Lambda 对List集合多字段组合去重

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最新推荐文章于 2024-03-13 10:46:18 发布

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public static void main(String[] args) {
        List<QrCodeBaseDTO> saveDTOList = new ArrayList<>();

        QrCodeBaseDTO baseDTO = new QrCodeBaseDTO();
        baseDTO.setAppId("AppId1"); baseDTO.setAppName("AppName1");baseDTO.setAppValue(5);baseDTO.setAppType("AppType1"); saveDTOList.add(baseDTO);
        QrCodeBaseDTO baseDTO1 = new QrCodeBaseDTO();
        baseDTO1.setAppId("AppId1"); baseDTO1.setAppName("AppName1");baseDTO.setAppValue(5);baseDTO1.setAppType("AppType1"); saveDTOList.add(baseDTO1);
        QrCodeBaseDTO baseDTO2 = new QrCodeBaseDTO();
        baseDTO2.setAppId("AppId"); baseDTO2.setAppName("AppName2");baseDTO.setAppValue(5);baseDTO2.setAppType("AppType"); saveDTOList.add(baseDTO2);
        QrCodeBaseDTO baseDTO3 = new QrCodeBaseDTO();
        baseDTO3.setAppId("AppId"); baseDTO3.setAppName("AppName2");baseDTO.setAppValue(5);baseDTO3.setAppType("AppType"); saveDTOList.add(baseDTO3);
        QrCodeBaseDTO baseDTO4 = new QrCodeBaseDTO();
        baseDTO4.setAppId("AppId"); baseDTO4.setAppName("AppName4");baseDTO.setAppValue(5);baseDTO4.setAppType("AppType"); saveDTOList.add(baseDTO4);
        QrCodeBaseDTO baseDTO5 = new QrCodeBaseDTO();
        baseDTO5.setAppId("AppId"); baseDTO5.setAppName("AppName5");baseDTO.setAppValue(5);baseDTO5.setAppType("AppType"); saveDTOList.add(baseDTO5);

        System.out.println("最初多少个:" + saveDTOList.size());
        List<QrCodeBaseDTO> setList = saveDTOList.stream().collect(
                Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(user -> user.getAppId() + ";" + user.getAppName() + ";" + user.getAppType()))), ArrayList::new));
        System.out.println("去重后多少个:" + setList.size());

        //相同名字合并
        Map<String, Integer> saveDTOListMap = saveDTOList.stream().collect(Collectors.groupingBy(
                QrCodeBaseDTO ::getAppName, Collectors.summingInt(QrCodeBaseDTO ::getAppValue)));
    }

MultiValueMap<Date, Long> valueMap = new LinkedMultiValueMap<>();

int valuesize = valueMap.values().stream().map(List::size).reduce(Integer.valueOf(0), Integer::sum);