In order to be able to execute your UObject, you need a main class. You also need to 'start' your UObject. This is a typical UObject main:

import liburbi.main.*;

public class Main {

    /// load urbijava library (see explanations in next section)
    static {
        System.loadLibrary("urbijava");
    }

    public static void main(String argv[]) {
        try
        {
	    /// Start here all your UObjects (this is done
	    /// thanks to the UStart function)
	    /// Give as parameter the name of your UObject
	    /// + .class
            UObjectJava.UStart (SimpleUObject.class);

	    /// Call our main ('main' function in UObjectJava class)
            UObjectJava.main (argv);
        }
        catch (Exception e)
        {
            System.out.println (e);
        }
    }
}