I do not have his book.*

No you don't - there is no such error message**.
Please copy/paste compile and runtime errors.
<http://www.physci.org/codes/javafaq.html#exact>

** I recognise what you are trying to say, but that
message has capitals.  The Java language is case
sensitive, and so am I.

* So I would need to see the *exact* code you are
using, in order to help further.

Note that a good group for people learning Java is
<http://www.physci.org/codes/javafaq.html#h>

A null pointer exception very probably means that you are trying to
dereference a null reference.  You have created a reference to an
object, but you have not actually created the object the reference is
meant to refer to.

 MyObject myob;

At this point you have a null reference - myob.  It is null because
you have not yet built the actual object for it to refer to.

 myob = new MyObject();

This line creates the object ("new") so your myob reference can now
refer to something.

Look at you code in your debugger.  Find the line where the error is
thrown.  Check every variable that is used nearby to see which one is
null - that is probably the cause of your problem.

rossum