Stream流相关方法

LIST<对象> 转换MAP 并根据某个字段分组

// 并根据某个字段分组，并做了归类
Map<String, List<User>> collect = users.stream().collect(Collectors.groupingBy(User::getUserName));

　Map<String, List<SqePartInfoDTO>> partInfoMapByPmxu = partInfoDTOS.stream().collect(Collectors.groupingBy(SqePartInfoDTO::getPmxu));

// 根据某字段分组
Map<String, SqePartInfoDo> collect = partInfoDoList.stream().collect(Collectors.toMap(SqePartInfoDo::getPartNo, SqePartInfoDo -> SqePartInfoDo));

//当根据某字段（getIssueDetailId），该字段对应的Do有重复时，可以用这种方式

Map<Long, PisIssueMeasuresDoV1> measuresDoByDetailIdMap = unfinishedMeasureProcessList.stream().collect(
            Collectors.toMap(PisIssueMeasuresDoV1::getIssueDetailId, PisIssueMeasuresDoV1 -> PisIssueMeasuresDoV1,(v1, v2) -> v1));

　　

List按某个字段排序

List<User> newList = list.stream().sorted(Comparator.comparing(User::getAge)).collect(Collectors.toList());

获取List<对象>中每个对象某个属性的集合 

List<String> partNos = list.stream().map(ApqpPartsStartConfigurationDo::getPartNo).collect(Collectors.toList());

// 对对象的属性做了去重
List<String> sSqeCodeList = records.stream().map(ApqpGroupBasicDo::getSSqeCode).distinct().collect(Collectors.toList());

Stream.filter:

//根据域账号分组
Map<String, ThirdSyncUserDTO> usersMapByWindowsAccount = allUsers.stream()
            .filter(item -> StringUtils.isNotBlank(item.getWindowsAccount()))
            .collect(Collectors.toMap(ThirdSyncUserDTO::getWindowsAccount, ThirdSyncUserDTO -> ThirdSyncUserDTO));

// 根据对象中某个字段进行排序，.reversed()降序
processInfoDTORespList = processInfoDTORespList.stream()
　　　　　　　　.sorted(Comparator.comparing(PisMalfunctionProcessInfoDTO::getRelationTime)
　　　　　　　　.reversed())
　　　　　　　　.collect(Collectors.toList());

stream流获取对象某个属性的最大和最小值:

PisIssueProcessDetailDo pisIssueProcessDetailDo = list.stream()
            .max(Comparator.comparing(PisIssueProcessDetailDo::getIssueVersion)).get();

// DEMO    
public static void main(String[] args) {

        List<PisIssueProcessDetailDo> list = new ArrayList<>();
        PisIssueProcessDetailDo issueProcessDetailDo01 = new PisIssueProcessDetailDo();
        issueProcessDetailDo01.setIssueId(1L);
        issueProcessDetailDo01.setIssueVersion(2L);
        PisIssueProcessDetailDo issueProcessDetailDo02 = new PisIssueProcessDetailDo();
        issueProcessDetailDo02.setIssueId(3L);
        issueProcessDetailDo02.setIssueVersion(3L);
        PisIssueProcessDetailDo issueProcessDetailDo03 = new PisIssueProcessDetailDo();
        issueProcessDetailDo03.setIssueId(2L);
        issueProcessDetailDo03.setIssueVersion(1L);
        PisIssueProcessDetailDo issueProcessDetailDo04 = new PisIssueProcessDetailDo();
        issueProcessDetailDo04.setIssueId(4L);
        issueProcessDetailDo04.setIssueVersion(0L);

        list.add(issueProcessDetailDo01);
        list.add(issueProcessDetailDo02);
        list.add(issueProcessDetailDo03);
        list.add(issueProcessDetailDo04);

        PisIssueProcessDetailDo pisIssueProcessDetailDo = list.stream()
            .max(Comparator.comparing(PisIssueProcessDetailDo::getIssueVersion)).get();
        PisIssueProcessDetailDo pisIssueProcessDetailDo1 = list.stream()
            .max(Comparator.comparing(PisIssueProcessDetailDo::getIssueId)).get();

        System.out.println(pisIssueProcessDetailDo);

    }