[Swarm-Support] NullPointerException due to LispAppArchiver?

[Min San T. Co]

Hi!

I am following Charles Staelin's java swarm tutorial while building my own
model.  So far my model works upto SimpleSwarmBug2 (SimpleSwarmSchool2 in
my case since I am modelling the educational system).  However, I get:

Exception in thread "main" java.lang.NullPointerException
        at StartSimpleSchool.main(StartSimpleSchool.java:35)

when I create my SimpleSwarmSchool3.  I am able to execute SimpleSwarmBug3
without problems.  But I have no idea why my SimpleSwarmSchool3 won't
work.

I am working in a linux environment.

It seems that when I have

 modelSwarm = new ModelSwarm(Globals.env.globalZone);

in my StartSimpleSchool.java, my program works perfectly.  But when I use:

modelSwarm =
        (ModelSwarm)Globals.env.lispAppArchiver.getWithZone$key(
                            Globals.env.globalZone, "modelSwarm");

and include a SimpleSchool.scm file, where I list down all the parameters
and values that I need to set in my ModelSwarm class, I get an exception.

I'll appreciate any replies and suggestions...

min