NullPointerException-Problem

Question

Why do I get a NullPointerException from this code?
The code should write �Test� in an applet.
import java.applet.*;
import java.awt.*;
public class fot extends Applet {     
     myCanvas bild;
     public void init(){
     setLayout(new BorderLayout());
     bild = new myCanvas();
     add("Center",bild);
public class myCanvas extends Canvas{
     Image buffer;
     Graphics gb;
     public void init(){               
     buffer = createImage(400, 300);
     gb = buffer.getGraphics();
     rita();
     public void rita(){
     gb.drawString("Test",50,50);
     repaint();
     public void paint(Graphics screen){
     screen.drawImage(buffer,0,0,this);

Answer 1

Ok, I changed the myCanvas class like this, but still the same error(nullPointerExseption)
public class myCanvas extends Canvas{
     Image buffer;
     Graphics gb;
     public myCanvas(){
     buffer = createImage(400, 300);
     gb = buffer.getGraphics();
     rita();     
     public void rita(){
     gb.drawString("Test",50,50);
     repaint();
     public void paint(Graphics screen){           
     screen.drawImage(buffer,0,0,this);
}