Question

I am trying to assign text to buttons inside a loop but I am getting an NullPointerException.
I have initialized the button array inside constructor of the class and after initilizatoin, I call the following method. Here is the code where I am getting error.

public class Alfred
{
   private String names[]={"nfs","gta","maxpayne","hitman"};
   private JButton but[];

   public Alfred()
   {
    ...
     but= new JButton[4];
    AssignLettersToButtons();
   }
    private void AssignLettersToButtons()
    {       
        for(int i=0;i<names.length;i++)
        {
            but[i].setText(names[i]); // error
            pane1.add(but[i]);
        }
    }
}
}

The length of button array and names array is same. What is the reason for this exception and how can I solve it?

Regards

Answer 1

 but= new JButton[4]; 

This only allocates space for four array elements; each element is initialized to null, the default value for a reference type like your JButton objects.

but[0], but[1], but[2], but[3] are all null.

You should initialize them like this:

but[0] = new JButton(); //or whatever.