Thread: mainBall object wont update

ive created an object called mainBall which is just a little black ball that wont change position on the screen. the coordinates of the ball change but the actual ball itself wont change position and i have no idea why

import java.applet.Applet;
import java.awt.Color;
import java.awt.Component;
import java.awt.Event;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Rectangle;
import java.util.ArrayList;
import java.util.concurrent.TimeUnit;
 
public class game extends Applet implements Runnable
{
    static final int WIDTH = 450;
    static final int HEIGHT =  450;
    private Image dbImage;
    private Graphics dbg;
 
    public static long NEW_DOT_FREQ = TimeUnit.SECONDS.toMillis(3);
    public long lastUpdateTime;
    public long timeSinceLastNewDot;
 
 
    public ArrayList<Ball> BALLS;
 
    Color[] color = {Color.red, Color.blue, Color.green, Color.yellow, Color.magenta, Color.black};
    int colorIndex;
 
    static final int NUM_OF_BALLS = 4;  
 
    int i;
    int t;
 
    MainBall mainBall = new MainBall(100, 100, 10, 10, 100, 100, 0, 0);
 
    Thread updateTime = new updateTime();
 
    public void start()
    {
    	lastUpdateTime = System.currentTimeMillis();
 
        Thread th = new Thread(this);
        th.start();//start main game  
 
        updateTime.start();
    }
 
    public void updateGame()
    {
        //Get the current time
        long currentTime = System.currentTimeMillis();
        //Calculate how much time has passed since the last update
        long elapsedTime = currentTime - lastUpdateTime;
        //Store this as the most recent update time
        lastUpdateTime = currentTime;
 
        //Create a new dot if enough time has passed
        //Update the time since last new dot was drawn
        timeSinceLastNewDot += elapsedTime;
 
        if (timeSinceLastNewDot >= NEW_DOT_FREQ)
        {
            int newX = randomNumber();
            int newY = randomNumber();
 
            debugPrint("New dot created at x:" + newX + ", y:" + newY + ".");
 
            BALLS.add(new Ball(newX, newY, 20, 20));
 
            timeSinceLastNewDot = 0;
        }
    }
 
    private void debugPrint(String value)
    {
        System.out.println(value);
    }
 
    public class updateTime extends Thread implements Runnable
    {
        public void run()
        {
            for(t = 0; ; t++)
            {
                try
                {
                    Thread.sleep(1000);
                }
                catch(InterruptedException e){}
            }
        }
    }
 
    public int randomNumber()
    {
        return (int)(Math.random() * 400);
    }
 
    public int getRandomColor()
    {
    	return (int)(Math.random() * 6);
    }
 
    public class MainBall
    {
    	int x;
    	int y;
    	int width;
    	int height;
        int xpos;
        int ypos;
        int xspeed;
        int yspeed;
 
    	public MainBall(int x, int y, int width, int height, int xpos, int ypos, int xspeed, int yspeed)
    		{
    	        this.x = 100;
    	        this.y = 100;
    	        this.width = 10;
    	        this.height = 10;
    	        this.xpos = 100;
    	        this.ypos = 100;
    	        this.xspeed = 0;
    	        this.yspeed = 0;
    	    }
 
    	public void paintMainBall(Graphics g)
    	{
    		g.setColor(Color.black);
    		g.fillOval(x, y, width, height);
    	    g.drawString(xpos + ", " + ypos, 20, 40);      
    	}	
    }//mainBall
 
    class Ball
    {
        int x;
        int y;
        int width;
        int height;    
 
        public Ball(int x, int y, int width, int height)
        {        
             this.x = x;
             this.y = y;
             this.width = width;
             this.height = height;
        }//end ball
 
        public void paint(Graphics g)
        {
                g.setColor(color[getRandomColor()]);
                g.fillOval(x, y, width, height);
        }                    //end paint
 
 
    }                    //ball class
 
    public void update(Graphics g)                    //double buffer don't touch!!
    {
        if(dbImage == null)
        {
            dbImage = createImage(this.getSize().width, this.getSize().height);
            dbg = dbImage.getGraphics();
        }
 
        dbg.setColor(getBackground());
        dbg.fillRect(0, 0, this.getSize().width, this.getSize().height);
 
        dbg.setColor(getForeground());
        paint(dbg);
 
        g.drawImage(dbImage, 0, 0, this);
    }
 
    public boolean keyDown (Event e, int key)
    {
        if(key == Event.LEFT)
        {
            mainBall.xspeed = -5;
            mainBall.yspeed = 0;
        }
 
        if(key == Event.RIGHT)
        {
            mainBall.xspeed = 5;
            mainBall.yspeed = 0;
        }
 
        if(key == Event.UP)
        {
            mainBall.yspeed = -5;
            mainBall.xspeed = 0;
        }
 
        if(key == Event.DOWN)
        {
            mainBall.yspeed = 5;
            mainBall.xspeed = 0;
        }
        return true;
    }
 
    public void run()
    {
        while(true)
        {
            repaint();
 
            if (mainBall.xpos < 1)
            {
                mainBall.xpos = 449;
            }
 
            if (mainBall.xpos > 449)
            {
                mainBall.xpos = 1;
            }
            if (mainBall.ypos < 1)
            {
                mainBall.ypos = 449;
            }
 
            if (mainBall.ypos > 449)
            {
                mainBall.ypos = 1;
            }
            mainBall.ypos += mainBall.yspeed;
            mainBall.xpos += mainBall.xspeed;
            try
            {
                Thread.sleep(20);
            }
            catch(InterruptedException ex){}
        }
      } 
 
    public void init()
    {        
        this.setSize(WIDTH, HEIGHT);
 
        BALLS = new ArrayList<Ball>();
    }
 
    public void paint(Graphics g)
    {    
 
        g.drawString("time: " + t, 20, 20);
 
        mainBall.paintMainBall(g);
 
        for (Ball ball : BALLS)
        {
            ball.paint(g);
        }
 
        updateGame();
    }
 
 
}

the actual ball itself wont change position

Where does the code change the location of the ball?

The paintmainball method does not change the values of any variables. What variables control the balls location? Where are those variables changed?

Define a Rectangle object at the x,y location and size you want it to be using a new statement, assign it to a variable and return the variable (or return what was created by the new statement directly).