Problem in assigning randomed buttons

Hello There!!
I'm just a beginner so i would need your help with the

Code:

---

JButton x []= new JButton [12];
        int [] arr=new int[15];
       
    public Bahay_Kubling() {
            setLayout(new GridLayout(3,4));
            int randomNumbers = 12;
            Container con=getContentPane();
                ArrayList<Integer> numbers = new ArrayList<Integer>();
                int number = (int)(Math.random() * randomNumbers);
                numbers.add(number);
                for(int i = 0; i < randomNumbers-1; i++){
                        do{
                                number = (int)(Math.random() * 12);
                               
                        }while(numbers.indexOf(number)!=-1);
                        numbers.add(number);
                }
                for(Integer i: numbers){
                        System.out.println(i);
                        con.add(x[i]);
                        x[i].addActionListener(this);
                }
                       
               
            setTitle("Bahay Kubling Matching Game");
            setSize(300,400);
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            setLocationRelativeTo(null);
            setVisible(true);

---

I think I'm done with randoming unique numbers but the problem is assigning it to the buttons. I'm having error during runtime supposedly.. These is the error:

Code:

---

11
Exception in thread "main" java.lang.NullPointerException
    at java.awt.Container.addImpl(Container.java:1086)
    at java.awt.Container.add(Container.java:410)
    at Bahay_Kubling.<init>(Bahay_Kubling.java:35)
    at Bahay_Kubling.main(Bahay_Kubling.java:54)

---

Thanks in advance.. Hope you can help me. :(happy):

I did not see where you initialize JButtons.

Quote:

---

11
Exception in thread "main" java.lang.NullPointerException
at java.awt.Container.addImpl(Container.java:1086)
at java.awt.Container.add(Container.java:410)
at Bahay_Kubling.<init>(Bahay_Kubling.java:35)

---

At line 35 you call the add method with a null value. Check that line in your code to see what the problem is.

Quote:

---

Originally Posted by mine0926

I did not see where you initialize JButtons.

---

Sorry for late reply..
It's here:

Code:

---

public class Bahay_Kubling extends JFrame implements ActionListener{
        JButton x []= new JButton [12];
        int [] arr=new int[15];

---

:(nod):

Code:

---

JButton x []= new JButton [12];

---

That creates an array with 12 empty slots. It does not put any objects in the slots.
You need to assign them all with valid objects.

Quote:

---

Originally Posted by Norm

At line 35 you call the add method with a null value. Check that line in your code to see what the problem is.

---

Thanks for the reply..
Line 35 is :

Quote:

---

con.add(x[i]);

---

I don't know whats wrong.. please help.

What is the value of x[i]? Is it null?
See post#5

Quote:

---

Originally Posted by Norm

What is the value of x[i]? Is it null?
See post#5

---

Ok. I got it.! Thanks Mod..
I just added

Code:

---

x[i] = new JButton("1", new ImageIcon ("stan.jpg"));

---

before adding it to container..
Thanks a lot.

That should work better.