Error message from within emacs-processing:

Code:

test.pde:-1:0:-1:0: The public type processing must be defined in its own file
 

I'm trying to understand what happens when a sketch is compiled, so I can do test sketches. So I deleted my entire processing directory, decompressed the processing 1.0.9 tarball, descended into it's fist level directory and created a test sketch:

Code:

size(400, 400);
background(192, 64, 0);
stroke(255);
line(150, 25, 270, 350); 

The error in the processing-mode buffer gives me:

Code:

-*- mode: compilation; default-directory: "~/play/processing-1.0.9/" -*-
Compilation started at Wed Dec 30 17:24:52

/home/mantis/opt/processing-1.0.9/java/bin/java -classpath "/home/mantis/opt/processing-1.0.9/java/lib/rt\
.jar:/home/mantis/opt/processing-1.0.9/java/lib/tools.jar:/home/mantis/opt/processing-1.0.9/lib/antlr.jar\
:/home/mantis/opt/processing-1.0.9/lib/core.jar:/home/mantis/opt/processing-1.0.9/lib/ecj.jar:/home/manti\
s/opt/processing-1.0.9/lib/jna.jar:/home/mantis/opt/processing-1.0.9/lib/pde.jar" processing.app.Commande\
r --sketch="/home/mantis/play/processing-1.0.9/" --output="/home/mantis/play/processing-1.0.9/output" --r\
un
test.pde:-1:0:-1:0: The public type processing must be defined in its own file

Compilation finished at Wed Dec 30 17:24:54 

Whats happening here?
How can I get past this error and start doing sketches?

Is there any documentation on how the processing application 'Commander' does it's thing ?