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Thread: help me out from null pointer exception!!!

  1. #1
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    Default help me out from null pointer exception!!!

     
    import java.awt.event.*;
    import java.awt.*;
     
    class ExceptionGui extends Frame implements ActionListener,WindowListener,TextListener
    { 
      int numerator,denominator,result;
      Button b;
      TextField tf1,tf2;
      Label l1,l2,l3;
     
     
     public ExceptionGui()
     { 
        setLayout(new FlowLayout());
        setSize(300,250);
        Button b=new Button("enter");
        Label l1=new Label("enter numerator");
        Label l2=new Label("enter denominator");
        Label l3=new Label();
        TextField tf1=new TextField(15);
        TextField tf2=new TextField(15);
        add(l1);add(tf1);
        add(l2);add(tf2);
        add(b);add(l3);
        b.addActionListener(this);
         tf1.addTextListener(this);
         tf2.addTextListener(this);    
        addWindowListener(this);
        setVisible(true);
     
     
     
      }
      public void textValueChanged(TextEvent te)
      {
        if(te.getSource()==tf1)
                                             //got an Exception over here  
         {
           String x=tf1.getText();
            numerator=Integer.parseInt(x);
          }
       else
         {
           String y=tf2.getText();
           denominator=Integer.parseInt(y);
          }
      }
     
      public void actionPerformed(ActionEvent ae)
      {   
     
        result=numerator/denominator;
        l3.setText(String.valueOf(result));
      }
     public void windowOpened(java.awt.event.WindowEvent we){}
     public void windowClosing(java.awt.event.WindowEvent we){ System.exit(0);
     }
     public void windowClosed(java.awt.event.WindowEvent we){}
     
     public void windowIconified(java.awt.event.WindowEvent we){}
     public void windowDeiconified(java.awt.event.WindowEvent we){}
     public void windowActivated(java.awt.event.WindowEvent we){}
     public void windowDeactivated(java.awt.event.WindowEvent we){}
    }
    class Exception
    {
      public static void main(String args[])
      {
       ExceptionGui ex=new ExceptionGui();
      }
    }


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: help me out from null pointer exception!!!

    You forgot to copy and paste here the full text of the error message.
    Look at the statement where the error happened, find what variable had the null value and then backtrack in the code to see why that variable did not have a valid value.

    Make sure the code does not shadow class variables with local variables.

    Please edit your post and wrap your code with code tags:
    [code=java]
    <YOUR CODE HERE>
    [/code]
    to get highlighting and preserve formatting.
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: help me out from null pointer exception!!!

    can u pls check it out now

  4. #4
    Senior Member PhHein's Avatar
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    Default Re: help me out from null pointer exception!!!

    Norm has already told you what's wrong. Reread his reply. And the words are you and please. We're not limited to 160 characters in here.

  5. #5
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    Default Re: help me out from null pointer exception!!!

    Quote Originally Posted by Norm View Post
    You forgot to copy and paste here the full text of the error message.
    Look at the statement where the error happened, find what variable had the null value and then backtrack in the code to see why that variable did not have a valid value.

    Make sure the code does not shadow class variables with local variables.

    Please edit your post and wrap your code with code tags:
    [code=java]
    <YOUR CODE HERE>
    [/code]
    to get highlighting and preserve formatting.
    @Norm i have wrapped it.Can u pls check whats wrong with the code!!
    i am unable to solve exception from past 1hr..... pls help me out

  6. #6
    Super Moderator Norm's Avatar
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    Default Re: help me out from null pointer exception!!!

    Copy the full text of the error message and paste it here. It has important info about the problem.

    Make sure there are not variable declarations in a method or constructor that are shadowing class variables.
    If you don't understand my answer, don't ignore it, ask a question.

  7. #7
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    Default Re: help me out from null pointer exception!!!

    here is the exception i get when i try to insert number(integer) into the text field(both tf1 and tf2)

    *************ERROR************************
    Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at ExceptionGui.textValueChanged(Exception.java:45)
    at java.awt.TextComponent.processTextEvent(TextCompon ent.java:703)
    at java.awt.TextComponent.processEvent(TextComponent. java:672)
    at java.awt.TextField.processEvent(TextField.java:588 )
    at java.awt.Component.dispatchEventImpl(Component.jav a:4860)
    at java.awt.Component.dispatchEvent(Component.java:46 86)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.j ava:707)
    at java.awt.EventQueue.access$000(EventQueue.java:101 )
    at java.awt.EventQueue$3.run(EventQueue.java:666)
    at java.awt.EventQueue$3.run(EventQueue.java:664)
    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:680)
    at java.awt.EventQueue$4.run(EventQueue.java:678)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPri vilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java: 677)
    at java.awt.EventDispatchThread.pumpOneEventForFilter s(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForFilter(E ventDispatchThread.java:128)
    at java.awt.EventDispatchThread.pumpEventsForHierarch y(EventDispatchThread.java:117)
    at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:113)
    at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:105)
    at java.awt.EventDispatchThread.run(EventDispatchThre ad.java:90)
    ************************************************** ***************************
    Attached Images Attached Images

  8. #8
    Super Moderator Norm's Avatar
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    Default Re: help me out from null pointer exception!!!

    Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at ExceptionGui.textValueChanged(Exception.java:45)
    There is a variable with a null value on line 45. Look at line 45 in the your source and see what variable is null. Then backtrack in the code to see why that variable does not have a valid value.
    If you can not tell which variable it is, add a println just before line 45 and print out the values of all the variables on that line.
    If you don't understand my answer, don't ignore it, ask a question.

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