NullpointerException in JOptionPane

Question

****It throws NullPointerException in JOptionPane code as following.****

public static void main(String[]args){


    String[] options={"Do it again?", "Exit"};
    int response=0;
    int indexOfZip;
    do{
        try{

        String dataStr=JOptionPane.showInputDialog("Enter a zip code");


        if(dataStr!=null){
             while (k<i){
                 if (place[k].equals(dataStr)){

                 indexOfZip=k;
                     k++;
                 }

             }
             int data=Integer.parseInt(dataStr);
             response=JOptionPane.showOptionDialog(null,
                           "You asked me to search for zip code:"+dataStr+"The zip code "+dataStr+" belongs to"+place[k].getTown()+","+place[k].getState()+"Do you want me to search again?",
                           "results",

                           JOptionPane.YES_NO_OPTION,
                           JOptionPane.QUESTION_MESSAGE,
                           null,
                           options,options[0]);


             System.out.println("You asked me to search for zip code:"+dataStr);
             System.out.println("The zip code "+dataStr+" belongs to"+place[k].getTown()+","+place[k].getState());
             System.out.println("Do you want me to search again?");

        }


        }catch(NumberFormatException e){
        JOptionPane.showMessageDialog(null,"Bad Numeric String, try again.", "Input Error",JOptionPane.ERROR_MESSAGE);

         }
    }while(response==0);
    if (response!=0){
       System.out.print("No");
       System.out.println("Good Bye!");
    }



    }

The terminal says the exception is for this line response=JOptionPane.showOptionDialog(null,

But I cannot see anything wrong here, because the "response" is initialized before.

Answer 1

It looks like place[k] must be null, and place[k].getTown() triggers NullPointerException. Watch the value of place[k] in a debugger (or add a print statement).