从Java中的另一个类访问私有变量

Question

我正在使用Test类中的main方法，并尝试调用对象Course中的函数。这是我的主要方法的代码：

if (decideStatus > .75) {
                status = Classification.GRAD;
                gradCount++;
                if (gpa > 3.2) {
                    Student newStudent = new Student(sID, status, gpa);
                    **addStudentToRoster(newStudent);**
                } else {
                    gradRejectCount++;
                }

我正在尝试使用addStudentToRoster函数将newStudent添加到私有变量

public class Course {
    private int number = 0;
    private String title = "";
    private int capacity = 0;
    //won't compile with float type for cutoff
    private float cutoff = 0;
    private ArrayList<Student> roster = new ArrayList<>();
    private ArrayList<Student> waitlist = new ArrayList<>();

    public Course(int number, String name, int maxSize, float cutoff) {
        //set value of private fields
        this.number = number;
        this.title = name;
        this.capacity = maxSize;
        this.cutoff = cutoff;
    }

    public void addStudentToRoster(Student student) {
        roster.add(student);
    }

addStudentToRoster（newStudent）行有一个错误，指出该类的方法未定义。有谁知道我会如何解决这个问题？

Answer 1

自＆＃34; addStudentToRoster＆＃34;在Course类中定义，您需要创建该类的实例并将问题行代码修改为：

Course comp101 = new Course(1, "comp101", 80, 2.0);
comp101.addStudentToRoster(newStudent);