一、java8 Lambda 表达式的Stream 接口

分类：将list以某一个值分类

//将psnInsuWRList生成一个以InsuAdmdvs为key值的map数据）
List<PsnInsuDTO> psnInsuWRList = new ArrayList<>()；

Map<String, List<PsnInsuDTO>> psnInsuMap = 
psnInsuWRList.stream()
.collect(Collectors.groupingBy(PsnInsuDTO::getInsuAdmdvs));

过滤：将list以某一条件成立时重组为新的list

//取出标志为1的数据为一个新的list
personTypeDTOS = psnInsuWRList.stream()
.filter(personTypeDTO -> BusinessConst.VALI_FLAG_1_YX.equals(personTypeDTO.getValiFlag()))
.collect(Collectors.toList());

排序：将list以某一字段排序后重组为新的list

//以时间排序 reversed是倒序
personTypeList = psnInsuWRList.stream()
.sorted(Comparator.comparing(PersonTypeDTO::getTime).reversed())
.collect(Collectors.toList());

map：将数据根据需求处理后生成新的list

List<DataPermissionMenuDTO> list = dataPermMgtMenuDOs.stream().map(dataPermMgtMenuDO -> {
	DataPermissionMenuDTO dataPermissionMenuDTO = ObjectConversionUtil.convert(new DataPermissionMenuDTO(), dataPermMgtMenuDO);
	dataPermissionMenuDTO.setChildren(new LinkedList<>());
	map.put(dataPermMgtMenuDO.getMenuId(), 
	dataPermissionMenuDTO);
	return dataPermissionMenuDTO;
}).collect(Collectors.toList());

//将MedTreatAsClctYearsDTO 里psnno拿出单独生成一个list（distinct()去重）
List<String> psnNoList = medTreatAsClctYearsDTOList.stream()
.map(MedTreatAsClctYearsDTO :: getPsnNo)
.distinct().collect(Collectors.toList());

循环：循环list，处理list中的每个数据

psnInfoDTOList.stream()
.forEach(psnInfoDTO -> psnInfoDTO.setRecordCounts(psnInsuDOPageResult.getSize()));

二、sql的foreach使用

            <if test="servMattInstIdList != null and servMattInstIdList.size > 0">
                and
                <foreach collection="servMattInstIdList" separator="or" item="item" open="(" close=")">
                    <trim prefix="(" suffix=")">
                        SERV_MATT_INST_ID = #{item.psnNo}
                    </trim>
                </foreach>
            </if>

            <if test="execStatusList != null and execStatusList.size > 0">
                and EXEC_STATUS in
                <foreach collection="execStatusList" item="item" index="index" open="(" close=")" separator=",">
                    #{item}
                </foreach>
            </if>