This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
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.
Joined: Dec 07, 2005
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?