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Thread: Runtime error-- Applet program

  1. #1
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    Default Runtime error-- Applet program

    Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at ModifiedStyleOptionsPanel$SayingListener.actionPer formed(ModifiedStyleOptionsPanel.java:70)
    at javax.swing.AbstractButton.fireActionPerformed(Abs tractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed (AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed (DefaultButtonModel.java:402)
    at javax.swing.JToggleButton$ToggleButtonModel.setPre ssed(JToggleButton.java:308)
    at javax.swing.plaf.basic.BasicButtonListener.mouseRe leased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.jav a:6505)
    at javax.swing.JComponent.processMouseEvent(JComponen t.java:3321)
    at java.awt.Component.processEvent(Component.java:627 0)
    at java.awt.Container.processEvent(Container.java:222 9)
    at java.awt.Component.dispatchEventImpl(Component.jav a:4861)
    at java.awt.Container.dispatchEventImpl(Container.jav a:2287)
    at java.awt.Component.dispatchEvent(Component.java:46 87)
    at java.awt.LightweightDispatcher.retargetMouseEvent( Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(C ontainer.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Conta iner.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.jav a:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719 )
    at java.awt.Component.dispatchEvent(Component.java:46 87)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.j ava:735)
    at java.awt.EventQueue.access$200(EventQueue.java:103 )
    at java.awt.EventQueue$3.run(EventQueue.java:694)
    at java.awt.EventQueue$3.run(EventQueue.java:692)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPri vilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPri vilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:708)
    at java.awt.EventQueue$4.run(EventQueue.java:706)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPri vilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java: 705)
    at java.awt.EventDispatchThread.pumpOneEventForFilter s(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(E ventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarch y(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThre ad.java:91)





    Program Written method is:




    //************************************************** ******************
    // StyleOptionsPanel.java Author: Lewis/Loftus
    //
    // Demonstrates the use of check boxes.
    //************************************************** ******************
    import javax.swing.*;
    import java.awt.*;
    import java.awt.event.*;
    import java.util.EventObject;




    public class ModifiedStyleOptionsPanel extends JPanel
    {
    private JLabel saying;
    private JCheckBox bold, italic;
    private JRadioButton rb1, rb2;
    //-----------------------------------------------------------------
    // Sets up a panel with a label and some check boxes that
    // control the style of the label's font.
    //-----------------------------------------------------------------
    public ModifiedStyleOptionsPanel()
    {
    saying = new JLabel ("Say it with style!");
    saying.setFont (new Font ("Helvetica", Font.PLAIN, 36));

    bold = new JCheckBox ("Bold");
    bold.setBackground (Color.cyan);
    italic = new JCheckBox ("Italic");
    italic.setBackground (Color.cyan);

    StyleListener listener = new StyleListener();
    bold.addItemListener (listener);
    italic.addItemListener (listener);

    JRadioButton rb1 = new JRadioButton("Set to red!");
    JRadioButton rb2 = new JRadioButton("Set to green!");
    rb1.setBackground (Color.cyan);
    rb2.setBackground (Color.cyan);

    ButtonGroup group = new ButtonGroup();
    group.add(rb1);
    group.add(rb2);

    SayingListener sm = new SayingListener();
    rb1.addActionListener (sm);
    rb2.addActionListener (sm);

    add(rb1);
    add(rb2);
    add (saying);
    add (bold);
    add (italic);
    setBackground (Color.cyan);
    setPreferredSize (new Dimension(300, 100));

    }

    private class SayingListener implements ActionListener
    {

    public void actionPerformed (ActionEvent e)
    {

    if ( rb1.isSelected()){
    saying.setForeground(Color.red);}
    else if (rb2.isSelected()){
    saying.setForeground(Color.yellow);}

    }
    }
    //************************************************** ***************
    // Represents the listener for both check boxes.
    //************************************************** ***************
    private class StyleListener implements ItemListener
    {
    //--------------------------------------------------------------
    // Updates the style of the label font style.
    //--------------------------------------------------------------
    public void itemStateChanged (ItemEvent event)
    {
    int style = Font.PLAIN;
    if (bold.isSelected())
    style = Font.BOLD;
    if (italic.isSelected())
    style += Font.ITALIC;
    saying.setFont (new Font ("Helvetica", style, 36));
    }
    }

    }







    Driver class is:




    //************************************************** ******************
    // StyleOptions.java Author: Lewis/Loftus
    //
    // Demonstrates the use of check boxes.
    //************************************************** ******************
    import javax.swing.JFrame;
    public class ModifiedStyleOptions
    {
    //-----------------------------------------------------------------
    // Creates and presents the program frame.
    //-----------------------------------------------------------------
    public static void main (String[] args)
    {
    JFrame frame = new JFrame ("Style Options");
    frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
    ModifiedStyleOptionsPanel panel = new ModifiedStyleOptionsPanel();


    frame.getContentPane().add (panel);
    frame.pack();
    frame.setVisible(true);
    }
    }

    --- Update ---

    Can any one help me out plz.....! whats wrong with my code ? it occurred in JGrasp editor.
    Comments will be appreciated


  2. #2
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    Default Re: Runtime error-- Applet program

    Welcome! Please read the Announcement topic at the top of the sub-forum and learn how to post your code in code or highlight tags plus other useful info for those new to the forum.

    As the error message indicates by "ModifiedStyleOptionsPanel.java:70," look on line 70 of the specified class and find which of the variables or objects on that line is null and either cause that variable to be something other than null or avoid using it when it is null.

  3. #3
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    Default Re: Runtime error-- Applet program

    Your problem is here:
    JRadioButton rb1 = new JRadioButton("Set to red!");
    JRadioButton rb2 = new JRadioButton("Set to green!");
    In your action performed method, you are using the class variables: rb1 and rb2. However, when you initialize them in your constructor, you are not initializing the variables in the scope of the action performed method, you are creating local variables which are only visible within your constructor.
    Since you did it correctly for your saying variable, this would appear to just be a typo. Remove the type before the variable names:
    rb1 = new JRadioButton("Set to red!");
    rb2 = new JRadioButton("Set to green!");
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