Tree {
{{
   Integer sum_labelsDJ(TraversalGraph labelsOfInterest) throws Exception {
   Visitor[] visitors = new Visitor[1];

   SummingVisitorDJ s = SummingVisitorDJ.parse("0");
   visitors[0] = (Visitor) s;
//   DisplayVisitor d = new DisplayVisitor();
//   visitorVector.addElement(d);
   Integer result = (Integer) labelsOfInterest.traverse((Object) this, visitors);
       return result;     
   }
}}
}


SummingVisitorDJ {
{{
   public void start() { total=0; System.out.println("begin"); }
   public void before(Label o) { total += o.get_v(); 
     System.out.println("before Label"); }
   public Object getReturnValue() {return new Integer(total);}
}}
}