Quick Homework Question (Moving a ball)

Question

I took a course in C and now im into java. I never created any graphics in C. I need to finish a java applet that makes a red ball appear in the center of a blue background and then move down and up the screen.
Any information of how to make it move would help...
This is what I have so far:
//This applet draws an animated bouncing ball with uniform speed.
//The ball starts at the center of the graphics page and bounces off
//the top and bottom
import java.awt.*;
import java.applet.Applet;
public class BouncingBall extends Applet {
    //Dimensions of Applet:
    public final int width = 500;
    public final int height = 500;
    //Size and speed of ball:
    public final int diameter = 20;
    public final int speed = 5;
    //Milliseconds to pause between frames:
    public final int pause = 20;
    public void paint (Graphics page) {
        setBackground(Color.blue);
        page.fillOval(250 - diameter/2, 250 + diameter/2, diameter, diameter);
        page.setColor(Color.red);
        //Loop forever;
        while (true) {
            //if (x_pos > 500- diamter/2)
            //Pause between frames:
            try { Thread.sleep(pause) ; } catch (Exception e) { };
//End-of-FileThanks

Answer 1

I just can't get the ball to move now. Can anyone find what I am doing wrong?
//This applet draws an animated bouncing ball with uniform speed.
//The ball starts at the center of the graphics page and bounces off
//the top and bottom
//Known Problems:
// - None
import java.awt.*;
import java.applet.Applet;
public class BouncingBall extends Applet {
    //Dimensions of Applet:
    public final int width = 500;
    public final int height = 500;
    //Size and speed of ball:
    public final int diameter = 20;
    public final int speed = 5;
    //Milliseconds to pause between frames:
    public final int pause = 20;
    int y = 250;
    public void paint (Graphics page) {
        page.setColor(Color.blue);
        page.fillRect(0,0,500,500);
        page.setColor(Color.red);
        page.fillOval(250 - 10, y - 10, 20, 20);
        //Loop forever;
    public void run()
        while (true) {
            if (y<=450){
                y--;
                repaint();
                return;
            else if (y>=10){
                y++;
                repaint();
                return;
            //Pause between frames:
            try { Thread.sleep(pause) ; } catch (Exception e) { };
}Thanks again