complete code

src/CourseRegistrationStarter/Main.java

@@ -2,13 +2,28 @@ package CourseRegistrationStarter;
 
 public class Main {
     public static void main(String[] args) {
-        // TODO:
-        // 1. Create at least 3 courses
-        // 2. Create 1 student
-        // 3. Create a registration system
-        // 4. Add courses to the system
-        // 5. Register the student in some courses
-        // 6. Drop one course
-        // 7. Print the final registered course list
+        Course course1 = new Course("Advanced Programming","AP1404", 2);
+        Course course2 = new Course("Data Structures","DS2201",1);
+        Course course3 = new Course("Database Systems","DB3301",3);
+
+        Student student1 = new Student("Ali" , "402222001");
+
+        RegistrationSystem registrationSystem = new RegistrationSystem();
+
+        registrationSystem.addCourseToSystem(course1);
+        registrationSystem.addCourseToSystem(course2);
+        registrationSystem.addCourseToSystem(course3);
+
+        student1.addCourse(course1);
+        student1.addCourse(course3);
+        student1.dropCourse(course1);
+
+        student1.showRegisteredCourses();
+
+        System.out.println("Course " + course1.getCourseName() + " capacity: " + course1.getCapacity());
+        System.out.println("Course " + course2.getCourseName() + " capacity: " + course2.getCapacity());
+        System.out.println("Course " + course3.getCourseName() + " capacity: " + course3.getCapacity());
+
+        System.out.println("the number of courses: " + student1.countCourse());
     }
 }

src/CourseRegistrationStarter/RegistrationSystem.java

@@ -9,16 +9,27 @@ public class RegistrationSystem {
     }
 
     public void addCourseToSystem(Course c) {
-        // TODO: Add the course to the system
+        courses.add(c);
     }
 
     public Course findCourseByCode(String code) {
-        // TODO: Search for a course by course code
-        // Return the matching course if found, otherwise return null
+        for(int i = 0 ; i < courses.size() ; i++){
+            Course course = courses.get(i);
+            if(course.getCourseCode().equals(code)){
+                return course;
+            }
+        }
         return null;
     }
 
     public void showAllCourses() {
-        // TODO: Print all courses in the system
+        System.out.println("Courses in the system: ");
+        for(int i = 0 ; i < courses.size() ; i++ ){
+            Course c = courses.get(i);
+            System.out.println(" Name: " + c.getCourseName() +
+                               " , code: " + c.getCourseCode() +
+                                ", capicity: " + c.getCapacity());
+
+        }
     }
 }

src/CourseRegistrationStarter/Student.java

@@ -1,4 +1,6 @@
 package CourseRegistrationStarter;
+import com.sun.net.httpserver.Authenticator;
+
 import java.util.ArrayList;
 
 public class Student {
@@ -21,19 +23,55 @@ public class Student {
     }
 
     public boolean addCourse(Course c) {
-        // TODO: Register the student in the course if capacity allows
-        // Return true if registration was successful, otherwise false
-        return false;
+        if(registeredCourses.contains(c)){
+            System.out.println( " already registered for " + c.getCourseName());
+            return false;
+        }
+        if(c.reduceCapacity()){
+            registeredCourses.add(c);
+            System.out.println("Successfully registered for " + c.getCourseName());
+            return true;
+
+        }
+        else{
+            System.out.println("Course is full");
+            return false;
+        }
     }
 
     public boolean dropCourse(Course c) {
-        // TODO: Remove the course from the student's list
-        // Restore the course capacity if removal was successful
-        // Return true if the course was dropped, otherwise false
-        return false;
+        boolean removed = registeredCourses.remove(c);
+        if(removed){
+            c.increaseCapacity();
+            System.out.println("Course " + c.getCourseName() + " succsessfully removed");
+            return true;
+        }
+        else{
+            System.out.println("Corse " + c.getCourseName() + "is not found");
+            return false;
+        }
     }
 
     public void showRegisteredCourses() {
-        // TODO: Print all registered courses
+        System.out.print("Courses registered by " + name + " : ");
+        if(registeredCourses.isEmpty()){
+            System.out.println("No course found! ");
+
+        }
+        else{
+            for(int i = 0 ; i < registeredCourses.size() ; i++ ){
+                Course course = registeredCourses.get(i);
+                System.out.println(course.getCourseName() + "(" + course.getCourseCode() + ")" + " , ");
+
+            }
+        }
     }
-}
+
+    public int countCourse(){
+        int count=0;
+        for(int i = 0 ; i < registeredCourses.size() ; i++){
+            count++;
+        }
+        return count;
+    }
+}