyone please help?Intentional multi-post
[http://forums.sun.com/thread.jspa?threadID=5360722]
You were given two answers yesterday. Don't start a new thread because you didn't like them, that just wastes peoples time. -
Adding keylistener to the entire applet
How can I addKeyListener(this) to the entire applet frame? I know in applications you name the frame and everything then can just add it to whatever you named it, but applets make the frame on their own. So what do I tell to addkeylistener to?
lol thanks
I just put
addKeyListener(this);whatever.. thanks :) -
Using getter/setter for returing a string variable to display on an Applet
have two classes called, class A and class testA.
class A contains an instance variable called title and one getter & setter method. class A as follow.
public class A extends Applet implements Runnable, KeyListener
//Use setter and getter of the instance variable
private String title;
public void init()
ASpriteFactory spriteFactory = ASpriteFactory.getSingleton();
// Find the size of the screen .
Dimension theDimension = getSize();
width = theDimension.width;
height = theDimension.height;
//Create new ship
ship = spriteFactory.createNewShip();
fwdThruster = spriteFactory.createForwardThruster();
revThruster = spriteFactory.createReverseThruster();
ufo = spriteFactory.createUfo();
missile = spriteFactory.createMissile();
generateStars();
generatePhotons();
generateAsteroids();
generateExplosions();
initializeFonts();
initializeGameData();
//Example from Instructor
//setMyControlPanel( new MyControlPanel(this) );
// new for JDK 1.2.2
addKeyListener(this);
requestFocus();
public void update(Graphics theGraphics)
// Create the offscreen graphics context, if no good one exists.
if (offGraphics == null || width != offDimension.width || height != offDimension.height)
// This better be the same as when the game was started
offDimension = getSize();
offImage = createImage(offDimension.width, offDimension.height);
offGraphics = offImage.getGraphics();
offGraphics.setFont(font);
displayStars();
displayPhotons();
displayMissile();
displayAsteroids();
displayUfo();
//displayShip();
//Load the game with different color of the space ship
displayNewShip();
displayExplosions();
displayStatus();
displayInfoScreen();
// Copy the off screen buffer to the screen.
theGraphics.drawImage(offImage, 0, 0, this);
private void displayInfoScreen()
String message;
if (!playing)
offGraphics.setColor(Color.white);
offGraphics.drawString("\'A\' to Change Font Attribute", 25, 35);
offGraphics.drawString(getTitle(), (width - fontMetrics.stringWidth(message)) / 2, height / 2
- fontHeight);
message = "The Training Mission";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 2);
message = "Name of Author";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 2
+ fontHeight);
message = "Original Copyright 1998-1999 by Mike Hall";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 2
+ (fontHeight * 2));
if (!loaded)
message = "Loading sounds...";
int barWidth = 4 * fontWidth + fontMetrics.stringWidth(message);
int barHeight = fontHeight;
int startX = (width - barWidth) / 2;
int startY = 3 * height / 4 - fontMetrics.getMaxAscent();
offGraphics.setColor(Color.black);
offGraphics.fillRect(startX, startY, barWidth, barHeight);
offGraphics.setColor(Color.gray);
if (clipTotal > 0)
offGraphics.fillRect(startX, startY, (barWidth * clipsLoaded / clipTotal), barHeight);
offGraphics.setColor(Color.white);
offGraphics.drawRect(startX, startY, barWidth, barHeight);
offGraphics
.drawString(message, startX + 2 * fontWidth, startY + fontMetrics.getMaxAscent());
else
message = "Game Over";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 4);
message = "'S' to Start";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 4
+ fontHeight);
else if (paused)
offGraphics.setColor(Color.white);
message = "Game Paused";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 4);
public String getTitle() {
System.out.print(title);
return title;
public void setTitle(String title) {
this.title = title;
}displayInfoScreen method in class A calls out for getTitle( ) to be displayed on an applet as an initial display string for the application.
The instance variable title is set by setTitle method which is called out in class testA as follow,
public class testA extends TestCase
* testASprite constructor comment.
* @param name
* java.lang.String
public testA(String name)
super(name);
* Insert the method's description here.
* @param args
* java.lang.String[]
public static void main(String[] args)
junit.textui.TestRunner.run(suite());
// need to figure out how to get rid of the frame in this test
System.exit(0);
public static Test suite()
return new TestSuite(testA.class);
* Basic create and simple checks
public void testCreate()
A theGame = new A();
assertNotNull("game was null!", theGame);
* Basic create and simple checks
public void testInit()
A theGame = new A();
Frame gameFrame = new Frame("THE GAME");
gameFrame.add(theGame);
int width = 640;
int height = 480;
gameFrame.setSize(width, height);
// must pack to get graphics peer
gameFrame.pack();
theGame.resize(width, height);
theGame.setTitle("TEST THE GAME");
theGame.init();
assertEquals("ASprite width not set", A.width, width);
gameFrame.dispose();
gameFrame.remove(theGame);
}Basically, class testA invokes the init( ) method in class A and start the applet application. However, it displays a white blank display. If I change the getTitle( ) in the displayInfoScreen method to a fixed string, it works fine. Did I forget anything as far as using getter & setter method? Do I have to specify some type of handle to sync between setter and getter between two classes? Any feedback will be greatly appreciated.
Thanks.Your class A extends runnable which leads me to believe that this is a multi-threaded application. In that case, title may or may not be a shared variable. Who knows? It's impossible to tell from what you posted.
Anyway, what is happening is that your applet is being painted by the JFrame before setTitle is called. After that, who knows what's happening. It's a complicated application. I suspect that if you called setTitle before you added the applet to the frame, it would work. -
Problem converting a (working) Java program into an applet
When I'm trying to access an Image through a call to :
mediaTracker = new MediaTracker(this);
backGroundImage = getImage(getDocumentBase(), "background.gif");
mediaTracker.addImage(backGroundImage, 0);
I'm getting a nullPointerException as a result of the call to getDocumentBase() :
C:\Chantier\Java\BallsApplet
AppletViewer testBallsApplet.htmljava.lang.NullPointerException
at java.applet.Applet.getDocumentBase(Applet.java:125)
at Balls.<init>(Balls.java:84)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstruct
orAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingC
onstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:274)
at java.lang.Class.newInstance0(Class.java:296)
at java.lang.Class.newInstance(Class.java:249)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:548)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:477)
at sun.applet.AppletPanel.run(AppletPanel.java:290)
at java.lang.Thread.run(Thread.java:536)
It seems very weird to me... :-/
(all the .gif files are in the same directory than the .class files)
The problem appears with AppletViewer trying to open an HTML file
containing :
<HTML>
<APPLET CODE="Balls.class" WIDTH=300 HEIGHT=211>
</APPLET>
</HTML>
(I tried unsuccessfully the CODEBASE and ARCHIVE attributes, with and without putting the .gif and .class into a .jar file)
I can't find the solution by myself, so, I'd be very glad if someone could help
me with this... Thank you very much in advance ! :-)
You'll find below the source of a small game that I wrote and debugged (without
problem) and that I'm now (unsuccessfully) trying to convert into an Applet :
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.net.URL;
public class Balls extends java.applet.Applet implements Runnable, KeyListener
private Image offScreenImage;
private Image backGroundImage;
private Image[] gifImages = new Image[6];
private Image PressStart ;
private Sprite pressStartSprite = null ;
private Image YouLose ;
private Sprite YouLoseSprite = null ;
private Image NextStage ;
private Sprite NextStageSprite = null ;
private Image GamePaused ;
private Sprite GamePausedSprite = null ;
//offscreen graphics context
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 int message = 0 ; // 0 = no message (normal playing phase)
// 1 = press space to start
// 2 = press space for next level
// 3 = game PAUSED, press space to unpause
// 4 = You LOSE
public static void main(String[] args)
try
new Balls() ;
catch (java.net.MalformedURLException e)
System.out.println(e);
}//end main
public void start()
//Create and start animation thread
animationThread = new Thread(this);
animationThread.start();
public void init()
try
new Balls() ;
catch (java.net.MalformedURLException e)
System.out.println(e);
public Balls() throws java.net.MalformedURLException
{//constructor
// Load and track the images
mediaTracker = new MediaTracker(this);
backGroundImage = getImage(getDocumentBase(), "background.gif");
mediaTracker.addImage(backGroundImage, 0);
PressStart = getImage(getDocumentBase(), "press_start.gif");
mediaTracker.addImage(PressStart, 0);
NextStage = getImage(getDocumentBase(), "stage_complete.gif");
mediaTracker.addImage(NextStage, 0);
GamePaused = getImage(getDocumentBase(), "game_paused.gif");
mediaTracker.addImage(GamePaused, 0);
YouLose = getImage(getDocumentBase(), "you_lose.gif");
mediaTracker.addImage(YouLose, 0);
//Get and track 6 images to use
// for sprites
gifImages[0] = getImage(getDocumentBase(), "blueball.gif");
mediaTracker.addImage(gifImages[0], 0);
gifImages[1] = getImage(getDocumentBase(), "redball.gif");
mediaTracker.addImage(gifImages[1], 0);
gifImages[2] = getImage(getDocumentBase(), "greenball.gif");
mediaTracker.addImage(gifImages[2], 0);
gifImages[3] = getImage(getDocumentBase(), "yellowball.gif");
mediaTracker.addImage(gifImages[3], 0);
gifImages[4] = getImage(getDocumentBase(), "purpleball.gif");
mediaTracker.addImage(gifImages[4], 0);
gifImages[5] = getImage(getDocumentBase(), "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
//Base the Frame size on the size
// of the background image.
//These getter methods return -1 if
// the size is not yet known.
//Insets will be used later to
// limit the graphics area to the
// client area of the Frame.
int width = backGroundImage.getWidth(this);
int height = backGroundImage.getHeight(this);
//While not likely, it may be
// possible that the size isn't
// known yet. Do the following
// just in case.
//Wait until size is known
while(width == -1 || height == -1)
System.out.println("Waiting for image");
width = backGroundImage.getWidth(this);
height = backGroundImage.getHeight(this);
}//end while loop
//Display the frame
setSize(width,height);
setVisible(true);
//setTitle("Balls");
//Anonymous inner class window
// listener to terminate the
// program.
this.addWindowListener
(new WindowAdapter()
{public void windowClosing(WindowEvent e){System.exit(0);}});
// Add a key listener for keyboard management
this.addKeyListener(this);
}//end constructor
public void run()
Point center_place = new Point(
backGroundImage.getWidth(this)/2-PressStart.getWidth(this)/2,
backGroundImage.getHeight(this)/2-PressStart.getHeight(this)/2) ;
pressStartSprite = new Sprite(this, PressStart, center_place, new Point(0, 0),true);
center_place = new Point(
backGroundImage.getWidth(this)/2-NextStage.getWidth(this)/2,
backGroundImage.getHeight(this)/2-NextStage.getHeight(this)/2) ;
NextStageSprite = new Sprite(this, NextStage, center_place, new Point(0, 0),true);
center_place = new Point(
backGroundImage.getWidth(this)/2-GamePaused.getWidth(this)/2,
backGroundImage.getHeight(this)/2-GamePaused.getHeight(this)/2) ;
GamePausedSprite = new Sprite(this, GamePaused, center_place, new Point(0, 0),true);
center_place = new Point(
backGroundImage.getWidth(this)/2-YouLose.getWidth(this)/2,
backGroundImage.getHeight(this)/2-YouLose.getHeight(this)/2) ;
YouLoseSprite = new Sprite(this, YouLose, center_place, new Point(0, 0),true);
BackgroundImage bgimage = new BackgroundImage(this, backGroundImage) ;
for (;;) // infinite loop
long time = System.currentTimeMillis();
message = 1 ; // "press start to begin"
while (message != 0)
repaint() ;
try
time += animationDelay;
Thread.sleep(Math.max(0,time - System.currentTimeMillis()));
catch (InterruptedException e)
System.out.println(e);
}//end catch
boolean you_lose = false ;
for (int max_speed = 7 ; !you_lose && max_speed < 15 ; max_speed++)
for (int difficulty = 2 ; !you_lose && difficulty < 14 ; difficulty++)
boolean unfinished_stage = true ;
spriteManager = new SpriteManager(bgimage);
spriteManager.setParameters(difficulty, max_speed) ;
//Create 15 sprites from 6 gif
// files.
for (int cnt = 0; cnt < 15; cnt++)
if (cnt == 0)
Point position = new Point(
backGroundImage.getWidth(this)/2-gifImages[0].getWidth(this)/2,
backGroundImage.getHeight(this)/2-gifImages[0].getHeight(this)/2) ;
spriteManager.addSprite(makeSprite(position, 0, false));
else
Point position = spriteManager.
getEmptyPosition(new Dimension(gifImages[0].getWidth(this),
gifImages[0].getHeight(this)));
if (cnt < difficulty)
spriteManager.addSprite(makeSprite(position, 1, true));
else
spriteManager.addSprite(makeSprite(position, 2, true));
}//end for loop
time = System.currentTimeMillis();
while (!spriteManager.getFinishedStage() && !spriteManager.getGameOver())
// Loop, sleep, and update sprite
// positions once each 83
// milliseconds
spriteManager.update();
repaint();
try
time += animationDelay;
Thread.sleep(Math.max(0,time - System.currentTimeMillis()));
catch (InterruptedException e)
System.out.println(e);
}//end catch
}//end while loop
if (spriteManager.getGameOver())
message = 4 ;
while (message != 0)
spriteManager.update();
repaint();
try
time += animationDelay;
Thread.sleep(Math.max(0,time - System.currentTimeMillis()));
catch (InterruptedException e)
System.out.println(e);
}//end catch
you_lose = true ;
if (spriteManager.getFinishedStage())
message = 2 ;
while (message != 0)
spriteManager.update();
repaint();
try
time += animationDelay;
Thread.sleep(Math.max(0,time - System.currentTimeMillis()));
catch (InterruptedException e)
System.out.println(e);
}//end catch
} // end for difficulty loop
} // end for max_speed
} // end infinite loop
}//end run method
private Sprite makeSprite(Point position, int imageIndex, boolean wind)
return new Sprite(
this,
gifImages[imageIndex],
position,
new Point(rand.nextInt() % 5,
rand.nextInt() % 5),
wind);
}//end makeSprite()
//Overridden graphics update method
// on the Frame
public void update(Graphics g)
//Create the offscreen graphics
// context
if (offScreenGraphicsCtx == null)
offScreenImage = createImage(getSize().width,
getSize().height);
offScreenGraphicsCtx = offScreenImage.getGraphics();
}//end if
if (message == 0)
// Draw the sprites offscreen
spriteManager.drawScene(offScreenGraphicsCtx);
else if (message == 1)
pressStartSprite.drawSpriteImage(offScreenGraphicsCtx);
else if (message == 2)
NextStageSprite.drawSpriteImage(offScreenGraphicsCtx);
else if (message == 3)
GamePausedSprite.drawSpriteImage(offScreenGraphicsCtx);
else if (message == 4)
YouLoseSprite.drawSpriteImage(offScreenGraphicsCtx);
// Draw the scene onto the screen
if(offScreenImage != null)
g.drawImage(offScreenImage, 0, 0, this);
}//end if
}//end overridden update method
//Overridden paint method on the
// Frame
public void paint(Graphics g)
//Nothing required here. All
// drawing is done in the update
// method above.
}//end overridden paint method
// Methods to handle Keyboard event
public void keyPressed(KeyEvent evt)
int key = evt.getKeyCode(); // Keyboard code for the pressed key.
if (key == KeyEvent.VK_SPACE)
if (message != 0)
message = 0 ;
else
message = 3 ;
if (key == KeyEvent.VK_LEFT)
if (spriteManager != null)
spriteManager.goLeft() ;
else if (key == KeyEvent.VK_RIGHT)
if (spriteManager != null)
spriteManager.goRight() ;
else if (key == KeyEvent.VK_UP)
if (spriteManager != null)
spriteManager.goUp() ;
else if (key == KeyEvent.VK_DOWN)
if (spriteManager != null)
spriteManager.goDown() ;
if (spriteManager != null)
spriteManager.setMessage(message) ;
public void keyReleased(KeyEvent evt)
public void keyTyped(KeyEvent e)
char key = e.getKeyChar() ;
//~ if (key == 's')
//~ stop = true ;
//~ else if (key == 'c')
//~ stop = false ;
//~ spriteManager.setStop(stop) ;
}//end class Balls
//===================================//
class BackgroundImage
private Image image;
private Component component;
private Dimension size;
public BackgroundImage(
Component component,
Image image)
this.component = component;
size = component.getSize();
this.image = image;
}//end construtor
public Dimension getSize(){
return size;
}//end getSize()
public Image getImage(){
return image;
}//end getImage()
public void setImage(Image image){
this.image = image;
}//end setImage()
public void drawBackgroundImage(Graphics g)
g.drawImage(image, 0, 0, component);
}//end drawBackgroundImage()
}//end class BackgroundImage
//===========================
class SpriteManager extends Vector
private BackgroundImage backgroundImage;
private boolean finished_stage = false ;
private boolean game_over = false ;
private int difficulty ;
private int max_speed ;
public boolean getFinishedStage()
finished_stage = true ;
for (int cnt = difficulty ; cnt < size(); cnt++)
Sprite sprite = (Sprite)elementAt(cnt);
if (!sprite.getEaten())
finished_stage = false ;
return finished_stage ;
public boolean getGameOver() {return game_over ;}
public void setParameters(int diff, int speed)
difficulty = diff ;
max_speed = speed ;
finished_stage = false ;
game_over = false ;
Sprite sprite;
for (int cnt = 0;cnt < size(); cnt++)
sprite = (Sprite)elementAt(cnt);
sprite.setSpeed(max_speed) ;
public SpriteManager(BackgroundImage backgroundImage)
this.backgroundImage = backgroundImage ;
}//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
while (!empty && numTries++ < 100)
// Get a trial position
trialSpaceOccupied.x =
Math.abs(rand.nextInt() %
backgroundImage.
getSize().width);
trialSpaceOccupied.y =
Math.abs(rand.nextInt() %
backgroundImage.
getSize().height);
// Iterate through existing
// sprites, checking if position
// is empty
boolean collision = false;
for(int cnt = 0;cnt < size(); cnt++)
Rectangle testSpaceOccupied = ((Sprite)elementAt(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()
public void update()
Sprite sprite;
// treat special case of sprite #0 (the player)
sprite = (Sprite)elementAt(0);
sprite.updatePosition() ;
int hitIndex = testForCollision(sprite);
if (hitIndex != -1)
if (hitIndex < difficulty)
{ // if player collides with an hunter (red ball), he loose
sprite.setEaten() ;
game_over = true ;
else
// if player collides with an hunted (green ball), he eats the green
((Sprite)elementAt(hitIndex)).setEaten() ;
//Iterate through sprite list
for (int cnt = 1;cnt < size(); cnt++)
sprite = (Sprite)elementAt(cnt);
//Update a sprite's position
sprite.updatePosition();
//Test for collision. Positive
// result indicates a collision
hitIndex = testForCollision(sprite);
if (hitIndex >= 0)
//a collision has occurred
bounceOffSprite(cnt,hitIndex);
}//end if
}//end for loop
}//end update
public void setMessage(int message)
Sprite sprite;
//Iterate through sprite list
for (int cnt = 0;cnt < size(); cnt++)
sprite = (Sprite)elementAt(cnt);
//Update a sprite's stop status
sprite.setMessage(message);
}//end for loop
}//end update
public void goLeft()
Sprite sprite = (Sprite)elementAt(0);
sprite.goLeft() ;
public void goRight()
Sprite sprite = (Sprite)elementAt(0);
sprite.goRight() ;
public void goUp()
Sprite sprite = (Sprite)elementAt(0);
sprite.goUp() ;
public void goDown()
Sprite sprite = (Sprite)elementAt(0);
sprite.goDown() ;
private int testForCollision(Sprite testSprite)
//Check for collision with other
// sprites
Sprite sprite;
for (int cnt = 0;cnt < size(); cnt++)
sprite = (Sprite)elementAt(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 oneHitIndex, int otherHitIndex)
//Swap motion vectors for
// bounce algorithm
Sprite oneSprite = (Sprite)elementAt(oneHitIndex);
Sprite otherSprite = (Sprite)elementAt(otherHitIndex);
Point swap = oneSprite.getMotionVector();
oneSprite.setMotionVector(otherSprite.getMotionVector());
otherSprite.setMotionVector(swap);
}//end bounceOffSprite()
public void drawScene(Graphics g)
//Draw the background and erase
// sprites from graphics area
//Disable the following statement
// for an interesting effect.
backgroundImage.drawBackgroundImage(g);
//Iterate through sprites, drawing
// each sprite
for (int cnt = 0;cnt < size(); cnt++)
((Sprite)elementAt(cnt)).drawSpriteImage(g);
}//end drawScene()
public void addSprite(Sprite sprite)
addElement(sprite);
}//end addSprite()
}//end class SpriteManager
//===================================//
class Sprite
private Component component;
private Image image;
private Rectangle spaceOccupied;
private Point motionVector;
private Rectangle bounds;
private Random rand;
private int message = 0 ; // number of message currently displayed (0 means "no message" = normal game)
private int max_speed = 7 ;
private boolean eaten = false ; // when a green sprite is eaten, it is no longer displayed on screen
private boolean wind = true ;
private boolean go_left = false ;
private boolean go_right = false ;
private boolean go_up = false ;
private boolean go_down = false ;
public Sprite(Component component,
Image image,
Point position,
Point motionVector,
boolean Wind
//Seed a random number generator
// for this sprite with the sprite
// position.
rand = new Random(position.x);
this.component = component;
this.image = image;
setSpaceOccupied(new Rectangle(
position.x,
position.y,
image.getWidth(component),
image.getHeight(component)));
this.motionVector = motionVector;
this.wind = Wind ;
//Compute edges of usable graphics
// area in the Frame.
int topBanner = ((Container)component).getInsets().top;
int bottomBorder = ((Container)component).getInsets().bottom;
int leftBorder = ((Container)component).getInsets().left;
int rightBorder = ((Container)component).getInsets().right;
bounds = new Rectangle( 0 + leftBorder, 0 + topBanner
, component.getSize().width - (leftBorder + rightBorder)
, component.getSize().height - (topBanner + bottomBorder));
}//end constructor
public void setMessage(int message_number)
message = message_number ;
public void setSpeed(int speed)
max_speed = speed ;
public void goLeft()
go_left = true ;
public void goRight()
go_right = true ;
public void goUp()
go_up = true ;
public void goDown()
go_down = true ;
public void setEaten()
eaten = true ;
setSpaceOccupied(new Rectangle(4000,4000,0,0)) ;
public boolean getEaten()
return eaten ;
public Rectangle getSpaceOccupied()
return spaceOccupied;
}//end getSpaceOccupied()
void setSpaceOccupied(Rectangle spaceOccupied)
this.spaceOccupied = spaceOccupied;
}//setSpaceOccupied()
public 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()
public void setBounds(Rectangle bounds)
this.bounds = bounds;
}//end setBounds()
public void updatePosition()
Point position = new Point(spaceOccupied.x, spaceOccupied.y);
if (message != 0)
return ;
//Insert random behavior. During
// each update, a sprite has about
// one chance in 10 of making a
// random change to its
// motionVector. When a change
// occurs, the motionVector
// coordinate values are forced to
// fall between -7 and 7. This
// puts a cap on the maximum speed
// for a sprite.
if (!wind)
if (go_left)
motionVector.x -= 2 ;
if (motionVector.x < -15)
motionVector.x = -14 ;
go_left = false ;
if (go_right)
motionVector.x += 2 ;
if (motionVector.x > 15)
motionVector.x = 14 ;
go_right = false ;
if (go_up)
motionVector.y -= 2 ;
if (motionVector.y < -15)
motionVector.y = -14 ;
go_up = false ;
if (go_down)
motionVector.y += 2 ;
if (motionVector.y > 15)
motionVector.y = 14 ;
go_down = false ;
else if(rand.nextInt() % 7 == 0)
Point randomOffset =
new Point(rand.nextInt() % 3,
rand.nextInt() % 3);
motionVector.x += randomOffset.x;
if(motionVector.x >= max_speed)
motionVector.x -= max_speed;
if(motionVector.x <= -max_speed)
motionVector.x += max_speed ;
motionVector.y += randomOffset.y;
if(motionVector.y >= max_speed)
motionVector.y -= max_speed;
if(motionVector.y <= -max_speed)
motionVector.y += max_speed;
}//end if
//Move the sprite on the screen
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 in x
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
if(bounceRequired)
//save new motionVector
setMotionVector(
tempMotionVector);
//update spaceOccupied
setSpaceOccupied(position);
}//end updatePosition()
public void drawSpriteImage(Graphics g)
if (!eaten)
g.drawImage(image,
spaceOccupied.x,
spaceOccupied.y,
component);
}//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
//===================================//
Thanks for your help...Sorry,
Can you tell me how do you solve it because I have got the same problem.
Can you indicate me the topic where did you find solution.
Thank in advance. -
ActionPerformed method not working when applet is loaded in browser window.
Hey there guys. I need urgent help from anybody who has experience in deploying websites whose code is in java.
I am having two problems as mentioned below...
first, I have made a simple login screen using java swing and JApplet. there is a single button to login. the action performed for this button accesses a private method to check the username and password which are there in atext file. the applet is working perfectly in appletviewer but when i load the applet in a Internet Explorer window using HTML's Applet tag, the button is giving no response at all even when i enter the correct username and password.
I guess it is either not calling the private function that is checking the username and password from the tes=xt file or it can not access the file. Please help as soon as possible as this is related to my college project.
I am attaching the code herewith. Suggestions to improve the coding are also welcome.
the second problem is that while writing my second program for generating a form which registers a user the html is not at all loading the applet into the browser and also if im trying to access a file to write all the details into the console is showing numerous amount of error after i press the button which i can't not understand. the only thing i can understand is that it is related to file access permissions. If anybody could put some light on the working of worker threads and thread safe activities of SwingUtilities.invokeandWait method it would be really appreciable.
import java.io.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;
import javax.swing.plaf.*;
<applet code = "UserLogin" width = 300 height = 150>
</applet>
public class UserLogin extends JApplet implements ActionListener, KeyListener {
private JLabel lTitle;
private JLabel lUsername, lPassword;
private JTextField tUsername;
private JPasswordField tPassword;
private JButton bLogin;
private JLabel lLinkRegister, lLinkForgot;
private JLabel lEmpty = new JLabel(" ", JLabel.CENTER);
private JPanel panel1, panel2;
public void init() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
SwingUtilities.invokeAndWait(new Runnable() {
public void run() {
LoginGUI();
catch(Exception e) {
e.printStackTrace();
public void start() {
setVisible(true);
public void stop() {
setVisible(false);
private void LoginGUI() {
super.setSize(300, 150);
super.setBackground(Color.white);
lTitle = new JLabel("<HTML><BODY><FONT FACE = \"COURIER NEW\" SIZE = 6 COLOR = BLUE>Login</FONT></BODY></HTML>", JLabel.CENTER);
lUsername = new JLabel("Username : ", JLabel.CENTER);
lPassword = new JLabel("Password : ", JLabel.CENTER);
tUsername = new JTextField(15);
tPassword = new JPasswordField(15);
bLogin = new JButton("LOGIN");
// bLogin.setEnabled(false);
bLogin.addActionListener(this);
bLogin.addKeyListener(this);
panel2 = new JPanel();
GridBagLayout gbag = new GridBagLayout();
GridBagConstraints gbc = new GridBagConstraints();
panel2.setLayout(gbag);
panel2.addKeyListener(this);
gbc.anchor = GridBagConstraints.CENTER;
panel2.setMinimumSize(new Dimension(300, 200));
panel2.setMaximumSize(panel2.getMinimumSize());
panel2.setPreferredSize(panel2.getMinimumSize());
gbc.gridx = 1;
gbc.gridy = 1;
gbag.setConstraints(lUsername,gbc);
panel2.add(lUsername);
gbc.gridx = 2;
gbc.gridy = 1;
gbag.setConstraints(tUsername,gbc);
panel2.add(tUsername);
gbc.gridx = 1;
gbc.gridy = 2;
gbag.setConstraints(lPassword,gbc);
panel2.add(lPassword);
gbc.gridx = 2;
gbc.gridy = 2;
gbag.setConstraints(tPassword,gbc);
panel2.add(tPassword);
gbc.gridx = 2;
gbc.gridy = 3;
gbag.setConstraints(lEmpty,gbc);
panel2.add(lEmpty);
gbc.gridx = 2;
gbc.gridy = 4;
gbag.setConstraints(bLogin,gbc);
panel2.add(bLogin);
panel1 = new JPanel(new BorderLayout());
panel1.add(lTitle, BorderLayout.NORTH);
panel1.add(panel2, BorderLayout.CENTER);
add(panel1);
setVisible(true);
public void keyReleased(KeyEvent ke) {}
public void keyTyped(KeyEvent ke) {}
public void keyPressed(KeyEvent ke) {
if(ke.getKeyCode() == KeyEvent.VK_ENTER){
String username = tUsername.getText();
String password = new String(tPassword.getPassword());
if(username.length() == 0 || password.length() == 0) {
JOptionPane.showMessageDialog(new JFrame(),"You must enter a username and password to login", "Error", JOptionPane.ERROR_MESSAGE);
else {
boolean flag = checkUsernamePassword(username, password);
if(flag)
JOptionPane.showMessageDialog(new JFrame(),"Username and Password Accepted", "Access Granted", JOptionPane.INFORMATION_MESSAGE);
else
JOptionPane.showMessageDialog(new JFrame(),"Username or password Incorrect", "Access Denied", JOptionPane.INFORMATION_MESSAGE);
public void actionPerformed(ActionEvent ae) {
String gotCommand = ae.getActionCommand();
if(gotCommand.equals("LOGIN")) {
String username = tUsername.getText();
String password = new String(tPassword.getPassword());
if(username.length() == 0 || password.length() == 0) {
JOptionPane.showMessageDialog(new JFrame(),"You must enter a username and password to login", "Error", JOptionPane.ERROR_MESSAGE);
else {
boolean flag = checkUsernamePassword(username, password);
if(flag)
JOptionPane.showMessageDialog(new JFrame(),"Username and Password Accepted", "Access Granted", JOptionPane.INFORMATION_MESSAGE);
else
JOptionPane.showMessageDialog(new JFrame(),"Username or password Incorrect", "Access Denied", JOptionPane.INFORMATION_MESSAGE);
private boolean checkUsernamePassword(String username, String password) {
String user = null, pswd = null;
try {
FileInputStream fin = new FileInputStream("@data\\userpass.txt");
DataInputStream din = new DataInputStream(fin);
BufferedReader brin = new BufferedReader(new InputStreamReader(din));
user = (String) brin.readLine();
pswd = (String) brin.readLine();
catch(IOException ioe) {
ioe.printStackTrace();
if(username.equals(user) && password.equals(pswd))
return true;
else
return false;
}PLEASE HELP ME GUYS......RockAsh wrote:
Hey Andrew, first of all sorry for that shout, it was un-intentional as i am new to posting topics on forums and didn't new that this kind of writing is meant as shouting. Cool.
Secondly thank you for taking interest in my concern.No worries.
Thirdly, as i mentioned before, I am reading i file for checking of username and password. the file is named as "userpass.txt" and is saved in the directory named "@data" which is kept in the same directory in which my class file resides.OK - server-side. That makes some sense, and makes things easier. The problem with your current code is that the applet will be looking for that directory on the end user's local file system. Of course the file does not exist there, so the applet will fail unless the the end user is using the same machine as the server is coming from.
To get access to a resource on the server - the place the applet lives - requires an URL. In applets, URLs are relatively easy to form. It might be something along the lines of
URL urlToPswrd = new URL(getCodeBase(), "@data/userpass.txt");
InputStream is = urlToPswrd.openStream();
DataInputStream din = new DataInputStream(is);
So the problem is that it is reading the file and showing the specific output dialog box when i run it through appletviewer.. Huhh. What version of the SDK are you using? More recent applet viewers should report security exceptions if the File exists.
..but the same is not happening when i launch the applet in my browser window using the code as written belowHave you discovered how to open the Java Console in the browser yet? It is important.
Also the answer to your second question
Also, the entire approach to storing/restoring the password is potentially wrong. For instance, where is it supposed to be stored, on the server, or on the client?is that, as of now it is just my college project so all the data files and the username and password wiles will be stored on my laptop only i.e. on the client only. no server involved.OK, but understand that an applet ultimately does not make much sense unless deployed through a server. And the entire server/client distinction becomes very important, since that code would be searching for a non-existent file on the computer of the end user. -
COMMUNICATION BETWEEN JAVASCRIPT AND JAVA APPLET: US$20 AWARD FOR SOLUTION!
COMMUNICATION BETWEEN JAVASCRIPT AND JAVA APPLET PROBLEM (Easy Filter Java Applet) -
US$20 TO ANYONE WHO CAN RESOLVE THE PROBLEM
To forum visitors:
I am prepared to pay a standard shareware fee of US$20 to a user who can resolve this technical problem.
If your advice resolves the problem, I'll forward the payment to your postal address (include your
address with your reply, and also your email address)
I am attempting to enable a HTML button (using Javascript's onClick command) to directly input a number into one of the parameter text boxes in the Easy Filter Java applet (ie, enter a new color value number in the text field of the standard Colors Multiplicator Filter interface).
The applet is Freeware and can be downloaded at: http://www.javazoom.net/applets/easyfilter10/EasyFilter10.html
(It is a very effective bitmap display and editing utility)
To achieve this, I am trying to access the part of the applet that defines and sets the textbox. The text box is defined in the .class file by accessing the parameter details in the genericfilter.txt file (accompanies the .class files). I need to access 'private String appletInitialize()' and then one of the 'textFieldParameters' which sets the textbox.
I understand the basic syntax for referencing the applet:
document.appletname.setString("An example"). However, accessing the text fields in this applet is more complex!!
Please can you recommend the correct Javascript syntax to achieve communication with the applet.
Thank you for your kind assistance.
JM Graham
[email protected]
The Java source code for the applet: EasyFilter.class
# Easy Filter - E.B/JavaZOOM 1999 #
# Contact: [email protected] #
# http://javazoom.hypermart.net #
/* Originally compiled from EasyFilter.java */
import java.awt.*;
import java.io.*;
import java.net.*;
import java.applet.Applet;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.MemoryImageSource;
import java.awt.image.PixelGrabber;
import java.util.Vector;
public synchronized class EasyFilter extends Applet implements KeyListener
private String paramFileName;
private Color bgColor;
private Color fgColor;
private Color parColor;
private Color sepColor;
private Color titleColor;
private Color helpColor;
private int WinWidth;
private int WinHeight;
private String title;
private String logoFileName;
private String originalImageFileName;
private String filteredCaption;
private String originalCaption;
private Vector paramsName;
private Vector paramsValue;
private Vector paramsComment;
private Panel panelParameters[];
private Label labelParameters[];
private TextField textFieldParameters[];
private Label labelComments[];
private int nbParameters;
private ScrollPane scrollPaneParams;
private Panel panelParams;
private Image theLogo;
private Image theOriginalImage;
private Image theFilteredImage;
private int theOriginalPixelArray[];
private int logoWidth;
private int logoHeight;
private int imageWidth;
private int imageHeight;
private drawCanvas canvasTitle;
private Panel panelTitle;
private Label labelTitle;
private Panel panelImages;
private Panel panelOriginalImage;
private drawCanvas canvasOriginalImage;
private Label labelOriginalImage;
private Panel panelFilteredImage;
private drawCanvas canvasFilteredImage;
private Label labelFilteredImage;
private Panel panelHelp;
private Label labelHelp;
private int Yspc;
private FilterImplementation theFilter;
public void init()
String string = null;
string = appletInitialize();
setBackground(bgColor);
if (string != null)
removeAll();
setBackground(Color.white);
setForeground(Color.black);
Label label = new Label(new StringBuffer("Error: ").append(string).toString(), 1);
Panel panel = new Panel();
panel.add(label);
add(panel);
setLayout(new FlowLayout(1, 5, Yspc));
public void keyPressed(KeyEvent keyEvent)
panelHelp.removeAll();
boolean flag = true;
if (KeyEvent.getKeyText(keyEvent.getKeyCode()).equals("Enter"))
for (int i = 0; i < nbParameters; )
try
paramsValue.setElementAt(new Double(textFieldParameters.getText()), i);
i++;
catch (NumberFormatException e)
labelHelp.setText(labelParameters[i].getText() + ": Not a Number");
flag = false;
break;
if (flag == 1)
labelHelp.setText(" .... Running, please wait .... ");
labelHelp.setAlignment(1);
panelHelp.add(labelHelp);
panelHelp.doLayout();
theFilter.updateParameters(paramsValue);
theFilter.computeFilter();
theFilteredImage = createImage(new MemoryImageSource(theFilter.getFinalImageWidth(), theFilter.getFinalImageHeight(), theFilter.getFinalImageBuffer(), 0, theFilter.getFinalImageWidth()));
canvasFilteredImage.setImage(theFilteredImage);
canvasFilteredImage.setBounds(0, 0, theFilter.getFinalImageWidth(), theFilter.getFinalImageHeight());
canvasFilteredImage.repaint();
panelHelp.removeAll();
labelHelp.setText("- Done -");
else
labelHelp.setText("- Press Enter to run the Filter -");
labelHelp.setAlignment(1);
panelHelp.add(labelHelp);
panelHelp.doLayout();
public void keyReleased(KeyEvent keyEvent)
public void keyTyped(KeyEvent keyEvent)
private String appletInitialize()
WinWidth = size().width;
WinHeight = size().height;
if (getParameter("bgcolor") == null)
bgColor = new Color(0, 0, 40);
else
bgColor = new Color(Integer.parseInt(getParameter("bgcolor"), 16));
if (getParameter("fgcolor") == null)
fgColor = new Color(255, 255, 255);
else
fgColor = new Color(Integer.parseInt(getParameter("fgcolor"), 16));
if (getParameter("sepcolor") == null)
sepColor = new Color(158, 128, 128);
else
sepColor = new Color(Integer.parseInt(getParameter("sepcolor"), 16));
if (getParameter("parcolor") == null)
parColor = new Color(24, 24, 24);
else
parColor = new Color(Integer.parseInt(getParameter("parcolor"), 16));
if (getParameter("titlecolor") == null)
titleColor = new Color(255, 255, 0);
else
titleColor = new Color(Integer.parseInt(getParameter("titlecolor"), 16));
if (getParameter("helpcolor") == null)
helpColor = new Color(0, 255, 255);
else
helpColor = new Color(Integer.parseInt(getParameter("helpcolor"), 16));
paramsName = new Vector();
paramsValue = new Vector();
paramsComment = new Vector();
paramFileName = getParameter("paramfile");
String string = readParams(paramFileName);
if (string != null)
return string;
MediaTracker mediaTracker = new MediaTracker(this);
theOriginalImage = getImage(getDocumentBase(), originalImageFileName);
mediaTracker.addImage(theOriginalImage, 0);
if (logoFileName != null)
theLogo = getImage(getDocumentBase(), logoFileName);
mediaTracker.addImage(theLogo, 1);
try
mediaTracker.waitForAll();
catch (InterruptedException e1)
return "Error while loading image";
if (mediaTracker.isErrorAny())
return "Error while loading image";
if (logoFileName != null)
logoWidth = theLogo.getWidth(this);
logoHeight = theLogo.getHeight(this);
imageWidth = theOriginalImage.getWidth(this);
imageHeight = theOriginalImage.getHeight(this);
theOriginalPixelArray = new int[imageWidth * imageHeight];
PixelGrabber pixelGrabber = new PixelGrabber(theOriginalImage, 0, 0, imageWidth, imageHeight, theOriginalPixelArray, 0, imageWidth);
try
pixelGrabber.grabPixels();
panelTitle = new Panel();
canvasTitle = new drawCanvas();
labelTitle = new Label();
panelTitle.setLayout(new FlowLayout(1, 10, Yspc));
add(panelTitle);
panelTitle.setBackground(bgColor);
panelTitle.add(canvasTitle);
canvasTitle.setImage(theLogo);
canvasTitle.setBounds(0, 0, logoWidth, logoHeight);
labelTitle.setText(title);
catch (InterruptedException e2)
return "Internal Error, Try RELOAD !";
if (title != null)
panelTitle.add(labelTitle);
labelTitle.setForeground(titleColor);
labelTitle.setFont(new Font("Dialog", 1, 14));
panelImages = new Panel();
panelOriginalImage = new Panel();
canvasOriginalImage = new drawCanvas();
labelOriginalImage = new Label();
panelFilteredImage = new Panel();
canvasFilteredImage = new drawCanvas();
labelFilteredImage = new Label();
panelImages.setLayout(new FlowLayout(1, 10, Yspc));
add(panelImages);
panelImages.setBackground(bgColor);
panelOriginalImage.setLayout(new BorderLayout(0, 2));
panelImages.add(panelOriginalImage);
panelOriginalImage.setBackground(Color.black);
panelOriginalImage.add("Center", canvasOriginalImage);
canvasOriginalImage.setImage(theOriginalImage);
canvasOriginalImage.setBounds(0, 0, imageWidth, imageHeight);
labelOriginalImage.setText(originalCaption);
labelOriginalImage.setAlignment(1);
panelOriginalImage.add("South", labelOriginalImage);
labelOriginalImage.setBackground(Color.lightGray);
labelOriginalImage.setForeground(Color.black);
labelOriginalImage.setFont(new Font("SansSerif", 0, 10));
panelFilteredImage.setLayout(new BorderLayout(0, 2));
panelImages.add(panelFilteredImage);
panelFilteredImage.setBackground(Color.black);
panelFilteredImage.add("Center", canvasFilteredImage);
theFilter = new FilterImplementation(paramsValue, theOriginalPixelArray, imageWidth, imageHeight);
theFilter.computeFilter();
theFilteredImage = createImage(new MemoryImageSource(theFilter.getFinalImageWidth(), theFilter.getFinalImageHeight(), theFilter.getFinalImageBuffer(), 0, theFilter.getFinalImageWidth()));
canvasFilteredImage.setImage(theFilteredImage);
canvasFilteredImage.setBounds(0, 0, theFilter.getFinalImageWidth(), theFilter.getFinalImageHeight());
labelFilteredImage.setText(filteredCaption);
labelFilteredImage.setAlignment(1);
panelFilteredImage.add("South", labelFilteredImage);
labelFilteredImage.setBackground(Color.lightGray);
labelFilteredImage.setFont(new Font("SansSerif", 0, 10));
scrollPaneParams = new ScrollPane(0);
panelParams = new Panel();
nbParameters = paramsName.size();
int i = WinHeight - (33 + 7 * Yspc + logoHeight + imageHeight + 23);
if (i < Yspc + 2 + 24)
i = Yspc + 2 + 24;
scrollPaneParams.setBounds(0, 0, WinWidth - 10, i);
panelParams.setLayout(new GridLayout(nbParameters, 1, 5, Yspc / 2));
scrollPaneParams.add(panelParams);
panelParams.setBackground(sepColor);
panelParameters = new Panel[nbParameters];
labelParameters = new Label[nbParameters];
textFieldParameters = new TextField[nbParameters];
labelComments = new Label[nbParameters];
for (int j = 0; j < nbParameters; j++)
panelParameters[j] = new Panel();
panelParameters[j].setLayout(new FlowLayout(0, 5, 1));
panelParams.add(panelParameters[j]);
panelParameters[j].setBackground(parColor);
labelParameters[j] = new Label();
labelParameters[j].setText((String)paramsName.elementAt(j));
panelParameters[j].add(labelParameters[j]);
labelParameters[j].setForeground(fgColor);
labelParameters[j].setFont(new Font("Dialog", 1, 12));
textFieldParameters[j] = new TextField(8);
textFieldParameters[j].setText(paramsValue.elementAt(j).toString());
panelParameters[j].add(textFieldParameters[j]);
textFieldParameters[j].setBackground(fgColor);
textFieldParameters[j].addKeyListener(this);
labelComments[j] = new Label();
labelComments[j].setText((String)paramsComment.elementAt(j));
panelParameters[j].add(labelComments[j]);
labelComments[j].setForeground(fgColor);
add(scrollPaneParams);
panelHelp = new Panel();
labelHelp = new Label();
panelHelp.setLayout(new FlowLayout(1, 5, 0));
add(panelHelp);
panelHelp.setBackground(bgColor);
labelHelp.setText(" Change colour values and press enter ");
labelHelp.setAlignment(1);
panelHelp.add(labelHelp);
labelHelp.setForeground(helpColor);
return null;
private String readParams(String string1)
Object object1;
String string2;
if (string1 == null)
return "Filename of filter's parameters needed";
try
URL uRL = new URL(getDocumentBase(), string1);
URLConnection uRLConnection = uRL.openConnection();
uRLConnection.setDoInput(true);
uRLConnection.setUseCaches(false);
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(uRLConnection.getInputStream()));
string2 = null;
catch ()
return object1.getMessage();
catch ()
return object1.getMessage();
catch ()
return object1.getMessage();
if (bufferedReader != null)
Object object2;
try
for (object2 = bufferedReader.readLine(); object2 != null && string2 == null; object2 = bufferedReader.readLine())
string2 = extractFormat(object2);
catch ()
string2 = object2.getMessage();
finally
bufferedReader.close();
if (string2 != null)
return string2;
else
return null;
private String extractFormat(String string1)
if (string1.length() == 0)
return null;
int i = 0;
int j = string1.indexOf(" ", i);
if (j == -1)
return "Bad format error (space missing)";
String string2 = string1.substring(i, j);
if (string2.equals("TITLE"))
i = j;
j = string1.indexOf(34, i);
if (j == -1)
return "Bad format (Double quote in TITLE missing)";
i = j + 1;
j = string1.indexOf(34, i);
if (j == -1)
return "Bad format (Double quote in TITLE missing)";
title = string1.substring(i, j);
return null;
if (string2.equals("ORIGINALCAPTION"))
i = j;
j = string1.indexOf(34, i);
if (j == -1)
return "Bad format (Double quote in ORIGINALCAPTION missing)";
i = j + 1;
j = string1.indexOf(34, i);
if (j == -1)
return "Bad format (Double quote in ORIGINALCAPTION missing)";
originalCaption = string1.substring(i, j);
return null;
if (string2.equals("FILTEREDCAPTION"))
i = j;
j = string1.indexOf(34, i);
if (j == -1)
return "Bad format (Double quote in FILTEREDCAPTION missing)";
i = j + 1;
j = string1.indexOf(34, i);
if (j == -1)
return "Bad format (Double quote in FILTEREDCAPTION missing)";
filteredCaption = string1.substring(i, j);
return null;
if (string2.equals("LOGO"))
i = j + 1;
j = string1.length();
logoFileName = string1.substring(i, j);
return null;
if (string2.equals("ORIGINALIMAGE"))
i = j + 1;
j = string1.length();
originalImageFileName = string1.substring(i, j);
return null;
if (!string2.equals("PARAM"))
return null;
i = j;
j = string1.indexOf(34, i);
if (j == -1)
return "Bad format in a PARAM line";
i = j + 1;
j = string1.indexOf(34, i);
if (j == -1)
return "Bad format in a PARAM line";
paramsName.addElement(string1.substring(i, j));
i = j + 2;
j = string1.indexOf(32, i);
if (j == -1)
return "Bad format in a PARAM line";
try
paramsValue.addElement(new Double(string1.substring(i, j)));
j = string1.indexOf(34, i);
catch (NumberFormatException e)
return "Bad format in a PARAM line";
if (j == -1)
return "Bad format (Double quote in PARAM comment missing)";
i = j + 1;
j = string1.indexOf(34, i);
if (j == -1)
return "Bad format (Double quote in PARAM comment missing)";
paramsComment.addElement(string1.substring(i, j));
return null;
public EasyFilter()
logoHeight = 33;
Yspc = 5;Addition to my above submission
To clarify, I'll offer the US$20 to the FIRST person who offers me a workable solution to the problem, not to everyone!!!
JMGRAHAM -
How to add a scrollbar to applet
This is the source code of my applet.I wat to have an autoscroll on this applet
i think it is usefull if i put here all the code for my project.
======================================================
Class ConsolePanel:
The file defines a class ConsolePanel. Objects of type
ConsolePanel can be used for simple input/output exchanges with
the user. Various routines are provided for reading and writing
values of various types from the output. (This class gives all
the I/O behavior of another class, Console, that represents a
separate window for doing console-style I/O.)
This class is dependent on another class, ConsoleCanvas.
Note that when the console has the input focus, it is outlined with
a bright blue border. If, in addition, the console is waiting for
user input, then there will be a blinking cursor. If the console
is not outlined in light blue, the user has to click on it before
any input will be accepted.
This is an update an earlier version of the same class,
rewritten to use realToString() for output of floating point
numbers..
package myproj;
import java.awt.*;
import java.awt.event.*;
import javax.swing.JScrollPane;
import javax.swing.JScrollBar;
import javax.swing.*;
public class ConsolePanel extends JTextArea{
static public JScrollPane scrollPane;
// ***************************** Constructors *******************************
public ConsolePanel() { // default constructor just provides default window title and size
setBackground(Color.white);
setLayout(new BorderLayout(0, 0));
canvas = new ConsoleCanvas(500,1000);
scrollPane = new JScrollPane(canvas);
scrollPane.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setPreferredSize( new Dimension( 1000,10000) );
add("Center", scrollPane);
//scrollPane.getVerticalScrollBar().setUnitIncrement(1);
try {
jbInit();
} catch (Exception ex) {
ex.printStackTrace();
public void clear() { // clear all characters from the canvas
canvas.clear();
// *************************** I/O Methods *********************************
// Methods for writing the primitive types, plus type String,
// to the console window, with no extra spaces.
// Note that the real-number data types, float
// and double, a rounded version is output that will
// use at most 10 or 11 characters. If you want to
// output a real number with full accuracy, use
// "con.put(String.valueOf(x))", for example.
public void put(int x) {
put(x, 0);
} // Note: also handles byte and short!
public void put(long x) {
put(x, 0);
public void put(double x) {
put(x, 0);
} // Also handles float.
public void put(char x) {
put(x, 0);
public void put(boolean x) {
put(x, 0);
public void put(String x) {
put(x, 0);
// Methods for writing the primitive types, plus type String,
// to the console window,followed by a carriage return, with
// no extra spaces.
public void putln(int x) {
put(x, 0);
newLine();
} // Note: also handles byte and short!
public void putln(long x) {
put(x, 0);
newLine();
public void putln(double x) {
put(x, 0);
newLine();
} // Also handles float.
public void putln(char x) {
put(x, 0);
newLine();
public void putln(boolean x) {
put(x, 0);
newLine();
public void putln(String x) {
put(x, 0);
newLine();
// Methods for writing the primitive types, plus type String,
// to the console window, with a minimum field width of w,
// and followed by a carriage return.
// If outut value is less than w characters, it is padded
// with extra spaces in front of the value.
public void putln(int x, int w) {
put(x, w);
newLine();
} // Note: also handles byte and short!
public void putln(long x, int w) {
put(x, w);
newLine();
public void putln(double x, int w) {
put(x, w);
newLine();
} // Also handles float.
public void putln(char x, int w) {
put(x, w);
newLine();
public void putln(boolean x, int w) {
put(x, w);
newLine();
public void putln(String x, int w) {
put(x, w);
newLine();
// Method for outputting a carriage return
public void putln() {
newLine();
// Methods for writing the primitive types, plus type String,
// to the console window, with minimum field width w.
public void put(int x, int w) {
dumpString(String.valueOf(x), w);
} // Note: also handles byte and short!
public void put(long x, int w) {
dumpString(String.valueOf(x), w);
public void put(double x, int w) {
dumpString(realToString(x), w);
} // Also handles float.
public void put(char x, int w) {
dumpString(String.valueOf(x), w);
public void put(boolean x, int w) {
dumpString(String.valueOf(x), w);
public void put(String x, int w) {
dumpString(x, w);
// Methods for reading in the primitive types, plus "words" and "lines".
// The "getln..." methods discard any extra input, up to and including
// the next carriage return.
// A "word" read by getlnWord() is any sequence of non-blank characters.
// A "line" read by getlnString() or getln() is everything up to next CR;
// the carriage return is not part of the returned value, but it is
// read and discarded.
// Note that all input methods except getAnyChar(), peek(), the ones for lines
// skip past any blanks and carriage returns to find a non-blank value.
// getln() can return an empty string; getChar() and getlnChar() can
// return a space or a linefeed ('\n') character.
// peek() allows you to look at the next character in input, without
// removing it from the input stream. (Note that using this
// routine might force the user to enter a line, in order to
// check what the next character.)
// Acceptable boolean values are the "words": true, false, t, f, yes,
// no, y, n, 0, or 1; uppercase letters are OK.
// None of these can produce an error; if an error is found in input,
// the user is forced to re-enter.
// Available input routines are:
// getByte() getlnByte() getShort() getlnShort()
// getInt() getlnInt() getLong() getlnLong()
// getFloat() getlnFloat() getDouble() getlnDouble()
// getChar() getlnChar() peek() getAnyChar()
// getWord() getlnWord() getln() getString() getlnString()
// (getlnString is the same as getln and is onlyprovided for consistency.)
public byte getlnByte() {
byte x = getByte();
emptyBuffer();
return x;
public short getlnShort() {
short x = getShort();
emptyBuffer();
return x;
public int getlnInt() {
int x = getInt();
emptyBuffer();
return x;
public long getlnLong() {
long x = getLong();
emptyBuffer();
return x;
public float getlnFloat() {
float x = getFloat();
emptyBuffer();
return x;
public double getlnDouble() {
double x = getDouble();
emptyBuffer();
return x;
public char getlnChar() {
char x = getChar();
emptyBuffer();
return x;
public boolean getlnBoolean() {
boolean x = getBoolean();
emptyBuffer();
return x;
public String getlnWord() {
String x = getWord();
emptyBuffer();
return x;
public String getlnString() {
return getln();
} // same as getln()
public String getln() {
StringBuffer s = new StringBuffer(100);
char ch = readChar();
while (ch != '\n') {
s.append(ch);
ch = readChar();
return s.toString();
public byte getByte() {
return (byte) readInteger( -128L, 127L);
public short getShort() {
return (short) readInteger( -32768L, 32767L);
public int getInt() {
return (int) readInteger((long) Integer.MIN_VALUE,
(long) Integer.MAX_VALUE);
public long getLong() {
return readInteger(Long.MIN_VALUE, Long.MAX_VALUE);
public char getAnyChar() {
return readChar();
public char peek() {
return lookChar();
public char getChar() { // skip spaces & cr's, then return next char
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
return readChar();
public float getFloat() { // can return positive or negative infinity
float x = 0.0F;
while (true) {
String str = readRealString();
if (str.equals("")) {
errorMessage("Illegal floating point input.",
"Real number in the range " + Float.MIN_VALUE +
" to " + Float.MAX_VALUE);
} else {
Float f = null;
try {
f = Float.valueOf(str);
} catch (NumberFormatException e) {
errorMessage("Illegal floating point input.",
"Real number in the range " + Float.MIN_VALUE +
" to " + Float.MAX_VALUE);
continue;
if (f.isInfinite()) {
errorMessage("Floating point input outside of legal range.",
"Real number in the range " + Float.MIN_VALUE +
" to " + Float.MAX_VALUE);
continue;
x = f.floatValue();
break;
return x;
public double getDouble() {
double x = 0.0;
while (true) {
String str = readRealString();
if (str.equals("")) {
errorMessage("Illegal floating point input",
"Real number in the range " + Double.MIN_VALUE +
" to " + Double.MAX_VALUE);
} else {
Double f = null;
try {
f = Double.valueOf(str);
} catch (NumberFormatException e) {
errorMessage("Illegal floating point input",
"Real number in the range " + Double.MIN_VALUE +
" to " + Double.MAX_VALUE);
continue;
if (f.isInfinite()) {
errorMessage("Floating point input outside of legal range.",
"Real number in the range " + Double.MIN_VALUE +
" to " + Double.MAX_VALUE);
continue;
x = f.doubleValue();
break;
return x;
public String getWord() {
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
StringBuffer str = new StringBuffer(50);
while (ch != ' ' && ch != '\n') {
str.append(readChar());
ch = lookChar();
return str.toString();
public boolean getBoolean() {
boolean ans = false;
while (true) {
String s = getWord();
if (s.equalsIgnoreCase("true") || s.equalsIgnoreCase("t") ||
s.equalsIgnoreCase("yes") || s.equalsIgnoreCase("y") ||
s.equals("1")) {
ans = true;
break;
} else if (s.equalsIgnoreCase("false") || s.equalsIgnoreCase("f") ||
s.equalsIgnoreCase("no") || s.equalsIgnoreCase("n") ||
s.equals("0")) {
ans = false;
break;
} else {
errorMessage("Illegal boolean input value.",
"one of: true, false, t, f, yes, no, y, n, 0, or 1");
return ans;
// ***************** Everything beyond this point is private *******************
// ********************** Utility routines for input/output ********************
private ConsoleCanvas canvas; // the canvas where I/O is displayed
private String buffer = null; // one line read from input
private int pos = 0; // position next char in input line that has
// not yet been processed
private String readRealString() { // read chars from input following syntax of real numbers
StringBuffer s = new StringBuffer(50);
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
if (ch == '-' || ch == '+') {
s.append(readChar());
ch = lookChar();
while (ch == ' ') {
readChar();
ch = lookChar();
} while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
if (ch == '.') {
s.append(readChar());
ch = lookChar();
while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
if (ch == 'E' || ch == 'e') {
s.append(readChar());
ch = lookChar();
if (ch == '-' || ch == '+') {
s.append(readChar());
ch = lookChar();
} while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
return s.toString();
private long readInteger(long min, long max) { // read long integer, limited to specified range
long x = 0;
while (true) {
StringBuffer s = new StringBuffer(34);
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
if (ch == '-' || ch == '+') {
s.append(readChar());
ch = lookChar();
while (ch == ' ') {
readChar();
ch = lookChar();
} while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
if (s.equals("")) {
errorMessage("Illegal integer input.",
"Integer in the range " + min + " to " + max);
} else {
String str = s.toString();
try {
x = Long.parseLong(str);
} catch (NumberFormatException e) {
errorMessage("Illegal integer input.",
"Integer in the range " + min + " to " + max);
continue;
if (x < min || x > max) {
errorMessage("Integer input outside of legal range.",
"Integer in the range " + min + " to " + max);
continue;
break;
return x;
private static String realToString(double x) {
// Goal is to get a reasonable representation of x in at most
// 10 characters, or 11 characters if x is negative.
if (Double.isNaN(x)) {
return "undefined";
if (Double.isInfinite(x)) {
if (x < 0) {
return "-INF";
} else {
return "INF";
if (Math.abs(x) <= 5000000000.0 && Math.rint(x) == x) {
return String.valueOf((long) x);
String s = String.valueOf(x);
if (s.length() <= 10) {
return s;
boolean neg = false;
if (x < 0) {
neg = true;
x = -x;
s = String.valueOf(x);
if (x >= 0.00005 && x <= 50000000 &&
(s.indexOf('E') == -1 && s.indexOf('e') == -1)) { // trim x to 10 chars max
s = round(s, 10);
s = trimZeros(s);
} else if (x > 1) { // construct exponential form with positive exponent
long power = (long) Math.floor(Math.log(x) / Math.log(10));
String exp = "E" + power;
int numlength = 10 - exp.length();
x = x / Math.pow(10, power);
s = String.valueOf(x);
s = round(s, numlength);
s = trimZeros(s);
s += exp;
} else { // constuct exponential form
long power = (long) Math.ceil( -Math.log(x) / Math.log(10));
String exp = "E-" + power;
int numlength = 10 - exp.length();
x = x * Math.pow(10, power);
s = String.valueOf(x);
s = round(s, numlength);
s = trimZeros(s);
s += exp;
if (neg) {
return "-" + s;
} else {
return s;
private static String trimZeros(String num) { // used by realToString
if (num.indexOf('.') >= 0 && num.charAt(num.length() - 1) == '0') {
int i = num.length() - 1;
while (num.charAt(i) == '0') {
i--;
if (num.charAt(i) == '.') {
num = num.substring(0, i);
} else {
num = num.substring(0, i + 1);
return num;
private static String round(String num, int length) { // used by realToString
if (num.indexOf('.') < 0) {
return num;
if (num.length() <= length) {
return num;
if (num.charAt(length) >= '5' && num.charAt(length) != '.') {
char[] temp = new char[length + 1];
int ct = length;
boolean rounding = true;
for (int i = length - 1; i >= 0; i--) {
temp[ct] = num.charAt(i);
if (rounding && temp[ct] != '.') {
if (temp[ct] < '9') {
temp[ct]++;
rounding = false;
} else {
temp[ct] = '0';
ct--;
if (rounding) {
temp[ct] = '1';
ct--;
// ct is -1 or 0
return new String(temp, ct + 1, length - ct);
} else {
return num.substring(0, length);
private void dumpString(String str, int w) { // output string to console
for (int i = str.length(); i < w; i++) {
canvas.addChar(' ');
for (int i = 0; i < str.length(); i++) {
if ((int) str.charAt(i) >= 0x20 && (int) str.charAt(i) != 0x7F) { // no control chars or delete
canvas.addChar(str.charAt(i));
} else if (str.charAt(i) == '\n' || str.charAt(i) == '\r') {
newLine();
private void errorMessage(String message, String expecting) {
// inform user of error and force user to re-enter.
newLine();
dumpString(" *** Error in input: " + message + "\n", 0);
dumpString(" *** Expecting: " + expecting + "\n", 0);
dumpString(" *** Discarding Input: ", 0);
if (lookChar() == '\n') {
dumpString("(end-of-line)\n\n", 0);
} else {
while (lookChar() != '\n') {
canvas.addChar(readChar());
dumpString("\n\n", 0);
dumpString("Please re-enter: ", 0);
readChar(); // discard the end-of-line character
private char lookChar() { // return next character from input
if (buffer == null || pos > buffer.length()) {
fillBuffer();
if (pos == buffer.length()) {
return '\n';
return buffer.charAt(pos);
private char readChar() { // return and discard next character from input
char ch = lookChar();
pos++;
return ch;
private void newLine() { // output a CR to console
canvas.addCR();
private void fillBuffer() { // Wait for user to type a line and press return,
// and put the typed line into the buffer.
buffer = canvas.readLine();
pos = 0;
private void emptyBuffer() { // discard the rest of the current line of input
buffer = null;
public void clearBuffers() { // I expect this will only be called by
// CanvasApplet when a program ends. It should
// not be called in the middle of a running program.
buffer = null;
canvas.clearTypeAhead();
private void jbInit() throws Exception {
this.setNextFocusableComponent(scrollPane);
this.setToolTipText("");
} // end of class Console
============================================================
Class ConsoleCanvas:
/* A class that implements basic console-oriented input/output, for use with
Console.java and ConsolePanel.java. This class provides the basic character IO.
Higher-leve fucntions (reading and writing numbers, booleans, etc) are provided
in Console.java and ConolePanel.java.
(This vesion of ConsoleCanvas is an udate of an earilier version, rewritten to
be compliand with Java 1.1. David Eck; July 17, 1998.)
(Modified August 16, 1998 to add the
a mousePressed method to ConsoleCanvas. The mousePressed method requests
the focus. This is necessary for Sun's Java implementation -- though not,
apparently for anyone else's. Also added: an isFocusTraversable() method)
MouseListener interface and
Minor modifications, February 9, 2000, some glitches in the graphics.
package myproj;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ConsoleCanvas extends JTextArea implements FocusListener, KeyListener,
MouseListener {
// public interface, constructor and methods
public ConsoleCanvas(int u,int y) {
addFocusListener(this);
addKeyListener(this);
try {
jbInit();
} catch (Exception ex) {
ex.printStackTrace();
public final String readLine() { // wait for user to enter a line of input;
// Line can only contain characters in the range
// ' ' to '~'.
return doReadLine();
public final void addChar(char ch) { // output PRINTABLE character to console
putChar(ch);
public final void addCR() { // add a CR to the console
putCR();
public synchronized void clear() { // clear console and return cursor to row 0, column 0.
if (OSC == null) {
return;
currentRow = 0;
currentCol = 0;
OSCGraphics.setColor(Color.white);
OSCGraphics.fillRect(4, 4, getSize().width - 8, getSize().height - 8);
OSCGraphics.setColor(Color.black);
repaint();
try {
Thread.sleep(25);
} catch (InterruptedException e) {}
// focus and key event handlers; not meant to be called excpet by system
public void keyPressed(KeyEvent evt) {
doKey(evt.getKeyChar());
public void keyReleased(KeyEvent evt) {}
public void keyTyped(KeyEvent evt) {}
public void focusGained(FocusEvent evt) {
doFocus(true);
public void focusLost(FocusEvent evt) {
doFocus(false);
public boolean isFocusTraversable() {
// Allows the user to move the focus to the canvas
// by pressing the tab key.
return true;
// Mouse listener methods -- here just to make sure that the canvas
// gets the focuse when the user clicks on it. These are meant to
// be called only by the system.
public void mousePressed(MouseEvent evt) {
requestFocus();
public void mouseReleased(MouseEvent evt) {}
public void mouseClicked(MouseEvent evt) {}
public void mouseEntered(MouseEvent evt) {}
public void mouseExited(MouseEvent evt) {}
// implementation section: protected variables and methods.
protected StringBuffer typeAhead = new StringBuffer();
// Characters typed by user but not yet processed;
// User can "type ahead" the charcters typed until
// they are needed to satisfy a readLine.
protected final int maxLineLength = 256;
// No lines longer than this are returned by readLine();
// The system effectively inserts a CR after 256 chars
// of input without a carriage return.
protected int rows, columns; // rows and columns of chars in the console
protected int currentRow, currentCol; // current curson position
protected Font font; // Font used in console (Courier); All font
// data is set up in the doSetup() method.
protected int lineHeight; // height of one line of text in the console
protected int baseOffset; // distance from top of a line to its baseline
protected int charWidth; // width of a character (constant, since a monospaced font is used)
protected int leading; // space between lines
protected int topOffset; // distance from top of console to top of text
protected int leftOffset; // distance from left of console to first char on line
protected Image OSC; // off-screen backup for console display (except cursor)
protected Graphics OSCGraphics; // graphics context for OSC
protected boolean hasFocus = false; // true if this canvas has the input focus
protected boolean cursorIsVisible = false; // true if cursor is currently visible
private int pos = 0; // exists only for sharing by next two methods
public synchronized void clearTypeAhead() {
// clears any unprocessed user typing. This is meant only to
// be called by ConsolePanel, when a program being run by
// console Applet ends. But just to play it safe, pos is
// set to -1 as a signal to doReadLine that it should return.
typeAhead.setLength(0);
pos = -1;
notify();
protected synchronized String doReadLine() { // reads a line of input, up to next CR
if (OSC == null) { // If this routine is called before the console has
// completely opened, we shouldn't procede; give the
// window a chance to open, so that paint() can call doSetup().
try {
wait(5000);
} catch (InterruptedException e) {} // notify() should be set by doSetup()
if (OSC == null) { // If nothing has happened for 5 seconds, we are probably in
// trouble, but when the heck, try calling doSetup and proceding anyway.
doSetup();
if (!hasFocus) { // Make sure canvas has input focus
requestFocus();
StringBuffer lineBuffer = new StringBuffer(); // buffer for constructing line from user
pos = 0;
while (true) { // Read and process chars from the typeAhead buffer until a CR is found.
while (pos >= typeAhead.length()) { // If the typeAhead buffer is empty, wait for user to type something
cursorBlink();
try {
wait(500);
} catch (InterruptedException e) {}
if (pos == -1) { // means clearTypeAhead was called;
return ""; // this is an abnormal return that should not happen
if (cursorIsVisible) {
cursorBlink();
if (typeAhead.charAt(pos) == '\r' || typeAhead.charAt(pos) == '\n') {
putCR();
pos++;
break;
if (typeAhead.charAt(pos) == 8 || typeAhead.charAt(pos) == 127) {
if (lineBuffer.length() > 0) {
lineBuffer.setLength(lineBuffer.length() - 1);
eraseChar();
pos++;
} else if (typeAhead.charAt(pos) >= ' ' &&
typeAhead.charAt(pos) < 127) {
putChar(typeAhead.charAt(pos));
lineBuffer.append(typeAhead.charAt(pos));
pos++;
} else {
pos++;
if (lineBuffer.length() == maxLineLength) {
putCR();
pos = typeAhead.length();
break;
if (pos >= typeAhead.length()) { // delete all processed chars from typeAhead
typeAhead.setLength(0);
} else {
int len = typeAhead.length();
for (int i = pos; i < len; i++) {
typeAhead.setCharAt(i - pos, typeAhead.charAt(i));
typeAhead.setLength(len - pos);
return lineBuffer.toString(); // return the string that was entered
protected synchronized void doKey(char ch) { // process key pressed by user
typeAhead.append(ch);
notify();
private void putCursor(Graphics g) { // draw the cursor
g.drawLine(leftOffset + currentCol * charWidth + 1,
topOffset + (currentRow * lineHeight),
leftOffset + currentCol * charWidth + 1,
topOffset + (currentRow * lineHeight + baseOffset));
protected synchronized void putChar(char ch) { // draw ch at cursor position and move cursor
if (OSC == null) { // If this routine is called before the console has
// completely opened, we shouldn't procede; give the
// window a chance to open, so that paint() can call doSetup().
try {
wait(5000);
} catch (InterruptedException e) {} // notify() should be set by doSetup()
if (OSC == null) { // If nothing has happened for 5 seconds, we are probably in
// trouble, but when the heck, try calling doSetup and proceding anyway.
doSetup();
if (currentCol >= columns) {
putCR();
currentCol++;
Graphics g = getGraphics();
g.setColor(Color.black);
g.setFont(font);
char[] fudge = new char[1];
fudge[0] = ch;
g.drawChars(fudge, 0, 1, leftOffset + (currentCol - 1) * charWidth,
topOffset + currentRow * lineHeight + baseOffset);
g.dispose();
OSCGraphics.drawChars(fudge, 0, 1,
leftOffset + (currentCol - 1) * charWidth,
topOffset + currentRow * lineHeight + baseOffset);
protected void eraseChar() { // erase char before cursor position and move cursor
if (currentCol == 0 && currentRow == 0) {
return;
currentCol--;
if (currentCol < 0) {
currentRow--;
currentCol = columns - 1;
Graphics g = getGraphics();
g.setColor(Color.white);
g.fillRect(leftOffset + (currentCol * charWidth),
topOffset + (currentRow * lineHeight),
charWidth, lineHeight - 1);
g.dispose();
OSCGraphics.setColor(Color.white);
OSCGraphics.fillRect(leftOffset + (currentCol * charWidth),
topOffset + (currentRow * lineHeight),
charWidth, lineHeight - 1);
OSCGraphics.setColor(Color.black);
protected synchronized void putCR() { // move cursor to start of next line, scrolling window if necessary
if (OSC == null) { // If this routine is called before the console has
// completely opened, we shouldn't procede; give the
// window a chance to open, so that paint() can call doSetup().
try {
wait(5000);
} catch (InterruptedException e) {} // notify() should be set by doSetup()
if (OSC == null) { // If nothing has happened for 5 seconds, we are probably in
// trouble, but when the heck, try calling doSetup and proceding anyway.
doSetup();
currentCol = 0;
currentRow++;
if (currentRow < rows) {
return;
OSCGraphics.copyArea(leftOffset, topOffset + lineHeight,
columns * charWidth,
(rows - 1) * lineHeight - leading, 0, -lineHeight);
OSCGraphics.setColor(Color.white);
OSCGraphics.fillRect(leftOffset, topOffset + (rows - 1) * lineHeight,
columns * charWidth, lineHeight - leading);
OSCGraphics.setColor(Color.black);
currentRow = rows - 1;
Graphics g = getGraphics();
paint(g);
g.dispose();
try {
Thread.sleep(20);
} catch (InterruptedException e) {}
protected void cursorBlink() { // toggle visibility of cursor (but don't show it if focus has been lost)
if (cursorIsVisible) {
Graphics g = getGraphics();
g.setColor(Color.white);
putCursor(g);
cursorIsVisible = false;
g.dispose();
} else if (hasFocus) {
Graphics g = getGraphics();
g.setColor(Color.black);
putCursor(g);
cursorIsVisible = true;
g.dispose();
protected synchronized void doFocus(boolean focus) { // react to gain or loss of focus
if (OSC == null) {
doSetup();
hasFocus = focus;
if (hasFocus) { // the rest of the routine draws or erases border around canvas
OSCGraphics.setColor(Color.cyan);
} else {
OSCGraphics.setColor(Color.white);
int w = getSize().width;
int h = getSize().height;
for (int i = 0; i < 3; i++) {
OSCGraphics.drawRect(i, i, w - 2 * i, h - 2 * i);
OSCGraphics.drawLine(0, h - 3, w, h - 3);
OSCGraphics.drawLine(w - 3, 0, w - 3, h);
OSCGraphics.setColor(Color.black);
repaint();
try {
Thread.sleep(50);
} catch (InterruptedException e) {}
notify();
protected void doSetup() { // get font parameters and create OSC
int w = getSize().width;
int h = getSize().height;
font = new Font("Courier", Font.PLAIN, getFont().getSize());
FontMetrics fm = getFontMetrics(font);
lineHeight = fm.getHeight();
leading = fm.getLeading();
baseOffset = fm.getAscent();
charWidth = fm.charWidth('W');
columns = (w - 12) / charWidth;
rows = (h - 12 + leading) / lineHeight;
leftOffset = (w - columns * charWidth) / 2;
topOffset = (h + leading - rows * lineHeight) / 2;
OSC = createImage(w, h);
OSCGraphics = OSC.getGraphics();
OSCGraphics.setFont(font);
OSCGraphics.setColor(Color.white);
OSCGraphics.fillRect(0, 0, w, h);
OSCGraphics.setColor(Color.black);
notify();
public void update(Graphics g) {
paint(g);
public synchronized void paint(Graphics g) {
if (OSC == null) {
doSetup();
g.drawImage(OSC, 0, 0, this);
private void jbInit() throws Exception {
===============================================================
and finally Consola:
package myproj;
/* The Consola provides a basis for writing applets that simulate
line-oriented consola-type input/output. The class ConsoleCanvas is
used to provide the I/O routines; these routines type output into
the ConsoleCanvas and read input typed there by the user. See the
files CanvasPanel.java and ConsoleCanvas.java for information.
A consola applet is set up to run one particular program. The applet
includes a button that the user presses to run the program (or to
abort it when it is running). It also includes a label, which by default
is "Java I/O consola". The default program, defined in this file,
is a simple Hello World program.
To write a new consola applet, with a more interesting program, you
should create a subclass of Consola. The subclass should
override the method program() , which represents the program to
be run. The program should use the instance variable, consola, to
do input/output. For example, consola.putln("HelloWorld.")
or N=consola.getInt(). All the public methods of class ConsolePanel
can be called in the program.
(Of course, you could also just modify this file, instead of
writing a subclass.)
import java.awt.*;
import java.awt.event.*;
import myproj.ConsoleCanvas;
import myproj.ConsolePanel;
import java.util.*;
import javax.swing.JScrollPane;
import javax.swing.JList;
import javax.swing.*;
import java.io.*;
public class Consola extends java.applet.Applet implements Runnable,
ActionListener {
public Consola() {
try {
jbInit();
} catch (Exception ex) {
ex.printStackTrace();
protected String title = "Configure Vlan "; // (Used for compatibility with previous versions of consola Applet)
protected String getTitle() {
// Return a label to appears over the consola;
// If you want to change the label, override this
// method to return a different string.
return title;
//variabilele mele
static String[] Foo={"Fa0/1","Fa0/2","Fa0/3","Fa0/4","Fa0/5","Fa0/6","Fa0/7","Fa0/8","Fa0/9","F a0/10","Fa0/11","Fa0/12"};
static String[] vlan={"","","","","","","","","","","",""};
static String [] showdefault={"","","","","","","","","","","",""};
statFirst thing...you made a mistake
import javax.swing.JScrollPane;
import javax.swing.JScrollBar;
import javax.swing.*;When you import javax.swing.*; You automatically
import JScrollPane & JScrollBar class, there's no
need for you to re import again...
That is not always a mistake. There are cases where it makes sense to do both (i.e., to import both '*' and a specific class name from that package at the same time). I believe the common example is:
import java.awt.*;
import java.util.*;
import java.util.List;Now you can use "List" as a short name for "java.util.List", but must use "java.awt.List" in full for "java.awt.List" objects. If you just did:
import java.awt.*;
import java.util.*;Then you couldn't use List as a short name for anything--because it is ambiguous. You'd have to use both "java.awt.List" and "java.util.List" spelled out in full.
Or, if you did:
import java.awt.*;
import java.util.*;
import java.awt.List; // NOTE CHANGEThen "List" is short for "java.awt.List", and you must use "java.util.List" in full for "java.awt.List" objects. -
Help With adding a scrollbar to my applet
This is the source code of my applet.I wat to have an autoscroll on this applet
i think it is usefull if i put here all the code for my project.
======================================================
Class ConsolePanel:
The file defines a class ConsolePanel. Objects of type
ConsolePanel can be used for simple input/output exchanges with
the user. Various routines are provided for reading and writing
values of various types from the output. (This class gives all
the I/O behavior of another class, Console, that represents a
separate window for doing console-style I/O.)
This class is dependent on another class, ConsoleCanvas.
Note that when the console has the input focus, it is outlined with
a bright blue border. If, in addition, the console is waiting for
user input, then there will be a blinking cursor. If the console
is not outlined in light blue, the user has to click on it before
any input will be accepted.
This is an update an earlier version of the same class,
rewritten to use realToString() for output of floating point
numbers..
package myproj;
import java.awt.*;
import java.awt.event.*;
import javax.swing.JScrollPane;
import javax.swing.JScrollBar;
import javax.swing.*;
public class ConsolePanel extends JTextArea{
static public JScrollPane scrollPane;
// ***************************** Constructors *******************************
public ConsolePanel() { // default constructor just provides default window title and size
setBackground(Color.white);
setLayout(new BorderLayout(0, 0));
canvas = new ConsoleCanvas(500,1000);
scrollPane = new JScrollPane(canvas);
scrollPane.setVerticalScrollBarPolicy(
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setPreferredSize( new Dimension( 1000,10000) );
add("Center", scrollPane);
//scrollPane.getVerticalScrollBar().setUnitIncrement(1);
try {
jbInit();
} catch (Exception ex) {
ex.printStackTrace();
public void clear() { // clear all characters from the canvas
canvas.clear();
// *************************** I/O Methods *********************************
// Methods for writing the primitive types, plus type String,
// to the console window, with no extra spaces.
// Note that the real-number data types, float
// and double, a rounded version is output that will
// use at most 10 or 11 characters. If you want to
// output a real number with full accuracy, use
// "con.put(String.valueOf(x))", for example.
public void put(int x) {
put(x, 0);
} // Note: also handles byte and short!
public void put(long x) {
put(x, 0);
public void put(double x) {
put(x, 0);
} // Also handles float.
public void put(char x) {
put(x, 0);
public void put(boolean x) {
put(x, 0);
public void put(String x) {
put(x, 0);
// Methods for writing the primitive types, plus type String,
// to the console window,followed by a carriage return, with
// no extra spaces.
public void putln(int x) {
put(x, 0);
newLine();
} // Note: also handles byte and short!
public void putln(long x) {
put(x, 0);
newLine();
public void putln(double x) {
put(x, 0);
newLine();
} // Also handles float.
public void putln(char x) {
put(x, 0);
newLine();
public void putln(boolean x) {
put(x, 0);
newLine();
public void putln(String x) {
put(x, 0);
newLine();
// Methods for writing the primitive types, plus type String,
// to the console window, with a minimum field width of w,
// and followed by a carriage return.
// If outut value is less than w characters, it is padded
// with extra spaces in front of the value.
public void putln(int x, int w) {
put(x, w);
newLine();
} // Note: also handles byte and short!
public void putln(long x, int w) {
put(x, w);
newLine();
public void putln(double x, int w) {
put(x, w);
newLine();
} // Also handles float.
public void putln(char x, int w) {
put(x, w);
newLine();
public void putln(boolean x, int w) {
put(x, w);
newLine();
public void putln(String x, int w) {
put(x, w);
newLine();
// Method for outputting a carriage return
public void putln() {
newLine();
// Methods for writing the primitive types, plus type String,
// to the console window, with minimum field width w.
public void put(int x, int w) {
dumpString(String.valueOf(x), w);
} // Note: also handles byte and short!
public void put(long x, int w) {
dumpString(String.valueOf(x), w);
public void put(double x, int w) {
dumpString(realToString(x), w);
} // Also handles float.
public void put(char x, int w) {
dumpString(String.valueOf(x), w);
public void put(boolean x, int w) {
dumpString(String.valueOf(x), w);
public void put(String x, int w) {
dumpString(x, w);
// Methods for reading in the primitive types, plus "words" and "lines".
// The "getln..." methods discard any extra input, up to and including
// the next carriage return.
// A "word" read by getlnWord() is any sequence of non-blank characters.
// A "line" read by getlnString() or getln() is everything up to next CR;
// the carriage return is not part of the returned value, but it is
// read and discarded.
// Note that all input methods except getAnyChar(), peek(), the ones for lines
// skip past any blanks and carriage returns to find a non-blank value.
// getln() can return an empty string; getChar() and getlnChar() can
// return a space or a linefeed ('\n') character.
// peek() allows you to look at the next character in input, without
// removing it from the input stream. (Note that using this
// routine might force the user to enter a line, in order to
// check what the next character.)
// Acceptable boolean values are the "words": true, false, t, f, yes,
// no, y, n, 0, or 1; uppercase letters are OK.
// None of these can produce an error; if an error is found in input,
// the user is forced to re-enter.
// Available input routines are:
// getByte() getlnByte() getShort() getlnShort()
// getInt() getlnInt() getLong() getlnLong()
// getFloat() getlnFloat() getDouble() getlnDouble()
// getChar() getlnChar() peek() getAnyChar()
// getWord() getlnWord() getln() getString() getlnString()
// (getlnString is the same as getln and is onlyprovided for consistency.)
public byte getlnByte() {
byte x = getByte();
emptyBuffer();
return x;
public short getlnShort() {
short x = getShort();
emptyBuffer();
return x;
public int getlnInt() {
int x = getInt();
emptyBuffer();
return x;
public long getlnLong() {
long x = getLong();
emptyBuffer();
return x;
public float getlnFloat() {
float x = getFloat();
emptyBuffer();
return x;
public double getlnDouble() {
double x = getDouble();
emptyBuffer();
return x;
public char getlnChar() {
char x = getChar();
emptyBuffer();
return x;
public boolean getlnBoolean() {
boolean x = getBoolean();
emptyBuffer();
return x;
public String getlnWord() {
String x = getWord();
emptyBuffer();
return x;
public String getlnString() {
return getln();
} // same as getln()
public String getln() {
StringBuffer s = new StringBuffer(100);
char ch = readChar();
while (ch != '\n') {
s.append(ch);
ch = readChar();
return s.toString();
public byte getByte() {
return (byte) readInteger( -128L, 127L);
public short getShort() {
return (short) readInteger( -32768L, 32767L);
public int getInt() {
return (int) readInteger((long) Integer.MIN_VALUE,
(long) Integer.MAX_VALUE);
public long getLong() {
return readInteger(Long.MIN_VALUE, Long.MAX_VALUE);
public char getAnyChar() {
return readChar();
public char peek() {
return lookChar();
public char getChar() { // skip spaces & cr's, then return next char
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
return readChar();
public float getFloat() { // can return positive or negative infinity
float x = 0.0F;
while (true) {
String str = readRealString();
if (str.equals("")) {
errorMessage("Illegal floating point input.",
"Real number in the range " + Float.MIN_VALUE +
" to " + Float.MAX_VALUE);
} else {
Float f = null;
try {
f = Float.valueOf(str);
} catch (NumberFormatException e) {
errorMessage("Illegal floating point input.",
"Real number in the range " + Float.MIN_VALUE +
" to " + Float.MAX_VALUE);
continue;
if (f.isInfinite()) {
errorMessage("Floating point input outside of legal range.",
"Real number in the range " + Float.MIN_VALUE +
" to " + Float.MAX_VALUE);
continue;
x = f.floatValue();
break;
return x;
public double getDouble() {
double x = 0.0;
while (true) {
String str = readRealString();
if (str.equals("")) {
errorMessage("Illegal floating point input",
"Real number in the range " + Double.MIN_VALUE +
" to " + Double.MAX_VALUE);
} else {
Double f = null;
try {
f = Double.valueOf(str);
} catch (NumberFormatException e) {
errorMessage("Illegal floating point input",
"Real number in the range " + Double.MIN_VALUE +
" to " + Double.MAX_VALUE);
continue;
if (f.isInfinite()) {
errorMessage("Floating point input outside of legal range.",
"Real number in the range " + Double.MIN_VALUE +
" to " + Double.MAX_VALUE);
continue;
x = f.doubleValue();
break;
return x;
public String getWord() {
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
StringBuffer str = new StringBuffer(50);
while (ch != ' ' && ch != '\n') {
str.append(readChar());
ch = lookChar();
return str.toString();
public boolean getBoolean() {
boolean ans = false;
while (true) {
String s = getWord();
if (s.equalsIgnoreCase("true") || s.equalsIgnoreCase("t") ||
s.equalsIgnoreCase("yes") || s.equalsIgnoreCase("y") ||
s.equals("1")) {
ans = true;
break;
} else if (s.equalsIgnoreCase("false") || s.equalsIgnoreCase("f") ||
s.equalsIgnoreCase("no") || s.equalsIgnoreCase("n") ||
s.equals("0")) {
ans = false;
break;
} else {
errorMessage("Illegal boolean input value.",
"one of: true, false, t, f, yes, no, y, n, 0, or 1");
return ans;
// ***************** Everything beyond this point is private *******************
// ********************** Utility routines for input/output ********************
private ConsoleCanvas canvas; // the canvas where I/O is displayed
private String buffer = null; // one line read from input
private int pos = 0; // position next char in input line that has
// not yet been processed
private String readRealString() { // read chars from input following syntax of real numbers
StringBuffer s = new StringBuffer(50);
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
if (ch == '-' || ch == '+') {
s.append(readChar());
ch = lookChar();
while (ch == ' ') {
readChar();
ch = lookChar();
} while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
if (ch == '.') {
s.append(readChar());
ch = lookChar();
while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
if (ch == 'E' || ch == 'e') {
s.append(readChar());
ch = lookChar();
if (ch == '-' || ch == '+') {
s.append(readChar());
ch = lookChar();
} while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
return s.toString();
private long readInteger(long min, long max) { // read long integer, limited to specified range
long x = 0;
while (true) {
StringBuffer s = new StringBuffer(34);
char ch = lookChar();
while (ch == ' ' || ch == '\n') {
readChar();
if (ch == '\n') {
dumpString("? ", 0);
ch = lookChar();
if (ch == '-' || ch == '+') {
s.append(readChar());
ch = lookChar();
while (ch == ' ') {
readChar();
ch = lookChar();
} while (ch >= '0' && ch <= '9') {
s.append(readChar());
ch = lookChar();
if (s.equals("")) {
errorMessage("Illegal integer input.",
"Integer in the range " + min + " to " + max);
} else {
String str = s.toString();
try {
x = Long.parseLong(str);
} catch (NumberFormatException e) {
errorMessage("Illegal integer input.",
"Integer in the range " + min + " to " + max);
continue;
if (x < min || x > max) {
errorMessage("Integer input outside of legal range.",
"Integer in the range " + min + " to " + max);
continue;
break;
return x;
private static String realToString(double x) {
// Goal is to get a reasonable representation of x in at most
// 10 characters, or 11 characters if x is negative.
if (Double.isNaN(x)) {
return "undefined";
if (Double.isInfinite(x)) {
if (x < 0) {
return "-INF";
} else {
return "INF";
if (Math.abs(x) <= 5000000000.0 && Math.rint(x) == x) {
return String.valueOf((long) x);
String s = String.valueOf(x);
if (s.length() <= 10) {
return s;
boolean neg = false;
if (x < 0) {
neg = true;
x = -x;
s = String.valueOf(x);
if (x >= 0.00005 && x <= 50000000 &&
(s.indexOf('E') == -1 && s.indexOf('e') == -1)) { // trim x to 10 chars max
s = round(s, 10);
s = trimZeros(s);
} else if (x > 1) { // construct exponential form with positive exponent
long power = (long) Math.floor(Math.log(x) / Math.log(10));
String exp = "E" + power;
int numlength = 10 - exp.length();
x = x / Math.pow(10, power);
s = String.valueOf(x);
s = round(s, numlength);
s = trimZeros(s);
s += exp;
} else { // constuct exponential form
long power = (long) Math.ceil( -Math.log(x) / Math.log(10));
String exp = "E-" + power;
int numlength = 10 - exp.length();
x = x * Math.pow(10, power);
s = String.valueOf(x);
s = round(s, numlength);
s = trimZeros(s);
s += exp;
if (neg) {
return "-" + s;
} else {
return s;
private static String trimZeros(String num) { // used by realToString
if (num.indexOf('.') >= 0 && num.charAt(num.length() - 1) == '0') {
int i = num.length() - 1;
while (num.charAt(i) == '0') {
i--;
if (num.charAt(i) == '.') {
num = num.substring(0, i);
} else {
num = num.substring(0, i + 1);
return num;
private static String round(String num, int length) { // used by realToString
if (num.indexOf('.') < 0) {
return num;
if (num.length() <= length) {
return num;
if (num.charAt(length) >= '5' && num.charAt(length) != '.') {
char[] temp = new char[length + 1];
int ct = length;
boolean rounding = true;
for (int i = length - 1; i >= 0; i--) {
temp[ct] = num.charAt(i);
if (rounding && temp[ct] != '.') {
if (temp[ct] < '9') {
temp[ct]++;
rounding = false;
} else {
temp[ct] = '0';
ct--;
if (rounding) {
temp[ct] = '1';
ct--;
// ct is -1 or 0
return new String(temp, ct + 1, length - ct);
} else {
return num.substring(0, length);
private void dumpString(String str, int w) { // output string to console
for (int i = str.length(); i < w; i++) {
canvas.addChar(' ');
for (int i = 0; i < str.length(); i++) {
if ((int) str.charAt(i) >= 0x20 && (int) str.charAt(i) != 0x7F) { // no control chars or delete
canvas.addChar(str.charAt(i));
} else if (str.charAt(i) == '\n' || str.charAt(i) == '\r') {
newLine();
private void errorMessage(String message, String expecting) {
// inform user of error and force user to re-enter.
newLine();
dumpString(" *** Error in input: " + message + "\n", 0);
dumpString(" *** Expecting: " + expecting + "\n", 0);
dumpString(" *** Discarding Input: ", 0);
if (lookChar() == '\n') {
dumpString("(end-of-line)\n\n", 0);
} else {
while (lookChar() != '\n') {
canvas.addChar(readChar());
dumpString("\n\n", 0);
dumpString("Please re-enter: ", 0);
readChar(); // discard the end-of-line character
private char lookChar() { // return next character from input
if (buffer == null || pos > buffer.length()) {
fillBuffer();
if (pos == buffer.length()) {
return '\n';
return buffer.charAt(pos);
private char readChar() { // return and discard next character from input
char ch = lookChar();
pos++;
return ch;
private void newLine() { // output a CR to console
canvas.addCR();
private void fillBuffer() { // Wait for user to type a line and press return,
// and put the typed line into the buffer.
buffer = canvas.readLine();
pos = 0;
private void emptyBuffer() { // discard the rest of the current line of input
buffer = null;
public void clearBuffers() { // I expect this will only be called by
// CanvasApplet when a program ends. It should
// not be called in the middle of a running program.
buffer = null;
canvas.clearTypeAhead();
private void jbInit() throws Exception {
this.setNextFocusableComponent(scrollPane);
this.setToolTipText("");
} // end of class Console
============================================================
Class ConsoleCanvas:
/* A class that implements basic console-oriented input/output, for use with
Console.java and ConsolePanel.java. This class provides the basic character IO.
Higher-leve fucntions (reading and writing numbers, booleans, etc) are provided
in Console.java and ConolePanel.java.
(This vesion of ConsoleCanvas is an udate of an earilier version, rewritten to
be compliand with Java 1.1. David Eck; July 17, 1998.)
(Modified August 16, 1998 to add the
a mousePressed method to ConsoleCanvas. The mousePressed method requests
the focus. This is necessary for Sun's Java implementation -- though not,
apparently for anyone else's. Also added: an isFocusTraversable() method)
MouseListener interface and
Minor modifications, February 9, 2000, some glitches in the graphics.
package myproj;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ConsoleCanvas extends JTextArea implements FocusListener, KeyListener,
MouseListener {
// public interface, constructor and methods
public ConsoleCanvas(int u,int y) {
addFocusListener(this);
addKeyListener(this);
try {
jbInit();
} catch (Exception ex) {
ex.printStackTrace();
public final String readLine() { // wait for user to enter a line of input;
// Line can only contain characters in the range
// ' ' to '~'.
return doReadLine();
public final void addChar(char ch) { // output PRINTABLE character to console
putChar(ch);
public final void addCR() { // add a CR to the console
putCR();
public synchronized void clear() { // clear console and return cursor to row 0, column 0.
if (OSC == null) {
return;
currentRow = 0;
currentCol = 0;
OSCGraphics.setColor(Color.white);
OSCGraphics.fillRect(4, 4, getSize().width - 8, getSize().height - 8);
OSCGraphics.setColor(Color.black);
repaint();
try {
Thread.sleep(25);
} catch (InterruptedException e) {}
// focus and key event handlers; not meant to be called excpet by system
public void keyPressed(KeyEvent evt) {
doKey(evt.getKeyChar());
public void keyReleased(KeyEvent evt) {}
public void keyTyped(KeyEvent evt) {}
public void focusGained(FocusEvent evt) {
doFocus(true);
public void focusLost(FocusEvent evt) {
doFocus(false);
public boolean isFocusTraversable() {
// Allows the user to move the focus to the canvas
// by pressing the tab key.
return true;
// Mouse listener methods -- here just to make sure that the canvas
// gets the focuse when the user clicks on it. These are meant to
// be called only by the system.
public void mousePressed(MouseEvent evt) {
requestFocus();
public void mouseReleased(MouseEvent evt) {}
public void mouseClicked(MouseEvent evt) {}
public void mouseEntered(MouseEvent evt) {}
public void mouseExited(MouseEvent evt) {}
// implementation section: protected variables and methods.
protected StringBuffer typeAhead = new StringBuffer();
// Characters typed by user but not yet processed;
// User can "type ahead" the charcters typed until
// they are needed to satisfy a readLine.
protected final int maxLineLength = 256;
// No lines longer than this are returned by readLine();
// The system effectively inserts a CR after 256 chars
// of input without a carriage return.
protected int rows, columns; // rows and columns of chars in the console
protected int currentRow, currentCol; // current curson position
protected Font font; // Font used in console (Courier); All font
// data is set up in the doSetup() method.
protected int lineHeight; // height of one line of text in the console
protected int baseOffset; // distance from top of a line to its baseline
protected int charWidth; // width of a character (constant, since a monospaced font is used)
protected int leading; // space between lines
protected int topOffset; // distance from top of console to top of text
protected int leftOffset; // distance from left of console to first char on line
protected Image OSC; // off-screen backup for console display (except cursor)
protected Graphics OSCGraphics; // graphics context for OSC
protected boolean hasFocus = false; // true if this canvas has the input focus
protected boolean cursorIsVisible = false; // true if cursor is currently visible
private int pos = 0; // exists only for sharing by next two methods
public synchronized void clearTypeAhead() {
// clears any unprocessed user typing. This is meant only to
// be called by ConsolePanel, when a program being run by
// console Applet ends. But just to play it safe, pos is
// set to -1 as a signal to doReadLine that it should return.
typeAhead.setLength(0);
pos = -1;
notify();
protected synchronized String doReadLine() { // reads a line of input, up to next CR
if (OSC == null) { // If this routine is called before the console has
// completely opened, we shouldn't procede; give the
// window a chance to open, so that paint() can call doSetup().
try {
wait(5000);
} catch (InterruptedException e) {} // notify() should be set by doSetup()
if (OSC == null) { // If nothing has happened for 5 seconds, we are probably in
// trouble, but when the heck, try calling doSetup and proceding anyway.
doSetup();
if (!hasFocus) { // Make sure canvas has input focus
requestFocus();
StringBuffer lineBuffer = new StringBuffer(); // buffer for constructing line from user
pos = 0;
while (true) { // Read and process chars from the typeAhead buffer until a CR is found.
while (pos >= typeAhead.length()) { // If the typeAhead buffer is empty, wait for user to type something
cursorBlink();
try {
wait(500);
} catch (InterruptedException e) {}
if (pos == -1) { // means clearTypeAhead was called;
return ""; // this is an abnormal return that should not happen
if (cursorIsVisible) {
cursorBlink();
if (typeAhead.charAt(pos) == '\r' || typeAhead.charAt(pos) == '\n') {
putCR();
pos++;
break;
if (typeAhead.charAt(pos) == 8 || typeAhead.charAt(pos) == 127) {
if (lineBuffer.length() > 0) {
lineBuffer.setLength(lineBuffer.length() - 1);
eraseChar();
pos++;
} else if (typeAhead.charAt(pos) >= ' ' &&
typeAhead.charAt(pos) < 127) {
putChar(typeAhead.charAt(pos));
lineBuffer.append(typeAhead.charAt(pos));
pos++;
} else {
pos++;
if (lineBuffer.length() == maxLineLength) {
putCR();
pos = typeAhead.length();
break;
if (pos >= typeAhead.lengHi
I don't understand the exact need you want
you want to add Scrolling facility to your Entire Applet or only for the Textarea Class?
In first case
Create the ScrollPane and add it to the applet contentPane. and put entire components to a Panel and just add it to scroll pane.
Regards
Vinoth
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