Java8-04

1.单字段分组

Map<String, List<TaskRecordDO>> collect1 = list.stream().collect(Collectors.groupingBy(TaskRecordDO::getOutNodeKey));

@Test
public void test13() {
    //所有价格等级的店铺列表
    Map<Integer, List<Property>> priceMap = properties.stream()
        .collect(Collectors.groupingBy(Property::getPriceLevel));
    System.out.println(JSON.toJSONString(priceMap));
}

2.多字段分组

//多字段
Map<String, List<DayStoreSkuSizeInvSalDTO>> financialYearWeekInfo = sizeIndex.stream().collect(Collectors.groupingBy(p -> p.getFinancialYear() + ":" + p.getFinancialWeek()));

3.每个店铺的价格等级

每个店铺的价格等级:

@Test
public void test12() {
    //获取每个店铺的价格等级
    Map<String, Integer> map = properties.stream()
        .collect(Collectors.toMap(Property::getName, Property::getPriceLevel));
    System.out.println(JSON.toJSONString(map));
}

4.多字段分组

分组:

Map<Integer, Map<Integer, List<StoreSalCalendarDTO>>> groupByYearMonth =               results.stream().collect(Collectors.groupingBy(StoreSalCalendarDTO::getFinancialYear,                       Collectors.groupingBy(StoreSalCalendarDTO::getFinancialYearMonth)));

遍历:

Map<Integer, Map<Integer, List<StoreSalCalendarDTO>>> groupByYearMonth = new HashMap<>();
        if (Objects.nonNull(groupByYearMonth)) {
            groupByYearMonth.forEach((year, yearValue) -> {
                if (Objects.nonNull(yearValue)) {
                    yearValue.forEach((month, monthValue) -> {
                    });
                }
            });
        }