Can you help me with a java code

Question

This code i made them i don't know if that is correct.

Person.Java

public class Person {
private String fname;
private String lname;
public Person(){
    this.fname="";
    this.lname="";

}
public Person(String fname,String lname){

    this.fname = fname;
    this.lname = lname;
}
public void setfirstname(String fname){
    this.fname = fname;

}
public void setlastname(String lname)
{
    this.lname = lname;

}
public String getfirstname(){
    return fname;
}
public String getlastname(){
    return lname;
}
}

Student.java

public class Student extends Person{
    private String studentid;
    private String studenttype;
    public Student(){
     this.studentid = "";
     this.studenttype = "";

    }
    public Student(String studentid,String studenttype)
    {
        this.studentid = studentid;
        this.studenttype = studenttype;
    }
    public void setStudentId(String studentid)
    {
        this.studentid = studentid;
    }
    public void setStudentType(String studenttype){
        this.studenttype = studenttype;
    }   
    public String getStudentID(){
        return studentid;
    }
    public String getStudentType()
    {
        return studenttype;
    }
}

Course.java
Course.java
i think i am not finish at this point i have some problem on the subject and list can you help me in this code

public class Course extends Student{
  private String courseid;
  private String coursedesc;
  private Subject subject[];
  public Course()
  {
   this.courseid = "";
    this.coursedesc = "";
  }
  public Course(String courseid,String coursedesc)
  {
    this.courseid = courseid;
    this.coursedesc = coursedesc;
  }
  public void setCourseId(String courseid)
  {
      this.courseid = courseid;
  }
  public void setCourseDesc(String coursedesc)
  {
      this.coursedesc = coursedesc;
  }
  public String getCourseId()
  {
   return courseid;   
  }
  public String getCourseDesc()
  {
   return coursedesc;   
  }
    public void addSubject(Subject subject)
    {

    }
   }

Subject.java
**Can you guys help me at this ? **

Answer 1

Use ArrayList<Subject> instead of Subject[]. Like that:

public class Course extends Student {
    private String courseid;
    private String coursedesc;
    private List<Subject> subjects;

    public Course()
    {
        this.courseid = "";
        this.coursedesc = "";
        subjects = new ArrayList<Subject>();
    }

    public Course(String courseid, String coursedesc)
    {
        this();
        this.courseid = courseid;
        this.coursedesc = coursedesc;
    }

    public void setCourseId(String courseid)
    {
        this.courseid = courseid;
    }

    public void setCourseDesc(String coursedesc)
    {
        this.coursedesc = coursedesc;
    }

    public String getCourseId()
    {
        return courseid;   
    }

    public String getCourseDesc()
    {
        return coursedesc;   
    }

    public void addSubject(Subject subject)
    {
        subjects.add(subject);
    }

    public List<Subject> getSubjects()
    {
        return subjects;
    }
}