判断集合是否为空

一：判断集合是否为空

if (CollectionUtils.isEmpty(equConnectTimeEverydays)) {
            
}

二：判断字符串，对象是否为空

if (StringUtils.isEmpty(equConnectTimeDay)) {
    
}

三：list分组

Map<String, List<EquConnectTimeEveryday>> collect = equConnectTimeEverydays.stream().collect(Collectors.groupingBy(EquConnectTimeEveryday::getEquId));

 四：对list统计

long workingHours = equConnectTimeEverydays.stream().mapToLong(EquConnectTimeEveryday::getLongTotalRunDuration).sum();