src/CourseRegistrationStarter/Main.java

@@ -3,12 +3,24 @@ 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 c1 =new Course("Advanced Programming","AP1404",2);
+        Course c2 =new Course("Data Structures","DS2201",1);
+        Course c3=new Course("Database Systems","DB3301",3);
+
+        Student s1=new Student("Ali","402222001");
+
+        RegistrationSystem system= new RegistrationSystem();
+
+        system.addCourseToSystem(c1);
+        system.addCourseToSystem(c2);
+        system.addCourseToSystem(c3);
+
+        s1.addCourse(c1);
+        s1.addCourse(c2);
+
+        s1.dropCourse(c1);
+
+       s1.showRegisteredCourses();
+       system.showAllCourses();
     }
 }

src/CourseRegistrationStarter/RegistrationSystem.java

@@ -10,15 +10,25 @@ 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
+        for (Course c:courses){
+            System.out.println(
+                    c.getCourseName()+"-"+ c.getCourseCode()+"-capacity:"+c.getCapacity()
+            );
+        }
     }
 }

src/CourseRegistrationStarter/Student.java

@@ -5,6 +5,7 @@ public class Student {
     private String name;
     private String studentId;
     private ArrayList<Course> registeredCourses;
+    private int maxCourses = 3;
 
     public Student(String name, String studentId) {
         this.name = name;
@@ -21,19 +22,50 @@ public class Student {
     }
 
     public boolean addCourse(Course c) {
+        //bonus1:جلوگیری از ثبت نام تکراری
+        for (Course course : registeredCourses) {
+            if (course.getCourseCode().equals(c.getCourseCode())) {
+                return false;
+            }
+        }
+        //bonus2:محدودیت برای تکرار
+        if (registeredCourses.size() >= maxCourses) {
+            return false;
+        }
         // TODO: Register the student in the course if capacity allows
-        // Return true if registration was successful, otherwise false
+        if (c.getCapacity()>0){
+            registeredCourses.add(c);
+            c.reduceCapacity();
+            return true;
+        }
         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.contains(c)){
+            registeredCourses.remove(c);
+            c.increaseCapacity();
+            return true;
+        }
         return false;
     }
 
     public void showRegisteredCourses() {
         // TODO: Print all registered courses
+        System.out.println("Registered courses for"+name+":");
+        for (Course c :registeredCourses){
+            System.out.println(c.getCourseName()+"-"+ c.getCourseCode());
+        }
+    }
+    //bonus3
+    public Course findCourseByName(String name){
+
+        for (Course c: registeredCourses){
+            if (c.getCourseName().equalsIgnoreCase(name)){
+                return c;
+            }
+        }
+        return null;
     }
 }