Why won't it work? NullPointerException

[Mapisto]

Hi,

I've written this program which supposed to create a checkmate board.

Though when I've tried to run it, it'd stop on line 45 and write "Exception in thread "main" java.lang.NullPointerException"

What does it mean?

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.border.LineBorder;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.Dimension;


public class Checkmate {

	
	public static void main(String[] args) {
		new CheckMBoard();

	}

}

class CheckMBoard extends JFrame{
	
	private GridLayout grid= new GridLayout(8,8);
	private JPanel[][] checkers= new JPanel[8][8]; 
	private JLabel[][] nums= new JLabel[8][8]; 
	private LineBorder border= new LineBorder(Color.BLACK,2);
	Dimension size= new Dimension(5,5);
	
	
	public CheckMBoard (){
		setFrame();
		setCheckers();
		addComponents();
		
		
		
		
	}
	
	
	private void setCheckers(){
		for (int j=0; j<8; j++){
			if (j%2==0){
				for(int k=0; k<8; k++){
					if (k%2==0){
						checkers[j][k].setBackground(Color.BLUE);
						
					}
					else{
						checkers[j][k].setBackground(Color.YELLOW);
						
					}
					nums[j][k]= new JLabel(((j+1)*8+(k+1))+"",JLabel.CENTER);
					checkers[j][k].add(nums[j][k]);
					checkers[j][k].setBorder(border);
					checkers[j][k].setOpaque(true);
					checkers[j][k].setPreferredSize(size);
				}
				
			}
			else{
				for (int k=0; k<8; k++){
					if (k%2==0){
						checkers[j][k].setBackground(Color.YELLOW);
						
					}
					else{
						checkers[j][k].setBackground(Color.BLUE);
						
					}
					nums[j][k]= new JLabel(((j+1)*8+(k+1))+"",JLabel.CENTER);
					checkers[j][k].add(nums[j][k]);
					checkers[j][k].setBorder(border);
					checkers[j][k].setOpaque(true);
					checkers[j][k].setPreferredSize(size);
				}
			}
		}
		
		
		
		
		
		
		
		
	}
	
	private void setFrame(){
		//pack();
		setVisible(true);
		setAlwaysOnTop(isAlwaysOnTop());
		setResizable(false);
		setLocationRelativeTo(null);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setLayout(grid);
		
		
	}
	
	private void addComponents(){
		for (int j=0; j<8; j++){
			for(int k=0; k<8; k++){
				add(checkers[j][k]);
				
			}
			
			
		}
		
		
	
	}
	
	
	
	
	
	
}

Thanks!

[DarrylBurke]

1. When posting code to a forum, please remove unnecessary blank lines. Go through the Code Conventions for the Java Programming Language: Contents

2. Declaring an array does not automagically fill it. The elements of a newly declared array assume default values; zero for numeric primitives, false for boolean and null for object types.

db

[Mapisto]

Thanks!
I'll check it right away

[Mapisto]

Omg, I feel so stupid :|
This isn't the first time it happens to me.. I should have figured it on my own :(

Thanks again!