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From Steve Loughran <ste...@apache.org>
Subject Re: Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
Date Tue, 17 May 2011 09:44:49 GMT
On 16/05/11 21:12, Lạc Trung wrote:
> I'm using Hadoop-0.21.
> ---
> hut.edu.vn

At the top, it's your code, so you get to fix it. The good thing about 
open source is you can go all the way in.

This is what I would do in the same situation
-Grab the 0.21 source JAR
-add it your IDE
-have a look at what line it's NPEing on
-work out what variable's being null would trigger that. Usually its 
whatever object has just had a method called on it.
-work out why that's null (usually some config/startup thing was missing).
-If its a repeatable problem, try adding some checks in advance, dump 
state to the console, etc.
-fix what is probably a setup problem

If it's some other problem (race condition etc), life is harder


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