Packaging question

[Gil Steidle]

I am attempting to understand java packaging and cannot get this to work. The java class is in c:\com\myapps and declared in the 1st line of code. What am I not doing correctly???

Thanks for the help!

package com.myapps;

class HelloWorld
{
	public static void main(String[] args)
	{
		System.out.println("Hello World Package");
	}
}

C:\com\myapps>javac HelloWorld.java

C:\com\myapps>java HelloWorld
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld (wrong nam
e: com/myapps/HelloWorld)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:14
1)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
Could not find the main class: HelloWorld. Program will exit.

C:\com\myapps>dir
Volume in drive C has no label.
Volume Serial Number is 4449-5A9A

Directory of C:\com\myapps

12/08/2010 09:32 AM <DIR> .
12/08/2010 09:32 AM <DIR> ..
12/08/2010 09:45 AM 444 HelloWorld.class
12/08/2010 09:32 AM 140 HelloWorld.java
2 File(s) 584 bytes
2 Dir(s) 58,300,485,632 bytes free

C:\com\myapps>

[Campbell Ritchie]

You ought to run it from outside the package structure with java com.myapps.HelloWorld. So you will have to navigate to the root folder first.
It might be better to have a "java" folder, rather than working on the root of "C".

[Gil Steidle]

Yes, moving to the root directory allowed the program to run without complaining. Thanks.

Where can I find a source for some further explanation about what's going on here? Specifically, why couldn't I run the program from the source directory? Isn't the package declaration giving the location of the class? And the class was there but java couldn't find it??? So confused.

[Campbell Ritchie]

Have you tried the Java™ Tutorials?

[Gil Steidle]

Ok, I have read the Java Tutorials on Packages and it helped a bit, but it did not help me with my question:

why couldn't I run the program from the source directory?

Also, if I follow your suggestion of:

It might be better to have a "java" folder, rather than working on the root of "C".

Would my directory structure then look like, c:\java\com\myapps?

Thanks!
Gil

[Campbell Ritchie]

Gil Steidle wrote:Ok, I have read the Java Tutorials on Packages and it helped a bit, but it did not help me . . .

Sorry. Anybody else know where you can find information? I couldn't find much in the Java™ Language specification.

. . . Would my directory structure then look like, c:\java\com\myapps? . . .

Yes.

And you're welcome