编写一个学生成绩管理系统。学生的属性包括学号、姓名、年龄等。每个学生要学习若干课程，每门课程有平时成绩、期中考试成绩、实习成绩、期末考试成绩以及总评成绩等多个成绩，其中平时成绩的数目不定（因为不同课程的教师布置的平时作业不同），而总评成绩是其它成绩的平均值。请先设计合理的类存放这些信息，然后设计程序完成以下功能： （1）列出某个学生的所有成绩； （2）列出某门课程每个学生的总评成绩，及所有学生总评成绩的总评分； （3）分区段统计某门课程的学生总评成绩，例如60分以下的学生人数、60至70分的学生人数等。给出完整Java代码并写出设计思路

设计思路：

1. 设计一个Student类，包括学号、姓名、年龄等属性，以及学生所学习的课程列表。在Student类中添加方法addCourse，用于添加课程；getCourse，用于获取某门课程的成绩。

2. 设计一个Course类，包括课程名称、平时成绩、期中考试成绩、实习成绩、期末考试成绩以及总评成绩等属性。在Course类中添加方法calculateTotalScore，用于计算总评成绩。

3. 设计一个GradeManagementSystem类，用于实现程序功能。包括：添加学生、添加课程、查询某个学生的所有成绩、查询某门课程每个学生的总评成绩及所有学生总评成绩的总评分，分区段统计某门课程的学生总评成绩。

Java代码如下：

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Student {
    private String id;
    private String name;
    private int age;
    private Map<String, Course> courses;

    public Student(String id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.courses = new HashMap<>();
    }

    public void addCourse(Course course) {
        courses.put(course.getName(), course);
    }

    public List<Course> getAllCourses() {
        return new ArrayList<>(courses.values());
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }
}

public class Course {
    private String name;
    private List<Double> dailyScores;
    private double midtermScore;
    private double internshipScore;
    private double finalScore;
    private double totalScore;

    public Course(String name, List<Double> dailyScores, double midtermScore, double internshipScore, double finalScore) {
        this.name = name;
        this.dailyScores = dailyScores;
        this.midtermScore = midtermScore;
        this.internshipScore = internshipScore;
        this.finalScore = finalScore;
        this.totalScore = calculateTotalScore();
    }

    public String getName() {
        return name;
    }

    public double getTotalScore() {
        return totalScore;
    }

    private double calculateTotalScore() {
        double sum = midtermScore + internshipScore + finalScore;
        for (double score : dailyScores) {
            sum += score;
        }
        return sum / (dailyScores.size() + 3);
    }
}

public class GradeManagementSystem {
    private List<Student> students;

    public GradeManagementSystem() {
        this.students = new ArrayList<>();
    }

    public void addStudent(Student student) {
        students.add(student);
    }

    public void addCourseToStudent(String studentId, Course course) {
        for (Student student : students) {
            if (student.getId().equals(studentId)) {
                student.addCourse(course);
                break;
            }
        }
    }

    public List<Course> getAllCoursesOfStudent(String studentId) {
        for (Student student : students) {
            if (student.getId().equals(studentId)) {
                return student.getAllCourses();
            }
        }
        return null;
    }

    public double getAverageTotalScoreOfCourse(String courseName) {
        double sum = 0;
        int count = 0;
        for (Student student : students) {
            for (Course course : student.getAllCourses()) {
                if (course.getName().equals(courseName)) {
                    sum += course.getTotalScore();
                    count++;
                }
            }
        }
        if (count == 0) {
            return 0;
        }
        return sum / count;
    }

    public Map<String, Integer> getSectionCountOfCourse(String courseName, int interval) {
        Map<String, Integer> sectionCountMap = new HashMap<>();
        for (Student student : students) {
            for (Course course : student.getAllCourses()) {
                if (course.getName().equals(courseName)) {
                    int totalScore = (int) course.getTotalScore();
                    int section = totalScore / interval;
                    String key = section * interval + "-" + (section + 1) * interval;
                    sectionCountMap.put(key, sectionCountMap.getOrDefault(key, 0) + 1);
                }
            }
        }
        return sectionCountMap;
    }
}

在main函数中可以进行测试：

public static void main(String[] args) {
    GradeManagementSystem system = new GradeManagementSystem();

    // 添加学生
    Student student1 = new Student("001", "张三", 18);
    Student student2 = new Student("002", "李四", 19);
    system.addStudent(student1);
    system.addStudent(student2);

    // 添加课程
    Course course1 = new Course("Java", Arrays.asList(80.0, 85.0, 90.0), 85.0, 90.0, 95.0);
    Course course2 = new Course("Python", Arrays.asList(90.0, 95.0), 90.0, 85.0, 95.0);
    system.addCourseToStudent("001", course1);
    system.addCourseToStudent("001", course2);
    system.addCourseToStudent("002", course1);

    // 列出某个学生的所有成绩
    List<Course> courses = system.getAllCoursesOfStudent("001");
    for (Course course : courses) {
        System.out.println(course.getName() + "总评成绩：" + course.getTotalScore());
    }

    // 列出某门课程每个学生的总评成绩及所有学生总评成绩的总评分
    double average = system.getAverageTotalScoreOfCourse("Java");
    System.out.println("Java所有学生总评成绩的平均分：" + average);

    // 分区段统计某门课程的学生总评成绩
    Map<String, Integer> sectionCountMap = system.getSectionCountOfCourse("Java", 10);
    for (Map.Entry<String, Integer> entry : sectionCountMap.entrySet()) {
        System.out.println(entry.getKey() + "分段的学生人数：" + entry.getValue());
    }
}