java - 是否可以通过此方法返回或以某种方式访问​​ "courses"中的数据？

Question

我正在做我的第一个 Java 编程作业，我还有另一个问题。我将 Course[] 放在 Student[] 内，但现在似乎遇到 NullPointerException 错误，我不明白为什么。

public Student[] analyzeData() {
    Scanner inputStream = null;

    try {
        inputStream = new Scanner(new FileInputStream("Programming Assignment 1 Data.txt"));
    } catch (FileNotFoundException e) {
        System.out.println("File Programming Assignment 1 Data.txt could not be found or opened.");
        System.exit(0);
    }

    int numberOfStudents = inputStream.nextInt();
    int tuitionPerHour = inputStream.nextInt();

    Student[] students = new Student[numberOfStudents];
    for (int i = 0; i < numberOfStudents; i++) {
        String firstName = inputStream.next();
        String lastName = inputStream.next();
        int studentID = inputStream.nextInt();
        String isTuitionPaid = inputStream.next();
        int numberOfCourses = inputStream.nextInt();


        Course[] courses = new Course[numberOfCourses];
        for (i = 0; i < numberOfCourses; i++) {
            String courseName = inputStream.next();
            String courseNumber = inputStream.next();
            int creditHours = inputStream.nextInt();
            String grade = inputStream.next();
            Course currentCourse = new Course(courseName, courseNumber, creditHours, grade);
            courses[i] = currentCourse;
        }
        Student currentStudent = new Student(firstName, lastName, studentID, isTuitionPaid, numberOfCourses, courses);
        students[i] = currentStudent;
    }
    return students;
}

输入文件的格式为:

3 345
Lisa Miller 890238 Y 2 
Mathematics MTH345 4 A
Physics PHY357 3 B


Bill Wilton 798324 N 2
English ENG378 3 B
Philosophy PHL534 3 A

其中courses 包含有关类(class)的信息，students 包含有关学生的信息。

Answer 1

文件的自然对象映射将是一个 Student 对象列表，每个对象都包含一个 Course 对象列表。 courses 数组应存储在学生对象内。