方法三： 删除ArrayList中重复元素，保持顺序

public static void removeDuplicateWithOrder(List list) {

   Set set = new HashSet();

   List newList = new ArrayList();

   for (Iterator iter = list.iterator(); iter.hasNext();) {

          Object element = iter.next();

          if (set.add(element))

             newList.add(element);

       }

      list.clear();

      list.addAll(newList);

     System.out.println( " remove duplicate " + list);

}