Java8 -> Convert list to a map where list contains duplicate keys

Java8ListToMapWithDuplicateKeys

aList.stream()
        .collect(Collectors.groupingBy(AnObject::getKeyField, toDescSortedList()))
        .values()
        .stream()
        .map(list -> list.get(0))
        .collect(Collectors.toMap(AnObject::getKeyField, AnObject::getValueField));

private static <AnObject> Collector<AnObject,?,List<AnObject>> toDescSortedList() {
    return Collectors.collectingAndThen(
            Collectors.toCollection(ArrayList::new), list -> {
                list.sort(Comparator.comparing(AnObject::getUniqueField).reversed()); return list;
            } );
}