Java Null Pointer Exception on JLIST

Question

OK so I'm trying to output the current string from an array that was put into a list... However when I click on the list I get a NullPointerException... :\

Help? :)

import java.applet.Applet;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;


public class lisTry extends JApplet implements MouseListener {

public static String newline;
public static JList list;

    public void init() {

            DefaultListModel listModel = new DefaultListModel();
            listModel.addElement("Debbie Scott");
            listModel.addElement("Scott Hommel");
            listModel.addElement("Alan Sommerer");

            JList list = new JList(listModel);


        this.getContentPane().add(list);

        list.addMouseListener(this);

        String newline = "\n";

        list.setVisible(true);

    }

    public void mousePressed(MouseEvent e) { }

    public void mouseReleased(MouseEvent e) {
       int index = list.getSelectedIndex();
       System.out.println("You clicked on: " + index);
    }

    public void mouseEntered(MouseEvent e) { }

    public void mouseExited(MouseEvent e) { }

    public void mouseClicked(MouseEvent e) { }

    public void paint(Graphics g) {

    } 
}

Thank you.

Just a note: > is used for marking up blockquotes; to mark up code you indent your snippets by 4 spaces. (I've made this change for you.) — BoltClock
– BoltClock, Commented Jul 16, 2010 at 18:49

haffax · Accepted Answer · 2010-07-16 18:52:35Z

5

Change this line:

JList list = new JList(listModel);

into this line:

list = new JList(listModel);

You are creating a local variable list in your constructor and thus hide the list field of your class. So the field lisTry.list stays null, hence the NullPointerException.

answered Jul 16, 2010 at 18:52

haffax

6,0081 gold badge34 silver badges30 bronze badges

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

2 Comments

test Over a year ago

That returns the number in the array not name :\

haffax Over a year ago

Yes, because you call getSelectedIndex(), which returns the index. See Java API docs. When you want to see the list item text itself, call getSelectedValue() instead.

Collectives™ on Stack Overflow

Java Null Pointer Exception on JLIST

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related