Thread: Java bouncing balls flickering

Hi all, I am very new to Java and need help with this code if possible. I am to create an applet that creates a number of balls derived from a HTML.They bounce of the bounds of the frame but do not bounce of each other!

I think I have most of the code however this keeps Flickering any help appreciated! I am very new to Java and coding in general, threads are killing me!
I have been at this for days so any help at all appreciated!

import java.applet.*;
import java.awt.*;
import java.util.Random;
 
class Ball {
 
    Graphics g;
    int x;
    int y;
    int xmove; // x movement
    int ymove; // y movement
    int radius;
    Color bColor;
 
    private final Random generator = new Random();
 
    public Ball(Color c,int width,int height) {
 
        x = generator.nextInt(width);
        y = generator.nextInt(height);
        // calculate random direction (and speed)
        xmove = generator.nextInt(5) + 1;
        ymove = generator.nextInt(5) + 1;
        radius = 10;
        bColor = c;
    }// end constructor Ball
 
    public void paint(Graphics graphik) {
 
        graphik.setColor(bColor);
        graphik.fillOval(x - radius, y - radius, 2 * radius, 2 * radius);
 
 
    }// end method paint
 
    public void moveBall(int width,int height) {
        if ((x - radius + xmove < 0) || (x + radius + xmove > width)) {
            xmove = -xmove;
        }
        if ((y - radius + ymove < 0) || (y + radius + ymove > height)) {
            ymove = -ymove;
        }
        // recalulate the x,y coordinates of the circle
        x += xmove;
        y += ymove;
    }// end method moveBall
}// end class ball
 
public class BallsBounce extends Applet implements Runnable {
 
    Thread th;
    int numBalls;
    Graphics graphic;
    Image img;
    Ball balls[];
    private Color Colors[] = {Color.GRAY, Color.BLUE, Color.ORANGE, Color.CYAN, Color.BLACK, Color.MAGENTA, Color.GREEN, Color.PINK, Color.YELLOW, Color.RED};
    int c = 0; // count the colors used
 
    public void init() {
        setBackground(Color.LIGHT_GRAY);
        numBalls = Integer.parseInt(getParameter("balls"));
        //
        img = createImage(getWidth(), getHeight());
        graphic = img.getGraphics();
 
        balls = new Ball[numBalls];
 
 
        for (int i = 0; i < numBalls; i++) {
            if (c >= 10) {
                c = 0;
            }// end if
 
            balls[i] = new Ball(Colors[c],getWidth(), getHeight());
            c++;
        }// end for
    }// end method init
 
    public void start() {
        if (th == null) {
            th = new Thread(this);
            th.start();
        }// end if
    }// end method start
 
    public void run() {
        while (true) {
 
            for (int j = 0; j < numBalls; j++) {
                balls[j].moveBall(getWidth(), getHeight());
 
            }// end for
 
            try {
                th.sleep(20);
            }// end try
            catch (InterruptedException except) {
            }// end catch
            repaint();
        }// end while
    }// end method run
 
    public void paint(Graphics g) {
        super.paint(g);
        //g.clearRect(0, 0, this.getWidth(), this.getHeight());
        graphic.clearRect(0, 0, this.getWidth(), this.getHeight());
        for (int k = 0; k < numBalls; k++) {
 
            balls[k].paint(graphic);
            g.drawImage(img, 10, 10, this);
        }// end for
 
 
    }// end method paint
}// end class BallsBounce