帮我注释下代码Override public List getQuestionsByBankIdInteger bankId String username 协同过滤 获取历史考试中错题 User user = userServicegetUserByUsernameusername; QueryWrapperExamRecord wrapper = new QueryWr

// 通过传入的题库id和用户名获取题目列表，使用协同过滤的方法 @Override public List getQuestionsByBankId(Integer bankId, String username) {

// 获取该用户的历史考试记录
User user = userService.getUserByUsername(username);
QueryWrapper<ExamRecord> wrapper = new QueryWrapper<>();
wrapper.eq("user_id", user.getId());
List<ExamRecord> examRecords = examRecordMapper.selectList(wrapper);

// 根据历史考试记录中的错题记录查询错题列表
List<Integer> quesIds = new ArrayList<>();
for (ExamRecord examRecord : examRecords) {
    String errorQuestionIds = examRecord.getErrorQuestionIds();
    if (!StringUtils.isEmpty(errorQuestionIds)) {
        String[] split = errorQuestionIds.split(",");
        for (String s : split) {
            quesIds.add(Integer.valueOf(s));
        }
    }
}

// 获取题库信息
QuestionBank bank = questionBankMapper.selectById(bankId);
// 根据题库和错题记录查询单选、多选、判断题列表
List<Question> questions = null;
if (CollectionUtils.isEmpty(quesIds)) {
    questions = questionMapper.selectList(
            new QueryWrapper<Question>().like("qu_bank_name",
                    bank.getBankName()).in("qu_type", 1, 2, 3));
} else {
    questions = questionMapper.selectList(
            new QueryWrapper<Question>().like("qu_bank_name",
                    bank.getBankName()).in("qu_type", 1, 2, 3)
                    .in("id", quesIds));
}
return questions;