在Java中对数据进行分组

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

public class GroupingExample {
    public static void main(String[] args) {
        // 假设有一组学生数据，每个学生有姓名和年龄两个属性
        List<Student> students = Arrays.asList(
                new Student("Alice", 18),
                new Student("Bob", 20),
                new Student("Charlie", 18),
                new Student("David", 20)
        );

        // 按照年龄进行分组
        Map<Integer, List<Student>> groupedByAge = students.stream()
                .collect(Collectors.groupingBy(Student::getAge));

        // 输出分组结果
        for (Map.Entry<Integer, List<Student>> entry : groupedByAge.entrySet()) {
            int age = entry.getKey();
            List<Student> group = entry.getValue();
            System.out.println("年龄为 " + age + " 的学生有：" + group);
        }
    }

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

        public Student(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 name;
        }
    }
}