Not sure what is wrong with this code?? Please help

I am learning java from videos online, I wont post the link because i'm not sure if I would be allows but I can do if anybody wants.

From the video I have copied the code exactly. My code compiles but when I run it, it doesn't work. The person online runs his and it works. No idea what's wrong:

I am using practicing using sprites:

Sprite class:

Code :

---

import java.awt.Image;
 
public class Sprite {
 
    private Animation a;
    private float x;
    private float y;
    private float vx;
    private float vy;
 
    //Constructor    
    public Sprite(Animation a)
    {
        this.a = a;
    }
 
    //Chnage position
    public void update(long timePassed)
    {
        x += vx * timePassed;
        y += vy * timePassed;
        a.update(timePassed);
    }
 
    //Get x position
    public float getX()
    {
        return x;
    }
 
    //Get y position
    public float getY()
    {
        return y;
    }
 
    //Set sprite x position
    public void setX(float x)
    {
        this.x = 0;
    }
 
    //Set sprite y position
    public void setY(float y)
    {
        this.y = 0;
    }
 
    //Get sprite width
    public int getWidth()
    {
        return a.getImage().getWidth(null);
    }
 
    //Get sprite height
    public int getHeight()
    {
        return a.getImage().getHeight(null);
    }
 
    //get horizontal velocity
    public float getVelocityX()
    {
        return vx;
    }
 
    //get vertical velocity
    public float getVelocityY()
    {
        return vy;
    }
 
    //set horizontal velocity
    public void setVelocityX(float vx)
    {
        this.vx = vx;
    }
 
    //set vertical velocity
    public void setVelocityY(float vy)
    {
        this.vy = vy;
    }
 
    //get sprite / image
    public Image getImage()
    {
        return a.getImage();
    }
 
}

---

Animation class:

Code :

---

import java.awt.Image;
import java.util.ArrayList;
 
public class Animation{
 
    private ArrayList scenes;
    private int sceneIndex;
    private long movieTime;
    private long totalTime;
 
    //CONSTRUCTOR
    public Animation(){
        scenes = new ArrayList();
        totalTime = 0;
        start();
    }
 
    //Add scene to ArrayList and set time for each scene
    public synchronized void addScene(Image i, long t)
    {
        totalTime += t;
        scenes.add(new oneScene(i, totalTime));
    }
 
    //Start aimation from begining
    public synchronized void start()
    {
        movieTime = 0;
        sceneIndex = 0;
    }
 
    //Change scenes
    public synchronized void update(long timePassed)
    {
        if(scenes.size()>1){
            movieTime += timePassed;
            if(movieTime >= totalTime){
                movieTime = 0;
                sceneIndex = 0;
            }
            while(movieTime > getScene(sceneIndex).endTime){
                sceneIndex++;
            }
        }
    }
 
    //get animations current scene AKA image
    public synchronized Image getImage()
    {
        if(scenes.size()==0){
            return null;
        }else{
            return getScene(sceneIndex).pic;
        }
    }
 
    //get scene
    private oneScene getScene(int x)
    {
        return (oneScene) scenes.get(x);
    }
 
    //Private inner class//
 
    private class oneScene{
        Image pic;
        long endTime;
 
        public oneScene(Image pic, long endTime)
        {
            this.pic = pic;
            this.endTime = endTime;
        }
    }
}

---

Screen Manager class:

Code :

---

 
import java.awt.*;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.lang.reflect.InvocationTargetException;
import javax.swing.JFrame;
 
public class ScreenManager {
 
    private GraphicsDevice vc;
 
    //Give vc acces to moniter screen
    public ScreenManager()
    {
        GraphicsEnvironment e = GraphicsEnvironment.getLocalGraphicsEnvironment();
        vc = e.getDefaultScreenDevice();
    }
 
    //Get all compatible display modes
    public DisplayMode[] getCompatibleDisaplyModes()
    {
        return vc.getDisplayModes();
    }
 
    //Compares display modes passed in to vc display modes 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 displayMode
    public DisplayMode getCurrentDisplayMode()
    {
        return vc.getDisplayMode();
    }
 
    //Checks if two modes match each other
    public boolean displayModesMatch(DisplayMode m1, DisplayMode m2)
    {
        if(m1.getWidth() != m2.getWidth() || m1.getHeight() != m2.getHeight())
        {
            return false;
        }
        if(m1.getBitDepth() != DisplayMode.BIT_DEPTH_MULTI && m2.getBitDepth() != DisplayMode.BIT_DEPTH_MULTI && m1.getBitDepth() != m2.getBitDepth())
        {
            return false;
        }
        if(m1.getRefreshRate() != DisplayMode.REFRESH_RATE_UNKNOWN && m2.getRefreshRate() != DisplayMode.REFRESH_RATE_UNKNOWN && m1.getRefreshRate() != m2.getRefreshRate())
        {
            return false;
        }
 
        return true;
    }
 
    //Make frame full screen
    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 = 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 hieght of window
    public int getHeight()
    {
        Window w = vc.getFullScreenWindow();
        if(w != null){
            return w.getHeight();
        }else{
            return 0;
        }
    }
 
    //Get out of full screen
    public void restoreScreen()
    {
        Window w = vc.getFullScreenWindow();
        if(w != null){
            w.dispose();
        }
        vc.setFullScreenWindow(null);
    }
 
    //Create image compatible with 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);
        }
        return null;
    }
}

---

bucky class:

Code :

---

import java.awt.*;
import javax.swing.JFrame;
import javax.swing.ImageIcon;
import javax.swing.*;
 
public class bucky2{
 
    public static void main(String args[]) {
        bucky2 b = new bucky2();
        b.run();
    }
 
    private Sprite sprite;
    private Animation a;
    private ScreenManager s;
    private Image bg;
    private static final DisplayMode modes1[] = {
        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),
    };
 
    //Load images and add scenes
    public void loadImages()
    {
        bg = new ImageIcon("C:\\temp\background1.jpg").getImage();
        Image face1 = new ImageIcon("C:\\temp\face1.png").getImage();
        Image face2 = new ImageIcon("C:\\temp\face2.png").getImage();
 
        a = new Animation();
        a.addScene(face1, 250);
        a.addScene(face2, 250);
 
        sprite = new Sprite(a);
        sprite.setVelocityX(0.3f);
        sprite.setVelocityY(0.3f);
    }
 
    //Main method called from main
    public void run()
    {
        s = new ScreenManager();
        try{
            DisplayMode dm = s.findFirstCompatibleMode(modes1);
            s.setFullScreen(dm);
            movieLoop();
        }finally{
            s.restoreScreen();
        }
    }
 
    //Play movie
    public void movieLoop()
    {
        long startingTime = System.currentTimeMillis();
        long cumTime = startingTime;
        while(cumTime - startingTime < 5000){
            long timePassed = System.currentTimeMillis() - cumTime;
            cumTime += timePassed;
            update(timePassed);
 
            //draw and update screen
            Graphics2D g = s.getGraphics();
            draw(g);
            g.dispose();
            s.update();
 
            try{
                Thread.sleep(200);
            }catch (Exception ex){}
        }
    }
 
    //Draws graphics
    public void draw(Graphics g)
    {
        g.drawImage(bg, 0,0, null);
        g.drawImage(sprite.getImage(), Math.round(sprite.getX()), Math.round(sprite.getY()), null);        
    }
 
    //Update sprite positioning
    public void update(long timePassed)
    {
        if(sprite.getX() < 0){
            sprite.setVelocityX(Math.abs(sprite.getVelocityX()));
        }else if(sprite.getX() + sprite.getWidth() >= s.getWidth()){
            sprite.setVelocityX(-Math.abs(sprite.getVelocityX()));
        }
 
        if(sprite.getY() < 0){
            sprite.setVelocityY(Math.abs(sprite.getVelocityY()));
        }else if(sprite.getY() + sprite.getHeight() >= s.getHeight()){
            sprite.setVelocityY(-Math.abs(sprite.getVelocityY()));
        }
 
        sprite.update(timePassed);
    }
}

---

When I run my code, in the bucky class on the update method :

Code :

---

public void update(long timePassed)
    {
        if(sprite.getX() < 0){

---

That is what gives me a null pointer exception. I have tried many things but I can't think of anything.
I have attached my code so if anybody wants to try it, I have done it in both blueJ and Eclipse.

Sorry about the long code!

Thank you.

Exception in thread "main" java.lang.NullPointerException
at bucky2.update(bucky2.java:87)
at bucky2.movieLoop(bucky2.java:63)
at bucky2.run(bucky2.java:49)
at bucky2.main(bucky2.java:10)


Screen goes black, but does nothing.

Problem is here: if(sprite.getX() < 0){

Quote:

---

Originally Posted by sim18

When I run my code, in the bucky class on the update method :

Code :

---

public void update(long timePassed)
    {
        if(sprite.getX() < 0){

---

That is what gives me a null pointer exception. I have tried many things but I can't think of anything.

---

In bucky2 class you have a field named sprite, right? Where sprite is declared, it is a reference variable that is automatically given a null value, right?

Well...

1. Where is the sprite reference variable given a value other than null? (What method creates a Sprite object named sprite?)
   
   
2. From where in the program is that method called?

Cheers!

Z

The method loadImages gives sprite a value of a.

Is my problem that loadImages in the bucky2 class is never called??

Quote:

---

Originally Posted by sim18

Is my problem...?

---

If that is the only place in the code where the sprite can be given a non-null value, and the NPE is generated because sprite has a null value when it is used, then I think you have found the reason for the NPE.

Cheers!

Z