遍历聚合对象中的元素——迭代器模式（四）

class ProductList extends AbstractObjectList {  
    public ProductList(List products) {  
        super(products);  
    }  
    public AbstractIterator createIterator() {  
        return new ProductIterator();  
    }  
    //商品迭代器：具体迭代器，内部类实现  
    private class ProductIterator implements AbstractIterator {  
        private int cursor1;  
        private int cursor2;  
            cursor2 = objects.size() -1;  
        }  
        public void next() {  
            if(cursor1 < objects.size()) {  
                cursor1++;  
            }  
        }  
        public boolean isLast() {  
            return (cursor1 == objects.size());  
        }  
        public void previous() {  
            }  
        }  
        public boolean isFirst() {  
            return (cursor2 == -1);  
        }  
        public Object getNextItem() {  
            return objects.get(cursor1);  
        }   
        public Object getPreviousItem() {  
            return objects.get(cursor2);  
        }