third

src/org/university/core/Professor.java

 package org.university.core;
 
+import java.util.ArrayList;
+
 public class Professor extends Employee{
+    private ArrayList<Course>courses;
+    private String group;
+    public Professor(String firstName, String lastName, String ID, int joiningYear, Department department, String position, double basicIncome,String group) {
+        super(firstName, lastName, ID, joiningYear, department, position, basicIncome);
+        courses=new ArrayList<>();
+        this.group=group;
+    }
+
+    public ArrayList<Course> getCourses() {
+        return courses;
+    }
 
+    public String getGroup() {
+        return group;
+    }
+    public void addCourse(Course c){
+        courses.add(c);
+    }
 
 }