This interface is used to get the reply from a PhantomObject.callObject method
where the object might be of type REXX Application running in a separate thread.
The method "onObjectReply" is called when the object has completed execution.
Called when the object has completed execution. The reply is the String
that the object chose to return (regardless of object type).
The reply string might be null if there are parameter errors or if
there was a failure in executing the object.