Do you have a main  method or the Party constructor?

If you did it would look something like

class Party {
public static void  main(String[] args){
Party p = new Party();
p.buildInvite();
}

public Party(){
}

public void buildInvite(){}
}

Note that you don't actually need a constructor with no arguments, but I
find that it is good form to put them in until your brain positively
knows what is happening.

Also do you have the directory in question in the class  path, or failing
that "." in your classpath (. is the current directory).

TO run  java class, the main  function must be there.

Add following method to your class

public static void  main (Sting args[]) {
// code  to be executed when this class  runs
}

you have't declared the main  method...
The compiler will compile without any error, since compiler won't care about
the main method..
At runtime it will look for the main method which is not there...
So u need a main method which inturn it creates reference of the Party
class.

Thanks so much everyone for your answers. I'm just a newbie  here, so
I'm surprised and happy to see such a response.

Regarding the NoSuchMethodError message I was getting, it probably
was the fact that I had no main() argument in the code.

I wrote to O'Reilly and they admitted that that piece of code  did not
work. They wouldn't say why, tho.

I have a long way to go with Java, so I'm especially anxious to start
writing code. Hopefully soon!

Okay, I'm an extreme newbie  as well, but I think I know your problem. In
order to run  a java  application, you have to have one method named
"main":

public static void  main(String[] args){
//do something, such as invoke your method above
}

It is okay to have a class  without a main  method, but only if you don't
try to invode that class directly (that is, you import it into other
code.)