List<User> szUserList = new ArrayList<>();
 for (User user : userList) {
   if (user.getAddress().equals("shenzhen")) {
    szUserList.add(user);
   }
 }

 for (int i = 0; i < list.size() - 1; i++) {
            for (int j = list.size() - 1; j > i; j--) {
                if (list.get(j).equals(list.get(i))) {
                    list.remove(j);
                }
            }
        }

Set set = new HashSet();
        List<String> 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);
      
  }