写在前面的话：减少strean流操作，减少多层嵌套for循环。使用普通for循环和map的方式进行转换，

第一步查询数据

List<Student> findList = studentDao.findList(findMap);

第二步准备遍历和赋值

if(CollectionUtil.isNotEmpty(findList)){// 第一次遍历，取出所有待翻译的字段，避免重复使用steam流取值Set<String> courseSet = new HashSet<>(16);Set<String> schooldSet = new HashSet<>(16);Set<String> nativePlaceSet = new HashSet<>(16);for (Student student : findList) {// 课程idString courseId = student.getSourceId();if(StringUtil.isNotEmpty(courseId)){courseSet.add(courseId);}// 学校idString schooldId = student.getSchoold();if(StringUtil.isNotEmpty(schooldId)){schooldSet.add(schooldId);}// 籍贯idString nativePlaceId = student.getNativePlace();if(StringUtil.isNotEmpty(nativePlaceId)){nativePlaceSet.add(nativePlaceId);}}// 查询课程信息、学校信息、籍贯信息，并转换成mapMap<String,Object> findMap = new HashMap<>(16);findMap.put("courseSet",courseSet);findMap.put("schooldSet",schooldSet);findMap.put("nativePlaceSet",nativePlaceSet);List<Course> courseList = courseDao.findList(findMap);List<Schoold> schooldList = schooldDao.findList(findMap);List<NativePlace> nativePlaceList = nativePlaceDao.findList(findMap);// 转换成mapMap<String,Course> courseMap = CollectionUtil.isEmpty(courseList) ? new HashMap<>(0) :courseList.stream().collect(Collectors.toMap(Course::getId, course -> course));Map<String,Schoold> schooldMap = CollectionUtil.isEmpty(schooldList) ? new HashMap<>(0) :courseList.stream().collect(Collectors.toMap(Schoold::getId, schoold -> schoold));Map<String,NativePlace> nativePlaceMap = CollectionUtil.isEmpty(nativePlaceList) ? new HashMap<>(0) :courseList.stream().collect(Collectors.toMap(NativePlace::getId, nativePlace -> nativePlace));// 第二次遍历，填充翻译后的值for (Student student : findList) {// 课程id-->课程名称String courseId = student.getSourceId();if(StringUtil.isNotEmpty(courseId)){student.setSourceName(courseMap.get(courseId).getName());}// 学校id-->学校名称String schooldId = student.getSchoold();if(StringUtil.isNotEmpty(schooldId)){student.setSchooldName(schooldMap.get(schooldId).getName());}// 籍贯id-->籍贯名称String nativePlaceId = student.getNativePlace();if(StringUtil.isNotEmpty(nativePlaceId)){student.setNativePlaceName(nativePlaceMap.get(nativePlaceId).getName());}}}

结语：仅遍历2次，减少了stream流取值。用转map的方式减少了多层for循环。

使用阿里的“通益千问”，指定java17将代码优化如下：

List<Student> findList = studentDao.findList(findMap);
if (CollectionUtil.isNotEmpty(findList)) {// 单次遍历收集所有ID（性能优化核心）Set<String> courseSet = new HashSet<>(16);Set<String> schoolSet = new HashSet<>(16);Set<String> nativePlaceSet = new HashSet<>(16);for (Student student : findList) {addIfNotEmpty(courseSet, student.getSourceId());addIfNotEmpty(schoolSet, student.getSchoold());addIfNotEmpty(nativePlaceSet, student.getNativePlace());}// 构建查询参数Map<String, Object> queryMap = new HashMap<>(16);queryMap.put("courseSet", courseSet);queryMap.put("schoolSet", schoolSet); // 修正拼写错误queryMap.put("nativePlaceSet", nativePlaceSet);// 查询关联数据List<Course> courseList = courseDao.findList(queryMap);List<School> schoolList = schoolDao.findList(queryMap); // 修正类名List<NativePlace> nativePlaceList = nativePlaceDao.findList(queryMap);// 转换为Map（使用辅助方法简化）Map<String, Course> courseMap = toMap(courseList, Course::getId);Map<String, School> schoolMap = toMap(schoolList, School::getId);Map<String, NativePlace> nativePlaceMap = toMap(nativePlaceList, NativePlace::getId);// 填充学生信息（使用Optional处理空值）for (Student student : findList) {// 课程ID → 课程名称String courseId = student.getSourceId();student.setSourceName(courseMap.getOrDefault(courseId, new Course()).getName());// 学校ID → 学校名称String schoolId = student.getSchoold();student.setSchooldName(schoolMap.getOrDefault(schoolId, new School()).getName());// 籍贯ID → 籍贯名称String nativePlaceId = student.getNativePlace();student.setNativePlaceName(nativePlaceMap.getOrDefault(nativePlaceId, new NativePlace()).getName());}
}// 辅助方法：简化字段添加逻辑
private void addIfNotEmpty(Set<String> set, String value) {if (StringUtil.isNotEmpty(value)) {set.add(value);}
}// 辅助方法：将列表转换为Map（避免重复代码）
private <T> Map<String, T> toMap(List<T> list, Function<T, String> keyExtractor) {return list.stream().collect(Collectors.toMap(keyExtractor, Function.identity(), (existing, replacement) -> existing));
}