src/main/java/models/Student.java

@@ -11,5 +11,20 @@ public class Student extends User {
         this.enrolledCourses = new ArrayList<>();
     }
 
-  //TODO
+    public void enrollCourse(Course course) {
+        this.enrolledCourses.add(course);
+    }
+    public void showMyCourses() {
+        for (Course course : this.enrolledCourses) {
+            System.out.println(course);
+        }
+    }
+    public Course getEnrolledCourses(int id) {
+        for (Course course : this.enrolledCourses) {
+            if (course.getId() == id) {
+                return course;
+            }
+        }
+        return null;
+    }
 }

src/main/java/services/SchoolSystem.java

@@ -16,7 +16,26 @@ public class SchoolSystem {
     }
 
     // ========== Student Management ==========
-   //TODO
+    public void registerStudent(String username, String password) {
+        Student student = new Student(username, password);
+        this.students.add(student);
+    }
+    public Student loginStudent(String username, String password) {
+        for (Student student : this.students) {
+            if (student.getUsername().equals(username) && student.checkPassword(password)) {
+                return student;
+            }
+        }
+        return null;
+    }
+    private Student findStudent(String username) {
+        for (Student student : this.students) {
+            if (student.getUsername().equals(username)) {
+                return student;
+            }
+        }
+        return null;
+    }
 
     // ========== Teacher Management ==========
     public boolean registerTeacher(String username, String password) {
@@ -44,12 +63,17 @@ public class SchoolSystem {
 
     // ========== Course Management ==========
     public boolean addCourseToSystem(String courseName) {
-        //TODO
+        Course course = new Course(courseName);
+        this.allCourses.add(course);
         return true;
     }
 
     public Course findCourseById(int id) {
-       //TODO
+       for  (Course course : this.allCourses) {
+           if(course.getId() == id) {
+               return course;
+           }
+       }
         return null;
     }