package vs non-pacakged classes : java.lang.NoClassDefFoundError:

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Steve - 24 Feb 2006 18:34 GMT

Hi;

It has been a while since I have done anything with stand alone java
classes from the command line. I have gotten that dreaded
java.lang.NoClassDefFoundError.

I made a simple HelloWorld class ( not part of a package ) in
C:\home\Projects\exp

I used these commands in a bat file to run it:

-----------------------------------------------------------------
@echo off

SET CLASSPATH=.
echo ClASSPATH = %CLASSPATH%
echo
echo Running java HelloWorld
echo
java -Xmx1024m HelloWorld
-------------------------------------------------------------------

It ran fine.

However, when I recompiled the class to have the package statement
"package helloworld" I got the NoClassDefFound error.

I tried putting a copy of the HelloWorld class and executing it from
either of these directories:
C:\home\Projects\exp
C:\home\Projects\exp\helloworld

I also modified my bat file to be like this
-----------------------------------------------------------
@echo off

SET CLASSPATH=.;C:\home\Projects\exp\helloworld
echo ClASSPATH = %CLASSPATH%
echo
echo Running java helloworld.HelloWorld
echo
java -Xmx1024m helloword.HelloWorld
------------------------------------------------------------------

I could not get the class to run.

Any ideas or help would be appreciated.

Thanks much in advance

Steve

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Rhino - 24 Feb 2006 21:39 GMT

> Hi;
>
[quoted text clipped - 27 lines]
> C:\home\Projects\exp
> C:\home\Projects\exp\helloworld

You need to recompile the HellowWorld class after you add the package
statement then try to execute the revised version from
C:\home\Projects\exp\helloworld. If you simply moved the version the class
that didn't have the package name in it to the helloworld directory, that is
not going to work.

> I also modified my bat file to be like this
> -----------------------------------------------------------
[quoted text clipped - 11 lines]
>
> Any ideas or help would be appreciated.

The last line from the (second) batch file is clearly not going to work if
you've copied it accurately: the package name in the batch file is
"helloword", not "helloworld".

Try making the changes I suggested first; then, if it still doesn't work,
post back and I'll see if I can help. I'm just going off the top of my head
but I think one or both suggestions will help you. If not, I'll concoct my
own example and document what works for you. I've bumped into this problem a
few times over the years and I've been meaning to document the right answers
for ages....

--
Rhino

Reply to this Message

Fred Kleinschmidt - 24 Feb 2006 22:25 GMT

> Hi;
>
[quoted text clipped - 38 lines]
> echo
> java -Xmx1024m helloword.HelloWorld

Assuming you mena helloworld.HelloWorld, there is no such thing in your
CLASSPATH.
If instead you use
SET CLASSPATH=.;C:\home\Projects\exp
then place HelloWorld.class in C:\home\Projects\exp\helloworld is should
work.

When you have a package name "x.y.z", and you run
java x.y.z.SomeClass

it searches for SomeClass.class in directories A\x\y\z, B\x\y\z, ... etc.,
where A, B, etc. are in the CLASSPATH

Signature

Fred L. Kleinschmidt
Boeing Associate Technical Fellow
Technical Architect, Software Reuse Project

Reply to this Message

Paul Hamaker - 25 Feb 2006 09:54 GMT

Another way to put it, is to say, that the classpath is a collection of
starting-points, dirs or jars, where each contains directory-branches
or paths corresponding to package-names. Copy rt.jar to something.zip
and look inside, then you'll notice paths like java.lang, java.awt etc.
each containing their respective classes.
---------------
Paul Hamaker, SEMM, teaching ICT since 1987
http://javalessons.com

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Steve - 05 Mar 2006 11:50 GMT

Thanks for the help guys.

It looks like my bad spelling has gotten me again :)

Steve

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package vs non-pacakged classes : java.lang.NoClassDefFoundError:

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