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Not able to rectify the swing Exception

Sachin Dimble
Ranch Hand

Joined: Dec 07, 2005
Posts: 100
Hi Ranchers,
I am populating an JTable with some information. everything works fine but while populating table am getting following exception(still am able to populate table correctly)

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.basic.BasicTableHeaderUI.paintCell(BasicTableHeaderUI.java:394)

what could be the reason for this exception. and how to rectify the same?

thanks in advance!
Sachin!!!
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 39393
    
  28
Once you go into GUIs you get several threads; you may crash a Thread with an Exception and still have the display on screen.
NullPointerExceptions are a standard beginner's problem. The hardest part is finding what causes them. Get a full stack trace for your Exception and find the first line in your code where it occurs. Look through every object in that line; you have done one of the following things:
  • Declared it and forgotten to instantiate it,
  • set it to null,
  • or lost it and forgotten to re-instantiate it.
  • If you can't work out which it is, insert a test line one line before where it happens rather like this:-If you get a lot of incomprehensible writing on screen, assume your object exists; if it doesn't the word "null" will appear. Find where you were supposed to instantiate that object and do so.

    This exception appears very frequently; you will find lots more about it on these fora if you do a search.
    Sachin Dimble
    Ranch Hand

    Joined: Dec 07, 2005
    Posts: 100
    well it's resolved!!! i implemented the swing worker thread while populating the Jtable, now my application is migrated to -
    java version "1.6.0_01"
    Java(TM) SE Runtime Environment (build 1.6.0_01-b06)
    Java HotSpot(TM) Client VM (build 1.6.0_01-b06, mixed mode, sharing

    now when i click on coloumn of Jtable for sorting the rows am getting the same exception. since these exception is in api code itself i can't debug it by printing the objects which are going null.
    How shall i supress this exception?

    Thanks,
    Sachin.
     
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