Java groupingBy:使用单流获取两个(或更多)组

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class GroupingByExample {
    public static void main(String[] args) {
        List<Person> persons = Arrays.asList(
                new Person("Alice", 20),
                new Person("Bob", 25),
                new Person("Charlie", 30),
                new Person("Alice", 35)
        );

        Map<String, List<Person>> groups = persons.stream()
                .collect(Collectors.groupingBy(Person::getName));

        System.out.println("按姓名分组：");
        groups.forEach((name, group) -> System.out.println(name + ": " + group));

        Map<String, List<Person>> ageGroups = persons.stream()
                .collect(Collectors.groupingBy(Person::getName,
                        Collectors.filtering(p -> p.getAge() > 30, Collectors.toList())));

        System.out.println("按姓名分组并过滤年龄大于30的人：");
        ageGroups.forEach((name, group) -> System.out.println(name + ": " + group));
    }

    static class Person {
        private String name;
        private int age;

        public Person(String name, int age) {
            this.name = name;
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public int getAge() {
            return age;
        }

        @Override
        public String toString() {
            return "Person{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    '}';
        }
    }
}

按姓名分组：
Alice: [Person{name='Alice', age=20}, Person{name='Alice', age=35}]
Bob: [Person{name='Bob', age=25}]
Charlie: [Person{name='Charlie', age=30}]
按姓名分组并过滤年龄大于30的人：
Alice: [Person{name='Alice', age=35}]
Bob: []
Charlie: []