public static void main(String [ ] args){
    TwoElement two1 = new TwoElement (3 , 3);
    TwoElement two2 = new TwoElement (2 , 7);
    ThreeElement three1 = new ThreeElement (3 , 4 , 5);
    List<NumberElement> numberElements = new ArrayList<NumberElement >();
    numberElements.add(two1);
    numberElements.add(two2);
    numberElements.add(three1);
    System.out.println (" Visiting element list with SumVisitor");
    NumberVisitor sumVisitor = new SumVisitor ();
    sumVisitor.visit(numberElements);
    System.out.println ("\nVisiting element list with TotalSumVisitor");
    TotalSumVisitor totalSumVisitor = new TotalSumVisitor ();
    totalSumVisitor.visit(numberElements);
    System.out.println ("Total sum: " + totalSumVisitor.getTotalSum ());
    }