COMPLITTED

src/GraduateStudent.java

+import java.util.ArrayList;
+
+public class GraduateStudent extends Student {
+    private ArrayList<Publication> publications = new ArrayList<>();
+    private Professor advisor ;
+    public GraduateStudent(String firstName , String lastName , String id , int joiningYear , Department department , Professor advisor){
+        super(firstName , lastName , id , joiningYear , department);
+        this.advisor = advisor;
+    }
+
+    public ArrayList<Publication> getPublications() {
+        return publications;
+    }
+    public void addPublication (Publication p){
+        this.publications.add(p);
+    }
+}

src/Publication.java

+public class Publication {
+    private String title;
+    private int year;
+    public Publication(String title , int year){
+        this.title = title;
+        this.year = year;
+    }
+
+    public int getYear() {
+        return year;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+}

src/Student.java

+import java.util.ArrayList;
+
+public abstract class Student extends Person {
+    protected ArrayList<Course> courses = new ArrayList<>();
+    public Student (String firstName , String lastName , String id , int joiningYear , Department department){
+        super(firstName , lastName , id , joiningYear , department);
+    }
+
+    public ArrayList<Course> getCourses() {
+        return courses;
+    }
+    public void addCourse(Course c){
+        courses.add(c);
+    }
+}

src/UnderGradStudent.java

+public class UnderGradStudent extends Student {
+    public UnderGradStudent (String firstName , String lastName , String id , int joiningYear , Department department){
+        super(firstName , lastName , id , joiningYear , department);
+    }
+}