gcj and kaffe

[Gerard Robin <jag.robin18@wanadoo.fr>]

Hello,
I compiled the file: HelloWorldApp.java

class HelloWorldApp {
    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}

gcj -C HelloWorldApp.java 

the compiler has generated the file: HelloWorldApp.class. 

Then, I ran, kaffe HelloWorldApp, and I got sometimes:

Internal error: caught an unexpected exception.
Please check your CLASSPATH and your installation.
java/lang/NullPointerException
Internal error: caught an unexpected exception.
Please check your CLASSPATH and your installation.
java/lang/NullPointerException

or sometimes:

Hello World!

Can someone help me to understand what is wrong ?

TIA

P.S.
I have found this example in "The java tutorial" at http://java.sun.com/

-- 
Gerard