GroupBy之后的Java排序

Question

我怎样才能把这些分类成一张分类地图而不是一张地图呢

    class Person {
        String name;
        double weight;

        public Person(String name, double weight) {
            this.name = name;
            this.weight = weight;
        }

        public double getWeight() {
            return this.weight;
        }
    }
    List<Person> people = Arrays.asList(
            new Person("Alex", 150.0),
            new Person("Courtney", 120.0),
            new Person("Billy", 180.0)
            );

    Map<Double, List<Person>> grouped = people.stream()
            .collect(Collectors.groupingBy(Person::getWeight));

Answer 1

您可以在SortedMap中输入结果，如下所示：

final Map<Double, List<Person>> grouped = new TreeMap<>(
    people.stream().collect(Collectors.groupingBy(Person::getWeight)));

Answer 2

可以使用重载的^{}来获取供应商：

SortedMap<Double, List<Person>> grouped = people.stream()
        .collect(Collectors.groupingBy(
                Person::getWeight,
                TreeMap::new,
                Collectors.toList()));