Calling Javascript from Java using LiveConnect

I've been struggling with this all day. I want to call a JavaScript function from a java applet, using code that will work in IE4 and Nav 4. LiveConnect should do this. I've followed examples on netscape web site. The following java code below works on IE4 but not on Nav 4. Why?

import netscape.javascript.JSObject;
 
public class Example3 extends Applet {
   JSObject win;

      /**
       * Initialisation section.
       */
      public void init() {

        // Get a reference to the Navigator Window
        try{
            win = JSObject.getWindow(this);
        }
        catch (Exception e){
                   setBackground(Color.red);
        }        

            Button b = new Button("Say Hello");
            b.addActionListener(new ActionListener() {
                  public void actionPerformed(ActionEvent e) {
                        System.out.println("in button click");
                        sayHello();
                  }
            });
            this.add(b);
      }

   public void sayHello() {
        win.eval("alert(\"Hello World\");");
   }

      public void paint(Graphics g) {
            g.drawString("Click the button to say hello", 100, 100);
      }
}