Java 8 Streams Map在Group By之后减少的值

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

public class Main {
    public static void main(String[] args) {
        // 创建一个包含学生姓名和分数的列表
        List<Student> students = Arrays.asList(
                new Student("Alice", "Math", 80),
                new Student("Bob", "Math", 90),
                new Student("Alice", "English", 85),
                new Student("Bob", "English", 95)
        );

        // 按学生姓名进行分组，并计算每个学生的总分
        Map<String, Integer> totalScoresByStudent = students.stream()
                .collect(Collectors.groupingBy(Student::getName, Collectors.summingInt(Student::getScore)));

        System.out.println(totalScoresByStudent);
        // 输出结果: {Alice=165, Bob=185}
    }

    static class Student {
        private String name;
        private String subject;
        private int score;

        public Student(String name, String subject, int score) {
            this.name = name;
            this.subject = subject;
            this.score = score;
        }

        public String getName() {
            return name;
        }

        public String getSubject() {
            return subject;
        }

        public int getScore() {
            return score;
        }
    }
}