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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。