一道面试题，恳求大家帮助

[「已注销」]

题目：完成groupAndSort方法，对列表按照groupName分组，并对每个组内的数据按照value倒叙排序
public class A{
public String groupName;
public int value;
}

Map<String,List<A>> groupAndSort(List<A> list){


}

[benjor_ming]

Map<String, List<A>> collect = list.stream().sorted(Comparator.comparing(A::getValue)).collect(Collectors.groupingBy(A::getName));

[散着步的码农]

    Map<String, List<A>> groupAndSort(List<A> list){
        Map<String,List<A>> map = new HashMap<>();
        for (A a : list) {
            List<A> aList = map.get(a.groupName);
            if(aList==null){
                aList = new ArrayList<>();
            }
            aList.add(a);
            map.put(a.groupName,aList);
        }
        for (String s : map.keySet()) {
            List<A> finalList = map.get(s);
            finalList.sort(new Comparator<A>() {
                @Override
                public int compare(A o1, A o2) {
                    return o1.value>o2.value?-1:1;
                }
            });
        }

        return map;
    }

[K G]

这不就是排序吗？你做个工具包，要怎样排调一下