为什么我不能从特定 class 继承特定变量？

Question

I want to inherit the variable "remark" from the Student class to put into the Course Class. So I basically done the "extends" keyword and the super(remark), but it's still not working. Is is possible to inherit only 1 specific variable or is there another way?

public class Course extends Student   {
    
    private String[] courseName;
    private String[] courseNo;
    private int courseCredit;
    
    
    Course(String[] courseNo,String[] courseName,int courseCredit,char[] remark) {
        super(remark);
        this.courseNo = courseNo;
        this.courseName = courseName;
        this.courseCredit = courseCredit;
        
    }
    
    public void setCourseInfo(String[] courseNo,String[] courseName, int courseCredit) { 
        this.courseNo = courseNo;
        this.courseName = courseName;
        this.courseCredit = courseCredit;
        
    }
    
    public void setcourseName(String[] courseName) {
        this.courseName = courseName;
    }
    
    public void setcourseNo(String[] courseNo) {
        this.courseNo = courseNo;
    }
    
    public void setcourseCredit(int courseCredit) {
        this.courseCredit = courseCredit;
    }
    
    public String[] getcourseName() {
        return courseName;
    }
    
    public String[] getcourseNo() {
        return courseNo;
    }
    
    public int getcourseCredit() {
        return courseCredit;
    }

public class Student extends Person  {
    
    private int sid;
    private int numberOfCourse;
    private boolean isTuitionPaid;
    private String[] course;
    private char[] remark;
    
    Student(String fname,String lname,int sid,int numberOfCourse,boolean isTuitionPaid,String[] course,char[] remark) {
        
        super (fname,lname);
        this.sid = sid;
        this.numberOfCourse = numberOfCourse;
        this.isTuitionPaid = isTuitionPaid;
        this.course = course;
        this.remark = remark;
        
    }
    
    public void setInfo(String fname,String lname,int sid,int numberOfCourse,boolean isTuitionPaid,String[] course,char[] remark) {
        
        this.getfname();
        this.getlname();
        this.sid = sid;
        this.numberOfCourse = numberOfCourse;
        this.isTuitionPaid = isTuitionPaid;
        this.course = course;
        this.remark = remark;
        
    }
    
    public void setRemark(char[] remark) {
        this.remark = remark;
    }
    
    public char[] getRemark() {
        return remark;
    }
    
    public void setStudentID(int sid) {
        this.sid = sid;
    }
    
    public void setIsTuitionPaid(boolean isTuitionPaid) {
        this.isTuitionPaid = isTuitionPaid;
    }
    
    public void setNumberOfCourses(int numberOfCourse) {
        this.numberOfCourse = numberOfCourse;
    }
    
    public void setCoursesEnrolled(String[] courses,char[] remark) {
        this.course = courses;
        this.remark = remark;
    }
    
    public int getStudentID() {
        return sid;
    }
    
    public int getNumberOfCourses() {
        return numberOfCourse;
    }

Answer 1

If I understand your question, you'd want to restructure your code.

Here is one (traditional) way to do it with pseudocode to help you along but leave the learning to you.

The key concept to understand is inheritance. The typical question you would ask is using "is a." Is a Course a Student ? Is a Student a Course ? No. Then don't extend.

public class Course {
   //add getters and setters
   private String name; //multiple names may make your life harder, think it through
   private String[] number;
   private String description;
   private int credit; //are you sure this is an int??
   private Student[] enrolledStudents;
}

public class Student extends Person { //not sure whether Person is really needed, but that's based on your requirements.  Interfaces and composition are preferred.
   //add getters and setters
   private Course[] enrolledCourses;
   //other properties
 }

You would also need to get clearer on the Remark and the relationship to each class. Are remarks written about each student for each course? Do you need to see the remarks for all courses? Do you need to see all remarks for all students?

If the application is involved and uses say, a database, you could have a service class with something like:

public String getRemarks(Student student, Course course) {
    //some implementation.  A Remark could also be a class (bean) depending on your needs
}

Having a separate variable for numberOfCourses is likely not needed. You can just count the size of the enrolledCourses array.

Using Java's List will also make your life easier in many cases depending on what you need to do.

I will leave the functional style as a learning exercise, but that is where the industry has shifted toward in practice. Features of newer Java versions (eg records) can apply here too.