如果我们要求map的顺序要按照list的执行的话,我们就要转map的时候指定map的具体实现。 Map<String, User> maps3 = list.stream().collect (Collectors.toMap(User::getName,Function.identity(),(k1, k2) -> k1,LinkedHashMap::new)); 输出结果 {pangHu=User{name='pangHu', age=18}, piKaQiu=User{name=...
mapList.add(map); } log.info("原始未分组mapList:{}", JSONUtil.toJsonStr(mapList)); // 通过name进行分组 Map<String, List<Map<String, Object>>> mapListGroupByName = mapList.stream().collect(Collectors.groupingBy(map -> map.get("name").toString())); log.info("分组后:{}", JSONUt...
stream().map(User::getAge).reduce(Integer::max); Optional<Integer> min = list.stream().map(User::getAge).reduce(Integer::min); println(sum); println(max); println(min); 统计IntSummaryStatistics statistics = students.stream().collect(Collectors.summarizingInt(User::getAge)); double average...
BigDecimal totalMoney = appleList.stream().map(Apple::getMoney).reduce(BigDecimal.ZERO, BigDecimal::add); System.err.println("totalMoney:"+totalMoney); //totalMoney:17.48 123 1. 2. 3. 4. 5.查找流中最大 最小值 Collectors.maxBy 和 Collectors.minBy 来计算流中的最大或最小值。 Optional<...
按照自定义Key分组 Map<String, List<User>> groupByDeptAppendName = users.stream().collect( Collectors.groupingBy( user -> user.getDept() + "&" + user.getName() ) ); 1. 2. 3. 4. 5. 多级分组 Map<String, Map<String, List<User>>> groupByDeptAndGender = users.stream() ...
); List<String> newList = list.stream().map(String::toUpperCase).collect(Collectors.toList())...
list.add(m1);list.add(m11);list.add(m12);//按bb进行分组统计Map<String,List<Map<String,Object>>>glist=list.stream().collect(Collectors.groupingBy(e->e.get("bb").toString()));glist.forEach((k,slist)->{Map<String,Object>nmap=newHashMap<>();IntSummaryStatistics sumcc=slist.stream()...
Map<String, Integer> sumResult = list.stream() .collect(Collectors.groupingBy(Item::getCategory, Collectors.reducing(0, Item::getQuantity, Integer::sum))); 这段代码会返回一个Map,其中键为分组的依据,值为对应列的求和结果。通过Collectors.reducing()方法,可以自定义初始值、映射函数和归约函数,实现对...
1. 分组 Map<String, List<SmsCustomerSendDetail>> collect = details.stream() .collect(Collectors.groupingBy(SmsCustomerSendDetail::getCustomerId)); 2. 单列求和 int totalValue = details.stream().mapToInt(SmsCustomerSendDetail::getSmsFee).sum(); ...