Urs, please have a look at
The Java Tutorial. You can find answers to basic questions there very quickly, at least quicker than waiting for people to answer your posts on the forums here.
For this particular problem, look at
Lesson: Packages. Also read the
JDK documentation, especially the documentation of the
Java application launcher.
Go to the directory that contains your example directory and type this:
java example.src.MyFirstApp
[ March 19, 2007: Message edited by: Jesper Young ]