Exception in thread "main" java.lang.NullPointerException Java GUI

Question

I am learning the basics of GUI Java on eclipse however whenever I seem to compile this program I get the compiler error message of:

Exception in thread "main" java.lang.NullPointerException
    at javax.swing.ImageIcon.<init>(Unknown Source)
    at ClassTwo.<init>(ClassTwo.java:11)
    at ClassOne.main(ClassOne.java:6)

I looked for anything from the line the error originated from but I cant seem to find anything wrong with it:

private Icon[] pics = {new ImageIcon(getClass().getResource(filename[0])),new ImageIcon(getClass().getResource(filename[1]))};

Any input on my error would be greatly appreciated. And here is the full code if it will help:

//ClassOne.Java
import javax.swing.JFrame;

class ClassOne {
    public static void main(String[] args){

        ClassTwo go = new ClassTwo();
        go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        go.setSize(300,200);
        go.setVisible(true);
    }
}


//ClassTwo.Java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class ClassTwo extends JFrame {

    private JComboBox box;
    private JLabel picture;

    private static String[] filename = {"b.png", "x.png"};
    private Icon[] pics = {new ImageIcon(getClass().getResource(filename[0])),new ImageIcon(getClass().getResource(filename[1]))};

    public ClassTwo(){
        super("Title");
        setLayout(new FlowLayout());

        box = new JComboBox(filename);

        box.addItemListener(
                new ItemListener(){ //anonymous class that implements item listener 
                    public void itemStateChanged(ItemEvent event){
                        if(event.getStateChange()==ItemEvent.SELECTED) //what was selected
                            picture.setIcon(pics[box.getSelectedIndex()]);
                    }
                }
        );

        add(box);
        picture=new JLabel(pics[0]);
        add(picture);
    }
}

Try breaking it up. Define the member as uninitialized (private Icon[] pics;) then in the constructor do three different lines, first (pics = new Icon[2]), then (pics[0] = new ImageIcon(getClass().getResource(filename[0]))) This should help tell you where the problem is. You can even break up the getClass() and getResource() calls to different lines which might narrow down the issue — MikeHelland
– MikeHelland, Commented Jan 25, 2014 at 2:41

Ashish · Accepted Answer · 2014-01-25 08:05:59Z

2

Turns out that my two resource files x.png and b.png were in the project folder rather then the package folder. Sorry for wasting your time.

edited Jan 25, 2014 at 8:05

Ashish

1,9412 gold badges14 silver badges17 bronze badges

answered Jan 25, 2014 at 2:43

user3183586

1671 gold badge6 silver badges15 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Exception in thread "main" java.lang.NullPointerException Java GUI

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related