src/CourseRegistrationStarter/Main.java

@@ -2,13 +2,25 @@ 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 ap = new Course("Advanced Programing" , "AP1404" , 2);
+        Course ds = new Course("Data Structures" , "DS2201" , 1);
+        Course db = new Course("Database Systems" , "DB3301" , 3);
+
+        Student ali = new Student("Ali" , "402222001");
+
+        RegistrationSystem system = new RegistrationSystem();
+
+        system.addCourseToSystem(ap);
+        system.addCourseToSystem(ds);
+        system.addCourseToSystem(db);
+
+        ali.addCourse(ap);
+        ali.addCourse(ds);
+
+        ali.dropCourse(ds);
+
+        ali.showRegisteredCourses();
+
+        system.showAllCourses();
     }
 }

src/CourseRegistrationStarter/RegistrationSystem.java

@@ -9,16 +9,22 @@ 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(Course c : courses){
+            if(c.getCourseCode().equals(code)){
+                return c;
+            }
+        }
         return null;
     }
 
     public void showAllCourses() {
-        // TODO: Print all courses in the system
+        System.out.println("corses on system : ");
+        for(Course c : courses){
+            System.out.println(c.getCourseName() + "/" + c.getCourseCode() + " capacity :" + c.getCapacity());
+        }
     }
 }

src/CourseRegistrationStarter/Student.java

@@ -21,19 +21,37 @@ 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
+        if(registeredCourses.contains(c)){
+            System.out.println("Studend registered in this corse!");
+            return false;
+        }
+        if(c.reduceCapacity()){
+            registeredCourses.add(c);
+            System.out.println("corse added:" + c.getCourseName());
+            return true;
+        }
+        System.out.println("corse 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
+        if(registeredCourses.remove(c)){
+            c.increaseCapacity();
+            System.out.println("corse dropped :" + c.getCourseName());
+            return true;
+        }
+        System.out.println("studend is not registered in this corse!");
         return false;
     }
 
     public void showRegisteredCourses() {
-        // TODO: Print all registered courses
+        System.out.println("registered corses for " + name + ":");
+        if(registeredCourses.isEmpty()){
+            System.out.println("no corses registered");
+            return;
+        }
+        for(Course c : registeredCourses){
+            System.out.println("- " + c.getCourseName() + "/" + c.getCourseCode());
+        }
     }
 }