Null Pointer Exception when executing a Java software

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dtian.tyson@googlemail.com - 31 Jan 2008 20:40 GMT

Hi,

I am using a java software for my research. It was distributed as
class files. The software takes a text file and do some computation
then it outputs the results. For some text files, the software runs
normally. However, for 2 files, the software outputs
java.lang.NullPointerException. Both files are in the same format as
the others. I don't have the source code, so I can not see the
problem.

Does anyone knows what could be wrong with the code?

The software is a data mining tool called Keel: http://sci2s.ugr.es/keel/download.php

Many thanks,
David

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Patricia Shanahan - 31 Jan 2008 20:52 GMT

> Hi,
>
[quoted text clipped - 9 lines]
>
> The software is a data mining tool called Keel: http://sci2s.ugr.es/keel/download.php

Unfortunately, NullPointerException for Java programs is a bit like "The
patient has no pulse" for humans. Without access to the body, all that
can be said is that the program broke on those inputs.

According to the web page "If you want to get the source code of the
Prototype, you only have notify us sending a mail to the address of the
administrators of the website.". Why not do that?

Patricia

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rossum - 31 Jan 2008 22:20 GMT

>Hi,
>
[quoted text clipped - 12 lines]
>Many thanks,
>David

Pick one of the two files, chop it in half and see which half crashes
the program. Repeat until you have a small file that crashes the
program. Look at that small file and see if you can see anything.

Patricia's suggestion is also a good one.

rossum

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Roedy Green - 01 Feb 2008 00:32 GMT

> For some text files, the software runs
>normally. However, for 2 files, the software outputs
>java.lang.NullPointerException. Both files are in the same format as
>the others. I don't have the source code, so I can not see the
>problem.

Use a decompiler to get some source to study. See
http://mindprod.com/jgloss/decompiler.html

also see
http://mindprod.com/jgloss/runerrormessages.html#NULLPOINTEREXCEPTION

Signature

Roedy Green, Canadian Mind Products
The Java Glossary, http://mindprod.com

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dtian.tyson@googlemail.com - 01 Feb 2008 12:06 GMT

> On Thu, 31 Jan 2008 12:40:30 -0800 (PST), dtian.ty...@googlemail.com
> wrote, quoted or indirectly quoted someone who said :
[quoted text clipped - 11 lines]
> Roedy Green, Canadian Mind Products
> The Java Glossary,http://mindprod.com

Thank you very much for all the help!

David

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alberto_keel - 14 Mar 2008 00:31 GMT

Recently, the user got in touch with the KEEL developing team and we detected
and fixed the problem in the method employed in his experiment.

KEEL software is free to downloading and use, but the source code is not
directly visible. However, you may ask for the code of a particular algorithm.
Furthermore, KEEL may be released under a GPL license in the future.

If you are interested in this Data Mine software, please visit our Home Page
at www.keel.es

Regards,

Alberto Fernández.

>Hi,
>
[quoted text clipped - 12 lines]
>Many thanks,
>David

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Null Pointer Exception when executing a Java software

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