ストリームを使用して Java オブジェクトを属性ごとにグループ化する方法

import java.util.*;
import java.util.stream.Collectors;

public class Grouping {
    public static void main(String[] args) {
        List<Student> studlist = new ArrayList<>();
        studlist.add(new Student("1726", "John", "New York"));
        studlist.add(new Student("4321", "Max", "California"));
        studlist.add(new Student("2234", "Andrew", "Los Angeles"));
        studlist.add(new Student("5223", "Michael", "New York"));
        studlist.add(new Student("7765", "Sam", "California"));
        studlist.add(new Student("3442", "Mark", "New York"));

        // Group the list by "Location" attribute using Streams
        Map<String, List<Student>> studlistGrouped =
                studlist.stream().collect(Collectors.groupingBy(w -> w.stud_location));

        // Print the results
        for (String location : studlistGrouped.keySet()) {
            System.out.println("Location: " + location);
            for (Student student : studlistGrouped.get(location)) {
                System.out.println("\t" + student.stud_id + " " + student.stud_name);
            }
        }
    }

    class Student {
        String stud_id;
        String stud_name;
        String stud_location;

        Student(String sid, String sname, String slocation) {
            this.stud_id = sid;
            this.stud_name = sname;
            this.stud_location = slocation;
        }
    }
}