NoClassDefFoundError

[Leeish]

Been working on this one for a bit to no avail. I followed a tutorial online just to get familiar with different concepts. All of this worked and I had a nice little sprite animation moving on my screen no flickering etc. Perfect.

Then I tried to move a lot of my code to a Core class that would be extended from my main class. Not working but I have no idea why. I followed the tutorial for this part as well and I am getting a NoClassDefFoundError and as I can tell from reading this comes from members being available at compile time but not run time.

I have changed no settings, libs, paths, etc. Nothing, only code.

Here is my main class...

package game;
import java.awt.*;
import java.awt.event.*;

public class Game extends Core implements KeyListener {
    public static void main(String[] args) {
        new Game().run();
    }
    
    private String mess = "";
    
   //init also call init from superclass
   public void init(){
       super.init();
       Window w = screen.getFullScreenWindow();
       w.setFocusTraversalKeysEnabled(false);
       w.addKeyListener(this);
       mess="press escape to exit";
       
   }
   
   //Key Pressed
   public void keyPressed(KeyEvent e){
       int keyCode = e.getKeyCode();
       if(keyCode == KeyEvent.VK_ESCAPE){
           stop();
       } else {
           mess = "You Pressed : "+ KeyEvent.getKeyText(keyCode);
           e.consume();
       }
   }
   
   //Key Released
   public void keyReleased(KeyEvent e){
       int keyCode = e.getKeyCode();
       mess = "You Released : "+ KeyEvent.getKeyText(keyCode);
       e.consume();
   }
   
   //Last Method from interface
   public void keyTyped(KeyEvent e){
       e.consume();
   }
   
   //draw
   public synchronized void draw(Graphics2D g){
       Window w = screen.getFullScreenWindow();
       g.setColor(w.getBackground());
       g.fillRect(0, 0, screen.getWidth(), screen.getHeight());
       g.setColor(w.getForeground());
       g.drawString(mess, 200, 200);
   }
}

Here is the Core

package game;

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

public class Core {
    
    private static final DisplayMode modes[] = {
        new DisplayMode(800,600,32,0),
        new DisplayMode(800,600,24,0),
        new DisplayMode(800,600,16,0),
        new DisplayMode(640,480,32,0),
        new DisplayMode(640,480,24,0),
        new DisplayMode(640,480,16,0)
    };
    
    private boolean running;
    protected ScreenManager screen;
    
    //Stop Method
    public void stop(){
        running = false;
    }
    
    //Call int and Gameloop
    public void run(){
        try{
            init();
            gameLoop();
        }finally{
            screen.restoreScreen();
        }
    }
    
    //Set to Full Screen
    public void init(){
        screen = new ScreenManager();
        DisplayMode dm = screen.findFirstCompatibleMode(modes);
        screen.setFullScreen(dm);
        
        Window w = screen.getFullScreenWindow();
        w.setFont(new Font("Arial", Font.PLAIN,20));
        w.setBackground(Color.GREEN);
        w.setForeground(Color.WHITE);
        running = true;
    }
    
    //Main Game Loop
    public void gameLoop(){
        long startTime = System.currentTimeMillis();
        long cumTime = startTime;
        
        while(running){
            long timePassed = System.currentTimeMillis() - cumTime;
            cumTime += timePassed;
            
            update(timePassed);
            
            Graphics2D g = screen.getGraphics();
            draw(g);
            g.dispose();
            screen.update();
            
            try{
                Thread.sleep(20);
            }catch(Exception ex){}
        }
    }
    
    //Update Animation to be Overidden
    public void update(long timePassed){
    }
    
    //Update Draw to be Overidden
    public void draw(Graphics2D g){
    }
}

Here is the Screen Manager

package game;

import java.awt.*;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.lang.reflect.InvocationTargetException;
import javax.swing.JFrame;

//Buffer Strategy to get rid of flickering
//Rewrite Screen Class
public class ScreenManager {
    
    private GraphicsDevice vc;
    
    
    //Give VC access to monitor (Screen)
    public ScreenManager(){
        GraphicsEnvironment e = GraphicsEnvironment.getLocalGraphicsEnvironment();
        vc = e.getDefaultScreenDevice();
    }
    
    //get all compatible DM
    public DisplayMode[] getCompatibleDisplaymodes(){
        return vc.getDisplayModes();
    }
    
    //compares DM passed in to vc DM and see if they match
    public DisplayMode findFirstCompatibleMode(DisplayMode[] modes){
        DisplayMode goodModes[] = vc.getDisplayModes();
        for(int x = 0;x<modes.length;x++){
            for(int y = 0;y<goodModes.length;y++){
                if(displayModesMatch(modes[x], goodModes[y])){
                    return modes[x];
                }
            }
        }
        return null;
    }
    
    //Get Current DM
    public DisplayMode getCurrentDisplayMode(){
        return vc.getDisplayMode();
    }
    
    //Compare Display Modes
    public boolean displayModesMatch(DisplayMode m1, DisplayMode m2){
        if(m1.getHeight() != m2.getHeight() || m1.getWidth() != m2.getWidth()){
            return false;
        }
        if (m1.getRefreshRate() != DisplayMode.REFRESH_RATE_UNKNOWN && m1.getRefreshRate() != m2.getRefreshRate() && m2.getRefreshRate() != DisplayMode.REFRESH_RATE_UNKNOWN){
            return false;
        }
        if (m1.getBitDepth() != DisplayMode.BIT_DEPTH_MULTI && m1.getBitDepth() != m2.getBitDepth() && m2.getBitDepth() != DisplayMode.BIT_DEPTH_MULTI){
            return false;
        }
        return true;
    }
    
    //Make Frame Full Scree
    public void setFullScreen(DisplayMode dm){
        JFrame f = new JFrame();
        f.setUndecorated(true);
        f.setIgnoreRepaint(true);
        f.setResizable(false);
        vc.setFullScreenWindow(f);
        
        if(dm != null && vc.isDisplayChangeSupported()){
            try{
                vc.setDisplayMode(dm);
            }catch(Exception ex){}
        }
        f.createBufferStrategy(2);
    }
    
    //Set Graphics Object equal to this
    public Graphics2D getGraphics(){
        Window w = vc.getFullScreenWindow();
        if(w != null){
            BufferStrategy s = w.getBufferStrategy();
            return (Graphics2D)s.getDrawGraphics();
        }else {
            return null;
        }
    }
    
    //Updates Display
    public void update(){
        Window w = vc.getFullScreenWindow();
        if (w != null){
            BufferStrategy s = w.getBufferStrategy();
            if(!s.contentsLost()){
                s.show();
            }
        }
    }
    
    //Return Full Screen Window
    public Window getFullScreenWindow(){
        return vc.getFullScreenWindow();
    }
    
    //Get Width of Window
    public int getWidth(){
        Window w = vc.getFullScreenWindow();
        if (w != null){
            return w.getWidth();
        }else {
            return 0;
        }
    }
    
    //Get Height of Window
    public int getHeight(){
        Window w = vc.getFullScreenWindow();
        if (w != null){
            return w.getHeight();
        }else {
            return 0;
        }
    }
    
    //Exit Full Screen
    public void restoreScreen(){
        Window w = vc.getFullScreenWindow();
        if(w != null){
            w.dispose();
        }
        vc.setFullScreenWindow(null);
    }
    
    //Create image compatible with your monitor
    public BufferedImage createCompatibleImage(int w, int h, int t){
        Window win = vc.getFullScreenWindow();
        if(win != null){
            GraphicsConfiguration gc = win.getGraphicsConfiguration();
            return gc.createCompatibleImage(w, h, t);
        } else {
            return null;
        }
    }
}

I don't think I need to include the Animation or sprite as the error is as follows.

run:
Exception in thread "main" java.lang.NoClassDefFoundError: game/ScreenManager
	at game.Core.run(Core.java:31)
	at game.Game.main(Game.java:7)
Java Result: 1
BUILD SUCCESSFUL (total time: 1 second)

Core line 31 is | screen.restoreScreen();
main line 7 is | new Game().run();


Argh... what is wrong. The problem seems to come when I extended Core from Game, but I thought the guy in the video was doing that. Can you not extend your main Class.

Does Core have to be my main class and then I extend stuff from that?

[DeNiS_M]

OK so your classes all belong to the game package.
So your classes should be in: /somewhere/in/your/system/game
To compile them use javac like you normally would do.
To run them though you should be one directory higher (/somewhere/in/your/system/) and there invoke the java command with the cp option pointing to your working directory
and the full name of your class like this game.Game.

Hope i helped :)

[Norm]

Can you describe the folders the class files are in and what the current directory and classpath are when you issue the java command?
Is there a ScreenManager.class file in the games folder? Does the classpath point to the folder containing the game folder?

[Leeish]

I am using NetBeans IDE to create and run the entire thing. I never had to create/organize folders. However everything is in:


C:\Documents and Settings\admin\My Documents\NetBeansProjects\Game\src\game
Listed Files:
Animation, Core, Game, KeyTest, MainOld, Screen, ScreenManager, Sprite, SpriteOld

I was digging through and for some reason in the folder

C:\Documents and Settings\admin\My Documents\NetBeansProjects\Game\build\classes\game
Listed Files:
Animation$oneScene
Animation
Core
Game
Keytest
SpriteOld

ScreenManager does not exist. Where the F did it go? Didn't it have to have been there before when the app was running fine? I am guessing the \build\classes\game files are populated upon build time and because the ScreenManager class isn't in there, it's not being built. Am I right, and if so, now what.

I don't know the dir/classpath when issueing the java command because I just run build/play via NetBeans not from cmd prompt or anything.

[Norm]

Try going to the classes folder and entering the command:
java -cp . games.Game

Otherwise ask someone how to configure your IDE.

[Leeish]

Ok, so dumb/strange, I went to the properties of the application and under Source Package Folders there is only one listed... the src folder.
I added the src/game folder and ran the app and got the same compile error.

I removed that thing that i just added... and it works now... No clue, makes no sense. Sounds like a NetBeans glitch.

[Norm]

IDEs are wonderfully magical.

[Leeish]

So is Michael Vick who broke his hand and is costing me my fantasy game. Thanks for the help everyone.

[Tolls]

Ok, so dumb/strange, I went to the properties of the application and under Source Package Folders there is only one listed... the src folder.
I added the src/game folder and ran the app and got the same compile error.

That's because game si not a src folder...it's a package.
The source folder is the folder containing your packages (in your case src).

But...by doing that I suspect you forced Netbeans to recompile everything hence:

I removed that thing that i just added... and it works now... No clue, makes no sense. Sounds like a NetBeans glitch.

I would bet you didn't force a rebuild when you made your big changes, so Netbeans didn't bother compilig the ScreenManager.
Generally with IDEs it's a good idea to clean and build if you make some significant structural changes, since they can lose track of what needs recompiling.

[Leeish]

So when I run my app through the IDE even though it builds it, it doesn't necessarily build everything just what it thinks it needs to. But if I run the clean build it will force everything?

[Tolls]

Pretty much.
Some IDEs can lose track of what needs building.