singleton class· schoolcourseenrolmentsystem

dataManager.java

dataManager is the only place the program reads and writes files. It keeps the five in-memory lists, loads them from pipe-delimited text files at start-up and writes them back.

public class dataManager

Admin session

Pattern: Singleton via synchronized getInstance()
Delimiter: | (pipe), lists use commas
Files: students, instructors, administrators, courses, assessments
Missing file: Prints a message and starts with an empty list

Responsibilities#

Load all data at start-up and save it on exit
Hold the single copy of every list
Add, remove and look up students, instructors, admins, courses and grades
Keep IDs and course codes unique
Enrolment statistics and the most-popular-course report

Fields & enums#

Type Name Modifiers Line

dataManager instance private static L8

List<Instructor> instructors private L11

List<Administrator> administrators private L12

List<Student> students private L13

List<Course> courses private L14

List<Assessment> grades private L15

String STUDENTS_FILE private static final L19

String INSTRUCTORS_FILE private static final L20

String ADMINISTRATORS_FILE private static final L21

String COURSES_FILE private static final L22

String ASSESSMENTS_FILE private static final L23

String DELIMITER private static final L24

Type	Name	Modifiers	Line
`dataManager`	`instance`	private static	L8
`List<Instructor>`	`instructors`	private	L11
`List<Administrator>`	`administrators`	private	L12
`List<Student>`	`students`	private	L13
`List<Course>`	`courses`	private	L14
`List<Assessment>`	`grades`	private	L15
`String`	`STUDENTS_FILE`	private static final	L19
`String`	`INSTRUCTORS_FILE`	private static final	L20
`String`	`ADMINISTRATORS_FILE`	private static final	L21
`String`	`COURSES_FILE`	private static final	L22
`String`	`ASSESSMENTS_FILE`	private static final	L23
`String`	`DELIMITER`	private static final	L24

Constructors#

dataManager()DefaultL27
Package-private constructor: creates the five empty lists and prints “Testing Constructor”. Use getInstance() instead.

1 method

Singleton#

dataManager getInstance()staticL36
Create the single instance on first use and return it afterwards.

12 methods

Load & save#

void loadAllData()packageL44
Load students, instructors, administrators, courses, then assessments.
- Students load before courses, so saved course codes cannot be resolved (see Known issues)
void saveAllData()L53
Write all five lists back to their files.
void loadStudents()privateL63
Read students.txt. Each line needs at least 7 fields.
- Prints every line it loads
void saveStudents()packageL107
Write students.txt, joining enrolled course codes with commas.
void loadInstructors()privateL136
Read instructors.txt. Each line needs at least 6 fields.
void saveInstructors()packageL162
Write instructors.txt.
void loadAdministrators()privateL181
Read administrators.txt. Each line needs at least 6 fields.
void saveAdministrators()privateL206
Write administrators.txt.
void loadCourses()privateL225
Read courses.txt, resolving instructor and student IDs. Each line needs at least 8 fields.
void saveCourses()packageL267
Write courses.txt, joining enrolled student IDs with commas.
void loadAssessments()privateL299
Read assessments.txt. Each line needs at least 5 fields.
void saveAssessments()privateL325
Write assessments.txt.

4 methods

Students#

void addStudent(Student student)L342
Add if the ID is unique, then save students.txt.
boolean removeStudent(String studentId)L356
Remove by ID, then save students.txt.
Student getStudentById(String studentId)L372
Look up a student, or null.
List<Student> getAllStudents()L381
The live student list.

4 methods

Instructors#

void addInstructor(Instructor instructor)L386
Add if the ID is unique, then save instructors.txt.
boolean removeInstructor(String instructorId)L401
Remove by ID, clear it from any course it taught, then save both files.
Instructor getInstructorById(String instructorId)L422
Look up an instructor, or null.
List<Instructor> getAllInstructors()L431
The live instructor list.

3 methods

Administrators#

void addAdministrator(Administrator admin)L437
Add if the ID is unique, then save administrators.txt.
- Called at start-up to register the default admin
Administrator getAdminById(String adminId)L451
Look up an administrator, or null.
List<Administrator> getAllAdministrators()L460
The live administrator list.

4 methods

Courses#

void addCourse(Course course)L465
Add if the course code is unique.
boolean removeCourse(String courseCode)L481
Remove a course by code.
Course getCourseByCode(String courseCode)L500
Look up a course, or null.
List<Course> getAllCourses()L509
The live course list.

4 methods

Assessments#

void addAssessment(Assessment assessment)L514
Add a grade record.
void updateAssessment(String studentId, String courseCode, Assessment.ExamType examType, double score)L524
Update a matching grade or record a new one.
List<Assessment> getAssessmentsByStudentAndCourse(String studentId, String courseCode)L542
Every grade for one student in one course.
List<Assessment> getAllAssessments()L553
The live grade list.

4 methods

Uniqueness#

boolean isStudentIdUnique(String studentId)privateL558
No student already has this ID.
boolean isInstructorIdUnique(String instructorId)privateL562
No instructor already has this ID.
boolean isAdminIdUnique(String adminId)privateL565
No administrator already has this ID.
boolean isCourseCodeUnique(String courseCode)privateL569
No course already has this code.

6 methods

Operations & reports#

void assignInstructorToCourse(String courseCode, String instructorId)L574
Assign by course code and instructor ID, then save courses.
void enrollStudentInCourse(String studentId, String courseCode)L599
Enrol by IDs and save both files if it worked.
void dropStudentFromCourse(String studentId, String courseCode)L618
Drop by IDs and save both files if it worked.
void closeCourse(String courseCode)L639
Close a course by code and save courses.
void viewEnrollmentStatistics()L657
Per-course counts, total enrolled, and whether any course is open.
void generateReports()L676
Print the most popular course, or “No enrollments found.”

Known issues#

bugSaved enrolments are lost when students load

dataManager.java696 lines · from the project report

1package schoolcourseenrolmentsystem;

3import java.io.*;
4import java.util.*;

6public class dataManager {

  private static dataManager instance = null;

  // Main data lists
  private List<Instructor> instructors;
  private List<Administrator> administrators;
  private List<Student> students;
  private List<Course> courses;
  private List<Assessment> grades;

  // File paths

  private static final String STUDENTS_FILE = "students.txt";
  private static final String INSTRUCTORS_FILE = "instructors.txt";
  private static final String ADMINISTRATORS_FILE = "administrators.txt";
  private static final String COURSES_FILE = "courses.txt";
  private static final String ASSESSMENTS_FILE = "assessments.txt";
  private static final String DELIMITER = "\\|";

  // Private constructor to prevent instantiation
  dataManager() {
      instructors = new ArrayList<>();
      administrators = new ArrayList<>();
      students = new ArrayList<>();
      courses = new ArrayList<>();
      grades = new ArrayList<>();
      System.out.println("Testing Constructor");
  }

  public static synchronized dataManager getInstance() {
      if (instance == null) {
          instance = new dataManager();
      }
      return instance;
  }

  // Load all data from files
  void loadAllData() {
      loadStudents();
      loadInstructors();
      loadAdministrators();
      loadCourses();
      loadAssessments();
  }

  // Save all data to files
  public void saveAllData() {
      saveStudents();
      saveInstructors();

      saveAdministrators();
      saveCourses();
      saveAssessments();
  }

  // Load Students from file
  private void loadStudents() {
      try (BufferedReader reader = new BufferedReader(new FileReader(STUDENTS_FILE))) {
          String line;
          while ((line = reader.readLine()) != null) {
              System.out.println("Loading student: " + line);
              String[] parts = line.split(DELIMITER);
              if (parts.length >= 7) {
                  String name = parts[0];
                  String id = parts[1];
                  String password = parts[2];
                  String email = parts[3];
                  String phoneNumber = parts[4];
                  String address = parts[5];
                  int creditLimit = Integer.parseInt(parts[6]);

                  List<Course> enrolledCourses = new ArrayList<>();

                  if (parts.length > 7 && !parts[7].isEmpty()) {
                      String[] courseCodes = parts[7].split(",");
                      for (String code : courseCodes) {
                          Course course = getCourseByCode(code.trim());
                          if (course != null) {
                              enrolledCourses.add(course);
                          }
                      }
                  }
                  Student student = new Student(name, id, password, email, phoneNumber, address,
                          creditLimit,enrolledCourses);
                  System.out.println(student);
                  if (isStudentIdUnique(id)) {
                      students.add(student);

                  }
              }
          }
      } catch (FileNotFoundException e) {
          System.out.println("Students file not found. Starting with empty student list.");
      } catch (IOException e) {
          System.out.println("Error reading students file: " + e.getMessage());
      } catch (NumberFormatException e) {
          System.out.println("Error parsing student data: " + e.getMessage());
      }
  }
  // Save Students to file
  void saveStudents() {
      try (BufferedWriter writer = new BufferedWriter(new FileWriter(STUDENTS_FILE))) {
          for (Student student : students) {
              StringBuilder courseCodes = new StringBuilder();
              for (Course course : student.getEnrolledCoursesList()) {
                  if (courseCodes.length() > 0) {
                      courseCodes.append(",");
                  }
                  courseCodes.append(course.getCourseCode());
              }
              String line = String.join("|",
                      student.getName(),
                      student.getId(),
                      student.getPassword(),
                      student.getEmail(),
                      student.getPhoneNumber(),
                      student.getAddress(),
                      String.valueOf(student.getCreditLimit()),
                      courseCodes.toString());
              writer.write(line);
              writer.newLine();
          }
      } catch (IOException e) {
          System.out.println("Error writing students file: " + e.getMessage());
      }

  }

  // Load Instructors from file
  private void loadInstructors() {
      try (BufferedReader reader = new BufferedReader(new FileReader(INSTRUCTORS_FILE))) {
          String line;
          while ((line = reader.readLine()) != null) {
              String[] parts = line.split(DELIMITER);
              if (parts.length >= 6) {
                  String name = parts[0];
                  String id = parts[1];
                  String password = parts[2];
                  String email = parts[3];
                  String phoneNumber = parts[4];
                  String address = parts[5];
                  Instructor instructor = new Instructor(name, id, password, email, phoneNumber, address, new
                          ArrayList<>());
                  if (isInstructorIdUnique(id)) {
                      instructors.add(instructor);
                  }
              }
          }
      } catch (FileNotFoundException e) {
          System.out.println("Instructors file not found. Starting with empty instructor list.");
      } catch (IOException e) {
          System.out.println("Error reading instructors file: " + e.getMessage());
      }
  }
  // Save Instructors to file
  void saveInstructors() {
      try (BufferedWriter writer = new BufferedWriter(new FileWriter(INSTRUCTORS_FILE))) {
          for (Instructor instructor : instructors) {
              String line = String.join("|",
                      instructor.getName(),
                      instructor.getId(),
                      instructor.getPassword(),
                      instructor.getEmail(),

                      instructor.getPhoneNumber(),
                      instructor.getAddress());
              writer.write(line);
              writer.newLine();
          }
      } catch (IOException e) {
          System.out.println("Error writing instructors file: " + e.getMessage());
      }
  }
  // Load Administrators from file
  private void loadAdministrators() {
      try (BufferedReader reader = new BufferedReader(new FileReader(ADMINISTRATORS_FILE))) {
          String line;
          while ((line = reader.readLine()) != null) {
              String[] parts = line.split(DELIMITER);
              if (parts.length >= 6) {
                  String name = parts[0];
                  String id = parts[1];
                  String password = parts[2];
                  String email = parts[3];
                  String phoneNumber = parts[4];
                  String address = parts[5];
                  Administrator admin = new Administrator(name, id, password, email, phoneNumber, address);
                  if (isAdminIdUnique(id)) {
                      administrators.add(admin);
                  }
              }
          }
      } catch (FileNotFoundException e) {
          System.out.println("Administrators file not found. Starting with default admin.");
      } catch (IOException e) {
          System.out.println("Error reading administrators file: " + e.getMessage());
      }
  }
  // Save Administrators to file
  private void saveAdministrators() {
      try (BufferedWriter writer = new BufferedWriter(new FileWriter(ADMINISTRATORS_FILE))) {

          for (Administrator admin : administrators) {
              String line = String.join("|",
                      admin.getName(),
                      admin.getId(),
                      admin.getPassword(),
                      admin.getEmail(),
                      admin.getPhoneNumber(),
                      admin.getAddress());
              writer.write(line);
              writer.newLine();
          }
      } catch (IOException e) {
          System.out.println("Error writing administrators file: " + e.getMessage());
      }
  }
  // Load Courses from file
  private void loadCourses() {
      try (BufferedReader reader = new BufferedReader(new FileReader(COURSES_FILE))) {
          String line;
          while ((line = reader.readLine()) != null) {
              String[] parts = line.split(DELIMITER);
              if (parts.length >= 8) {
                  String courseName = parts[0];
                  String courseCode = parts[1];
                  String schedule = parts[2].isEmpty() ? null : parts[2];
                  String description = parts[3].isEmpty() ? null : parts[3];
                  Course.EnrollmentStatusEnum status = Course.EnrollmentStatusEnum.valueOf(parts[4]);
                  Instructor instructor = parts[5].isEmpty() ? null : getInstructorById(parts[5]);
                  int capacity = Integer.parseInt(parts[6]);
                  int creditHours = Integer.parseInt(parts[7]);
                  List<Student> enrolledStudents = new ArrayList<>();
                  if (parts.length > 8 && !parts[8].isEmpty()) {
                      String[] studentIds = parts[8].split(",");
                      for (String id : studentIds) {
                          Student student = getStudentById(id.trim());
                          if (student != null) {
                              enrolledStudents.add(student);

                          }
                      }
                  }
                  Course course = new Course(courseName, courseCode, schedule, description, status, instructor,
                          capacity, new ArrayList<>(), creditHours);
                  course.setEnrolledStudents(enrolledStudents);
                  if (isCourseCodeUnique(courseCode)) {
                      courses.add(course);
                  }
              }
          }
      } catch (FileNotFoundException e) {
          System.out.println("Courses file not found. Starting with empty course list.");
      } catch (IOException e) {
          System.out.println("Error reading courses file: " + e.getMessage());
      } catch (IllegalArgumentException e) {
          System.out.println("Error parsing course data: " + e.getMessage());
      }
  }
  // Save Courses to file
  void saveCourses() {
      try (BufferedWriter writer = new BufferedWriter(new FileWriter(COURSES_FILE))) {
          for (Course course : courses) {
              StringBuilder studentIds = new StringBuilder();
              for (Student student : course.getEnrolledStudents()) {
                  if (studentIds.length() > 0) {
                      studentIds.append(",");
                  }
                  studentIds.append(student.getId());
              }
              String instructorId = course.getInstructor() != null ? course.getInstructor().getId() : "";
              String schedule = course.getSchedule() != null ? course.getSchedule() : "";
              String description = course.getDescription() != null ? course.getDescription() : "";
              String line = String.join("|",
                      course.getCourseName(),
                      course.getCourseCode(),
                      schedule,

                      description,
                      course.getEnrollmentStatus().toString(),
                      instructorId,
                      String.valueOf(course.getCapacity()),
                      String.valueOf(course.getCreditHours()),
                      studentIds.toString());
              writer.write(line);
              writer.newLine();
          }
      } catch (IOException e) {
          System.out.println("Error writing courses file: " + e.getMessage());
      }
  }
  // Load Assessments from file
  private void loadAssessments() {
      try (BufferedReader reader = new BufferedReader(new FileReader(ASSESSMENTS_FILE))) {
          String line;
          while ((line = reader.readLine()) != null) {
              String[] parts = line.split(DELIMITER);
              if (parts.length >= 5) {
                  String studentId = parts[0];
                  String courseCode = parts[1];
                  Assessment.ExamType examType = Assessment.ExamType.valueOf(parts[2]);
                  double score = Double.parseDouble(parts[3]);
                  String assessmentName = parts[4];
                  Assessment assessment = new Assessment(studentId, courseCode, examType, score,
                          assessmentName);
                  grades.add(assessment);
              }
          }
      } catch (FileNotFoundException e) {
          System.out.println("Assessments file not found. Starting with empty assessment list.");
      } catch (IOException e) {
          System.out.println("Error reading assessments file: " + e.getMessage());
      } catch (IllegalArgumentException e) {
          System.out.println("Error parsing assessment data: " + e.getMessage());
      }

  }
  // Save Assessments to file
  private void saveAssessments() {
      try (BufferedWriter writer = new BufferedWriter(new FileWriter(ASSESSMENTS_FILE))) {
          for (Assessment assessment : grades) {
              String line = String.join("|",
                      assessment.getStudentId(),
                      assessment.getCourseCode(),
                      assessment.getExamType().toString(),
                      String.valueOf(assessment.getScore()),
                      assessment.getAssessmentName());
              writer.write(line);
              writer.newLine();
          }
      } catch (IOException e) {
          System.out.println("Error writing assessments file: " + e.getMessage());
      }
  }
  // Methods for Students
  public void addStudent(Student student) {
      if (student == null) {
          System.out.println("Error: Student cannot be null.");
          return;
      }
      if (isStudentIdUnique(student.getId())) {
          students.add(student);
          saveStudents();
          System.out.printf("Student added: %s with ID: %s%n", student.getName(), student.getId());
      } else {
          System.out.println("Error: Student ID " + student.getId() + " already exists.");
      }
  }

  public boolean removeStudent(String studentId) {
      Iterator<Student> iterator = students.iterator();
      while (iterator.hasNext()) {
          Student student = iterator.next();

          if (student.getId().equals(studentId)) {
              iterator.remove();
              saveStudents();
              System.out.printf("Student %s with ID: %s removed successfully.%n", student.getName(), studentId);
              return true;
          }
      }
      System.out.println("Student with ID: " + studentId + " not found.");
      return false;
  }

  public Student getStudentById(String studentId) {
      for (Student student : students) {
          if (student.getId().equals(studentId)) {
              return student;
          }
      }
      return null;
  }

  public List<Student> getAllStudents() {
      return students;
  }

  // Methods for Instructors
  public void addInstructor(Instructor instructor) {
      if (instructor == null) {
          System.out.println("Error: Instructor cannot be null.");
          return;
      }
      if (isInstructorIdUnique(instructor.getId())) {
          instructors.add(instructor);
          saveInstructors();
          System.out.printf("Instructor added: %s with ID: %s%n", instructor.getName(), instructor.getId());
      } else {
          System.out.println("Error: Instructor ID " + instructor.getId() + " already exists.");
      }

  }

  public boolean removeInstructor(String instructorId) {
      Iterator<Instructor> iterator = instructors.iterator();
      while (iterator.hasNext()) {
          Instructor instructor = iterator.next();
          if (instructor.getId().equals(instructorId)) {
              for (Course course : courses) {
                  if (course.getInstructor() != null && course.getInstructor().getId().equals(instructorId)) {
                      course.setInstructor(null);
                  }
              }
              iterator.remove();
              saveInstructors();
              saveCourses();
              System.out.printf("Instructor %s with ID: %s removed successfully.%n", instructor.getName(),instructorId);
              return true;
          }
      }
      System.out.println("Instructor with ID: " + instructorId + " not found.");
      return false;
  }

  public Instructor getInstructorById(String instructorId) {
      for (Instructor instructor : instructors) {
          if (instructor.getId().equals(instructorId)) {
              return instructor;
          }
      }
      return null;
  }

  public List<Instructor> getAllInstructors() {
      return instructors;
  }

  // Methods for Administrators

  public void addAdministrator(Administrator admin) {
      if (admin == null) {
          System.out.println("Error: Administrator cannot be null.");
          return;
      }
      if (isAdminIdUnique(admin.getId())) {
          administrators.add(admin);
          saveAdministrators();
          System.out.printf("Administrator added: %s with ID: %s%n", admin.getName(), admin.getId());
      } else {
          System.out.println("Error: Administrator ID " + admin.getId() + " already exists.");
      }
  }

  public Administrator getAdminById(String adminId) {
      for (Administrator admin : administrators) {
          if (admin.getId().equals(adminId)) {
              return admin;
          }
      }
      return null;
  }

  public List<Administrator> getAllAdministrators() {
      return administrators;
  }

  // Methods for Courses
  public void addCourse(Course course) {
      if (course == null) {
          System.out.println("Error: Course cannot be null.");
          return;
      }
      if (isCourseCodeUnique(course.getCourseCode())) {
          courses.add(course);
          saveCourses();

          System.out.printf("Course added: %s (%s) successfully.%n", course.getCourseName(),
                  course.getCourseCode());
      } else {
          System.out.println("Error: Course code " + course.getCourseCode() + " already exists.");
      }
  }

  public boolean removeCourse(String courseCode) {
      Iterator<Course> iterator = courses.iterator();
      while (iterator.hasNext()) {
          Course course = iterator.next();
          if (course.getCourseCode().equals(courseCode)) {
              for (Student student : course.getEnrolledStudents()) {
                  student.getEnrolledCoursesList().remove(course);
              }
              iterator.remove();
              saveCourses();
              saveStudents();
              System.out.printf("Course %s (%s) removed successfully.%n", course.getCourseName(), courseCode);
              return true;
          }
      }
      System.out.println("Course with code: " + courseCode + " not found.");
      return false;
  }

  public Course getCourseByCode(String courseCode) {
      for (Course course : courses) {
          if (course.getCourseCode().equals(courseCode)) {
              return course;
          }
      }
      return null;
  }

  public List<Course> getAllCourses() {
      return courses;

  }
  // =======================Methods for Assessments=======================
  public void addAssessment(Assessment assessment) {
      if (assessment == null) {
          System.out.println("Error: Assessment cannot be null.");
          return;
      }
      grades.add(assessment);
      saveAssessments();
      System.out.println("Assessment recorded successfully.");
  }

  public void updateAssessment(String studentId, String courseCode, Assessment.ExamType examType, double
          score) {
      for (Assessment assessment : grades) {
          if (assessment.getStudentId().equals(studentId) &&
                  assessment.getCourseCode().equals(courseCode) &&
                  assessment.getExamType() == examType) {
              assessment.setScore(score);
              saveAssessments();
              System.out.println("Assessment updated successfully.");
              return;
          }
      }
      Assessment newAssessment = new Assessment(studentId, courseCode, examType, score, examType.name());
      grades.add(newAssessment);
      saveAssessments();
      System.out.println("Assessment recorded successfully.");
  }

  public List<Assessment> getAssessmentsByStudentAndCourse(String studentId, String courseCode) {
      List<Assessment> studentAssessments = new ArrayList<>();
      for (Assessment assessment : grades) {
          if (assessment.getStudentId().equals(studentId) && assessment.getCourseCode().equals(courseCode)) {
              studentAssessments.add(assessment);
          }
      }

      return studentAssessments;
  }

  public List<Assessment> getAllAssessments() {
      return grades;
  }

  // Validation methods
  private boolean isStudentIdUnique(String studentId) {
      return students.stream().noneMatch(student -> student.getId().equals(studentId));
  }

  private boolean isInstructorIdUnique(String instructorId) {
      return instructors.stream().noneMatch(instructor -> instructor.getId().equals(instructorId));
  }
  private boolean isAdminIdUnique(String adminId) {
      return administrators.stream().noneMatch(admin -> admin.getId().equals(adminId));
  }

  private boolean isCourseCodeUnique(String courseCode) {
      return courses.stream().noneMatch(course -> course.getCourseCode().equals(courseCode));
  }

  //======================= Utility methods=======================
  public void assignInstructorToCourse(String courseCode, String instructorId) {
      Course course = getCourseByCode(courseCode);
      Instructor instructor = getInstructorById(instructorId);

      if (course == null) {
          System.out.println("Error: Course with code " + courseCode + " not found.");
          return;
      }
      if (instructor == null) {
          System.out.println("Error: Instructor with ID " + instructorId + " not found.");
          return;
      }

      if (course.getInstructor() == null) {
          course.setInstructor(instructor);
          saveCourses();
          System.out.printf("Instructor %s assigned to %s.%n", instructor.getName(), course.getCourseName());
      } else if (course.getInstructor().equals(instructor)) {
          System.out.printf("Instructor %s is already assigned to %s.%n", instructor.getName(),
                  course.getCourseName());
      } else {
          System.out.println("Course already has a different instructor assigned.");
      }
  }

  public void enrollStudentInCourse(String studentId, String courseCode) {
      Student student = getStudentById(studentId);
      Course course = getCourseByCode(courseCode);

      if (student == null) {
          System.out.println("Error: Student with ID " + studentId + " not found.");
          return;
      }
      if (course == null) {
          System.out.println("Error: Course with code " + courseCode + " not found.");
          return;
      }
      student.enroll_In_Course(course);
      if (course.getEnrolledStudents().contains(student)) {
          saveStudents();
          saveCourses();
      }
  }

  public void dropStudentFromCourse(String studentId, String courseCode) {
      Student student = getStudentById(studentId);
      Course course = getCourseByCode(courseCode);

      if (student == null) {
          System.out.println("Error: Student with ID " + studentId + " not found.");

          return;
      }
      if (course == null) {
          System.out.println("Error: Course with code " + courseCode + " not found.");
          return;
      }

      student.dropCourse(course);
      if (!course.getEnrolledStudents().contains(student)) {
          saveStudents();
          saveCourses();
      }
  }

  public void closeCourse(String courseCode) {
      Course course = getCourseByCode(courseCode);
      if (course == null) {
          System.out.println("Error: Course with code " + courseCode + " not found.");
          return;
      }

      if (course.getEnrolledStudents().size() >= course.getCapacity()) {
          System.out.println(course.getCourseName() + " is at full capacity.");
          course.setEnrollmentStatus(Course.EnrollmentStatusEnum.Closed);
      } else if (course.getEnrollmentStatus() == Course.EnrollmentStatusEnum.Closed) {
          System.out.println(course.getCourseName() + " enrollment status is already closed.");
      } else {
          System.out.println(course.getCourseName() + " still has available capacity.");
          course.setEnrollmentStatus(Course.EnrollmentStatusEnum.Closed);
      }
      saveCourses();
  }
  public void viewEnrollmentStatistics() {
      int totalEnrolled = 0;
      boolean openCoursesExist = false;

      System.out.println("\n---------Enrollment Statistics---------");

      for (Course course : courses) {
          int count = course.getEnrolledStudents() != null ? course.getEnrolledStudents().size() : 0;
          totalEnrolled += count;
          System.out.printf("Course: %s (%s) - Enrolled: %d%n", course.getCourseName(), course.getCourseCode(),
                  count);
          if (course.getEnrollmentStatus() == Course.EnrollmentStatusEnum.Open) {
              openCoursesExist = true;
          }
      }
      System.out.println("Total enrolled students across all courses: " + totalEnrolled);
      System.out.println("Open courses available: " + (openCoursesExist ? "Yes" : "No"));
  }

  public void generateReports() {
      System.out.println("\n---------Enrollment Report---------");

      Course mostPopular = null;
      int maxEnrolled = 0;

      for (Course course : courses) {
          int enrolled = course.getEnrolledStudents() != null ? course.getEnrolledStudents().size() : 0;
          if (enrolled > maxEnrolled) {
              mostPopular = course;
              maxEnrolled = enrolled;
          }
      }
      if (mostPopular != null) {
          System.out.printf("Most popular course: %s (%s) - Enrolled: %d.%n", mostPopular.getCourseName(),
                  mostPopular.getCourseCode(), maxEnrolled);
      } else {
          System.out.println("No enrollments found.");
      }
  }
696}

Responsibilities#

Fields & enums#

Constructors#

Singleton#

Load & save#

Students#

Instructors#

Administrators#

Courses#

Assessments#

Uniqueness#

Operations & reports#

Known issues#

Source