Results 1 to 3 of 3
Thread: java.lang.NullPointerException
- 02-07-2008, 02:40 AM #1
Member
- Join Date
- Feb 2008
- Posts
- 7
- Rep Power
- 0
java.lang.NullPointerException
I am working on a gui application that rolls 5 dice. I have my own separate die and dice classes. I am having trouble making the GUI though. I keep getting a NullPointer.
App.java:
AppPanel.java:Java Code:import javax.swing.JFrame; public class App { public App() { // TODO Auto-generated constructor stub } public static void main(String[] args) { JFrame frame = new JFrame ("Push Counter"); frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE); frame.getContentPane().add(new AppPanel()); frame.pack(); frame.setVisible(true); } }
Someone else in the class was having the same problem as me, but theres was due to never initializing their buttons and labels. Mine are initialized so I cant figure out why I am getting this error. Can anyone help me out?Java Code:import java.awt.*; import java.awt.event.*; import javax.swing.*; public class AppPanel extends JPanel { private Die die1, die2, die3, die4, die5 = new Die(6); private Dice dice = new Dice(); private JLabel total, d1, d2, d3, d4, d5 = new JLabel("0"); private JButton rollAll, roll1, roll2, roll3, roll4, roll5 = new JButton("Roll"); public AppPanel() { dice.addDie(die1); dice.addDie(die2); dice.addDie(die3); dice.addDie(die4); dice.addDie(die5); //rollAll.addActionListener(new RollAllListener()); add(rollAll); add(total); add(roll1); add(d1); add(roll2); add(d2); add(roll3); add(d3); add(roll4); add(d4); add(roll5); add(d5); } public static void main(String[] args) { // TODO Auto-generated method stub } private class RollAllListener implements ActionListener { public void actionPerformed (ActionEvent event) { dice.rollAll(); } } }
- 02-07-2008, 05:48 AM #2
To test/find_out you can try something like:Java Code:// die1, die2, die3, die4 are declared and not instantiated // and so are null. // die5 = new Die(6) — is not null private Die die1, die2, die3, die4, die5 = new Die(6); private Dice dice = new Dice(); // total, d1, d2, d3, d4 are all null, not assigned any value. // d5 = new JLabel("0") — okay, instantiated. private JLabel total, d1, d2, d3, d4, d5 = new JLabel("0"); // rollAll, roll1, roll2, roll3, roll4 are all null. // roll5 = new JButton("Roll") is okay. private JButton rollAll, roll1, roll2, roll3, roll4, roll5 = new JButton("Roll");
Java Code:public AppPanel() { System.out.println("die1 = " + die1); dice.addDie(die1);
- 02-08-2008, 09:01 AM #3
Member
- Join Date
- Feb 2008
- Posts
- 7
- Rep Power
- 0
Similar Threads
-
java.lang.NullPointerException
By ravian in forum New To JavaReplies: 1Last Post: 01-13-2008, 07:39 PM -
ArrayList: Exception in thread "main" java.lang.NullPointerException
By susan in forum New To JavaReplies: 1Last Post: 07-16-2007, 06:32 AM -
AWT-EventQueue-0 java.lang.NullPointerException
By susan in forum NetBeansReplies: 2Last Post: 07-16-2007, 06:21 AM -
java.lang.NullPointerException
By Felissa in forum Advanced JavaReplies: 1Last Post: 07-05-2007, 06:02 AM -
Error Java.lang.NullPointerException in JBuilder2006
By Jack in forum Other IDEsReplies: 2Last Post: 07-02-2007, 02:29 AM


LinkBack URL
About LinkBacks
Reply With Quote
Bookmarks