code: public static <T extends AVObject> T createWithoutData(Class<T> clazz, String objectId) throws AVException{
      try {
        T obj = clazz.newInstance();
        obj.setClassName(Transformer.getSubClassName(clazz));
        obj.setObjectId(objectId);
        return obj;
      } catch (Exception ex) {
        throw new AVException(ex);
      }
    }
docs: create a new instance with particular class and objectId.
  @param clazz     class info
  @param objectId  object id
  @param <T>
  @return
  @throws AVException