Error NullPointerException in my program

[Linux-Us]

Hi
Do not know what is wrong with the code it is given a java.lang.NullPointerException error when running it. Can any one help because I have no clue what is going wrong with this code. Thanks in advance. I have posted my code below.

private sqr background;

 public sqr getbg()
   {
      return background;
   }

  public void movebg()    /** this is what method i am trying to run */
     {
        background.setXPos(75);
      }

This is the sqr class

public void setXPos(int x)
   {
      this.xPos = x;
      this.update();
   }

[Modifier]

Hello,
I think there is a problem in object background. It is not properly instantiated. Think that it the object the compiler is referring to. To make the constructor instantiate the object background. Just try this part of code.

public <Class Name> () {
           
         background  = new Square();
 }

If any problem do post back.

[Linux-Us]

Hi
Thanks for the reply and for the code part.

public <Class Name> () {
           
         background  = new Square();
 }

I have tried it but not sure what you are trying to say in the code. Any more explanation will be appreciated. Here I use this part of code to get a dice with one spot.

Square s = new Square();
Circle c1 = new Circle();
Circle c2 = new Circle();
Circle c3 = new Circle();
Circle c4 = new Circle();
Circle c5 = new Circle();
Circle c6 = new Circle();
Circle c7 = new Circle();
Dice di = new Dice(s, c1, c2, c3, c4, c5, c6, c7);

Any explanation. Thanks again.

[Modifier]

Hi

Square s = new Square();
Circle c1 = new Circle();
Circle c2 = new Circle();
Circle c3 = new Circle();
Circle c4 = new Circle();
Circle c5 = new Circle();
Circle c6 = new Circle();
Circle c7 = new Circle();
Dice di = new Dice(s, c1, c2, c3, c4, c5, c6, c7);

I observed what you have posted in the code. The mistake you have done is that you have not created the background variable. Just take a look at the constructor of the class Dice. If I am not wrong then there should be something like this

background = bg;

or even you can use this

background = new Square();