Flickering, graphical quality

Question

I am writing a Java program that has to do with moving a shae across the screen. The code is below.
There a Circle class which Extends the Shape class. The movingBallTest creates the circle and moves it across the screen repeatedly, shifting it down each time. (it leaves a trail as well)
The problem is that there is considerable flickering. I was hoping to increase the quality as well, maybe by using java2d or something. The code is very basic. Is there any other approach I can take to achieve the same goal? I have added the code below...Please tell me if and where I couldmake changes to improve it.
Please HELP!!!
D
import java.awt.*;
import java.awt.event.*;
class MovingBallTest {
private static Graphics g;
private static Circle c, c1;
private static DrawFrame df;
private static int wsize = 700, hsize = 705;
private static int x = 0, y = 0, x1 = x, y1 = y, delay = 2, delayNanos = 999, circleDia = 20, xSpace = 6, ySpace = 6, phase = 1;
private static int baseX = x, baseY = y;
public static void createWindow(){ //creates the window frame
df = new DrawFrame("Moving Ball");
df.show();
df.setSize(wsize, hsize);
g = df.getGraphicsContext();
public static void createShape(){ //creates instances of the ball(s)
c = new Circle(x, y, Color.blue, circleDia);
c1 = new Circle(x1, y1, Color.yellow, circleDia);
public static void resetX(){ //resets the x coordinate of the ball to the left corner of screen
c.setX(baseX);
c1.setX(baseX);
x = baseX;
public static void moveDownY(int downY){ //moves the y coordinate of the ball down by a given number
c.move(0, downY);
c1.move(0, downY);
public static void changeSpeed(int speed, int nanos){ //changes the time between each refresh
//You can make...maybe 5 speed settings
//Level l would have less delay etc.
delay = speed;
delayNanos = nanos;
public static void clearScreen(){ //clears the screen
g.setColor(Color.white);
g.fillRect(0, 0, wsize-1, hsize-1);
public static void moveLine(){ //moves the ball in a straight line across the screen (left to right)
while(x < wsize - circleDia){
//g.setColor(Color.white);
//g.fillRect(0, 0, size-1, size-1);
//clearScreen();
x = x + xSpace;
c.move(xSpace, 0);
c1.draw(g);
c.draw(g);
df.repaint();
c1.move(xSpace, 0);
try{
Thread.sleep(delay, delayNanos);
catch(InterruptedException e){}
catch(IllegalArgumentException e){}
public static void changeYspace(int newySpace){ //changes the spaces jumped as the ball goes down
ySpace = newySpace;
public static void main(String[] args){               
createWindow();
createShape();
for(int i = 0; i < 23; i++){
moveLine();
resetX();
clearScreen();
moveDownY(50);
import java.awt.*;
public abstract class Shape{
private int x;
private int y;
private Color color;
public Shape(int x, int y, Color color){
this.x = x;
this.y = y;
this.color = color;
public abstract void draw(Graphics g);
public abstract int getHeight();
public abstract int getWidth();
public Color getColor(){
return color;
public int getX(){
return x;
public int getY(){
return y;
public void setX(int x){
this.x = x;
public void setY(int y){
this.y = y;
public void move(int dx, int dy){
x += dx;
y += dy;
public void setColor(){
this.color = color;
import java.awt.*;
public class Circle extends Shape{
private int diameter;
//for a rectangle(for instance) you would need 2 variables
//one for width and the other for the height etc
public Circle(int x, int y, Color color, int diameter){
super(x, y, color);
this.diameter = diameter;
public void draw(Graphics g){
g.setColor(getColor());
g.fillOval(getX(), getY(), diameter, diameter);
public int getHeight(){
return diameter;
public int getWidth(){
return diameter;
}

Answer 1

You must use double buffering for drawing.
The old java.awt does not do this automatically, javax.swing does have easier support.
Look at the demos with the J2SDK, they are very impressive.