Null Pointer Exception when executing a Java software

Discussion in 'Java' started by dtian.tyson@googlemail.com, Jan 31, 2008.

  1. Guest

    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
    , Jan 31, 2008
    #1
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  2. wrote:
    > 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


    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
    Patricia Shanahan, Jan 31, 2008
    #2
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  3. rossum Guest

    On Thu, 31 Jan 2008 12:40:30 -0800 (PST),
    wrote:

    >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

    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
    rossum, Jan 31, 2008
    #3
  4. Roedy Green Guest

    On Thu, 31 Jan 2008 12:40:30 -0800 (PST),
    wrote, quoted or indirectly quoted someone who said :

    > 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
    --
    Roedy Green, Canadian Mind Products
    The Java Glossary, http://mindprod.com
    Roedy Green, Feb 1, 2008
    #4
  5. Guest

    On 1 Feb, 00:32, Roedy Green <> wrote:
    > On Thu, 31 Jan 2008 12:40:30 -0800 (PST),
    > wrote, quoted or indirectly quoted someone who said :
    >
    > > 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.  Seehttp://mindprod.com/jgloss/decompiler.html
    >
    > also seehttp://mindprod.com/jgloss/runerrormessages.html#NULLPOINTEREXCEPTION
    > --
    > Roedy Green, Canadian Mind Products
    > The Java Glossary,http://mindprod.com


    Thank you very much for all the help!

    David
    , Feb 1, 2008
    #5
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