Thread: Newbie Problem With Null Pointer Exception

Trying to build my first calculator from scratch and everything was going smooth but I am now getting hit with a handler coming up as a null pointer exception.

import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JButton;
import javax.swing.ImageIcon;
import javax.swing.Icon;
import javax.swing.JTextArea;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Scanner;
 
public class tuna extends JFrame {
	private JTextArea Screen;
	private JButton Num0;
	private JButton Num1;
	private JButton Num2;
	private JButton Num3;
	private JButton Num4;
	private JButton Num5;
	private JButton Num6;
	private JButton Num7;
	private JButton Num8;
	private JButton Num9;
	private ImageIcon INum0;
	private ImageIcon INum1;
	private ImageIcon INum2;
	private ImageIcon INum3;
	private ImageIcon INum4;
	private ImageIcon INum5;
	private ImageIcon INum6;
	private ImageIcon INum7;
	private ImageIcon INum8;
	private ImageIcon INum9;
	private int count =0;
	double Fnum;
	double Snum;
	boolean[] op = {false,false,false,false};  // not in use yet
	double Ans;
	// this is initializing all of the variables
 
	public tuna(){
		super("RaycasterJr's Calculator");
		setLayout(new FlowLayout());
		Fnum = 0;
		Snum = 0;
		Screen = new JTextArea(10,10);
		Screen.setEditable(false);
		add(Screen);
		JButton Nums[] = {Num0, Num1, Num2, Num3, Num4, Num5, Num6, Num7, Num8, Num9};
		Icon[] Numicons = new Icon[10];
		for(int count=0; count<=9;count++){ 
			Numicons[count] = new ImageIcon(getClass().getResource(count +"Num.png"));
			/// Setup the names of the images to co-ordinate with the count+"Num" system. This will allow for limited code.
		}
		for (int count = 0; count>=9; count++){
				Nums[count] = new JButton(Numicons[count]);
				add(Nums[count]);
				/// This will create all of the buttons with their own images
		}
 
 
		[COLOR="#FF0000"][COLOR="#FFFF00"]handlerNum H = new handlerNum();
		for (int count = 0; count<=9;count++){
			Nums[count].addActionListener(H);
			//This is where the error occurs
			//this is the error code below:
			//Exception in thread "main" java.lang.NullPointerException
				//at tuna.<init>(tuna.java:66)
				//at apples.main(apples.java:5)[/COLOR]
[/COLOR]
		}
	}
	public class handlerNum implements ActionListener{
		public void actionPerformed(ActionEvent Event){
			if (Event.getSource() == Num0){
				JOptionPane.showMessageDialog(null,"Testing"+Event.getSource());
			/// if a operator is click set that operators boolean to true and set the rest to false - this solves the multi-op problem
			}
		}
	}
}

Any help would be appreciated as I'm loving java and trying the gui from scratch but... hit a wall.
Again, thank you for any help.

Originally Posted by RaycasterJr

a null pointer exception

Always post the full text of the exception on the forum with your code and question.
Did you do a search on "Java null pointer exception"? Do you understand what that means? What trouble are you having in finding and fixing it?

Variables have to be declared and initialized.

Declared:

MyActionClass hListener; // variable names begin with lowercase letters, and single-letter names are lousy

Initialized:

hListener = new MyActionClass();

Declared and initialized:

MyActionClass hListener = new MyActionClass();

The array Nums (should be named "nums") must also have its elements initialized to something other than null or zero.

Thanks for the help - This concept allowed me to fix the problem with the arrays. Problem Solved - Mission Success!