Not sure what my problem is.....

[ThrashingBoy]

Exception in thread "main" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(Unknown Source)
at PracticeSpace.Entity.<init>(Entity.java:24)
at PracticeSpace.Practice.main(Practice.java:8)

This is the problem I get, basically it has a problem with the picture being used. Here is a like the the tutorial I was following to right this code if you are interested, just with diff names for my classes.
The New Boston » Java Programming Tutorial – 63 – JButton Final Program
It is the second of a two parter.

I simply copy/pasted the name of the pngs I am using so I am sure the spelling is right and I have rechecked it many times because that is all I can think of. Help appreciated.

package PracticeSpace;

import javax.swing.JFrame;

public class Practice {
	public static void main(String[] args){
		
		Entity go = new Entity();
		go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		go.setSize(800,600);
		go.setVisible(true);
		
	}
}

package PracticeSpace;

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ImageIcon;
import javax.swing.Icon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
 
public class Entity extends JFrame {
	
	private JButton reg;
	private JButton custom;
	
	public Entity(){
		super("The title");
		setLayout(new FlowLayout());
		
		reg = new JButton("Regular button");
		add(reg);
		
		Icon b = new ImageIcon(getClass().getResource("40px-Japanese_Barn-icon.png"));
		Icon x = new ImageIcon(getClass().getResource("40px-Terra_globe_icon_light.png"));
		custom = new JButton("Custom", b);
		custom.setRolloverIcon(x);
		add(custom);
		
		HandlerClass handler = new HandlerClass();
		reg.addActionListener(handler);
		custom.addActionListener(handler);
	}
	
	private class HandlerClass implements ActionListener{
		public void actionPerformed(ActionEvent event){
			JOptionPane.showMessageDialog(null, String.format("%s", event.getActionCommand()));
		}
	}

}

[Junky]

On line 24 of your Entity class something is null. Chances are it cannot find your image files. One solution is to use absolute paths rather than relative ones.

[ThrashingBoy]

That did work. Thank you. But I just don't understand why it didn't work the way I had it though, especially when it worked for the guy making the video tutorial and several others. :(

For anyone who might view this thread this is all I changed in my code.

		Icon b = new ImageIcon("C:\\Users\\MyUser\\Desktop\\practice\\40px-Japanese_Barn-icon.png");
		Icon x = new ImageIcon("C:\\Users\\MyUser\\Desktop\\practice\\40px-Terra_globe_icon_light.png");