[Java] Exception in thread "main" java.lang...

[Sascha Balkau]

Hi list,
I already have a question too ...

When I try to run a compiled Java class from the DOS prompt (Windows) I 
always get the following error:
Exception in thread "main" java.lang.NoClassDefFoundError: Foo/class

This doesn't happen if I build/run from the Eclipse IDE. Could somebody tell 
me what the problem is? I'm rather new to Java.

Sascha