AS400 Toolbox for Java

This is a question about JavaAppliactionCall class in AS400 Toolbox for Java.

I use VJavaApplicationCall to call a java program on AS400 by using the following code:

AS400 system = new AS400("myAS400");
JavaApplicationCall javaCall = new JavaApplicationCall(system);
VJavaApplicationCall vJavaCall = new VJavaApplicationCall(javaCall);
JFrame f = new JFrame ("JavaApplicationCallExample");
f.getContentPane().setLayout(new BorderLayout ());
f.getContentPane().add("Center", vJavaCall);
f.pack();
f.show();
On the displayed GUI commend line, how should I know I am at the current AS/400 directory to run my Test.class? If I just run it as:

java Test
I got java.lang.NoClassDefFoundError.  The same jave program has no problem running on AS/400 QShell. 
Do I need to chang the directory to where my class reside?  How to do it?

Thanks for your help.