list<E>泛型的问题

@Transactional
public int addQuestions(Map<String, Object> map, List<Integer> njsIds) {

QuestionsNjs questionsNjs = new QuestionsNjs();
Questions q = new Questions();
try {
BeanUtils.copyProperties(q, map);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
questionsDao.insert(q);
int userId = q.getUserId();
int questionId = q.getId();
questionsNjs.setQuestionId(questionId);
questionsNjs.setStateForNjs(StateConstants.QuestionStateForNjs.PENDING.v());
for (Integer i : njsIds) {
questionsNjs.setNjsId(i);
//问题农技师关联表新增记录
questionsNjsDao.insert(questionsNjs);
//给每个农技师一条消息
addOneMessage(StateConstants.MessageType.QAMSG.v(),"tag",userId);
}
return 0;
}

这行报错for (Integer i : njsIds)  String不能转成Integer