code: public static Iterator<Object> getKeys(Object[] array)
      {
          if (array == null)
          {
              return null;
          }
          ArrayList<Object> keyList = new ArrayList<Object>();
          int i = array.length - 2;
          while (i >= 0)
          {
              keyList.add(array[i]);
              i = i - 2;
          }
          return keyList.iterator();
      }
docs: Returns an Iterator of keys in the array.