Problem in assigning randomed buttons

[thesonyuh]

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

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:

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.

[mine0926]

I did not see where you initialize JButtons.

[Norm]

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.

[thesonyuh]

I did not see where you initialize JButtons.

Sorry for late reply..
It's here:

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

[Norm]

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.

[thesonyuh]

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 :

con.add(x[i]);

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

[Norm]

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

[thesonyuh]

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

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

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

before adding it to container..
Thanks a lot.

[Norm]

That should work better.