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Data Manager (Code Reference)

The dataManager class is the persistence backbone of the School Enrollment System.
It handles loading, saving, and managing all system data using a simple text‑file storage approach.

This page provides a clean, structured reference to the class and its responsibilities.

Class Overview

The dataManager class is responsible for:

  • Maintaining lists of all system entities
  • Loading data from text files at startup
  • Saving data before program exit
  • Providing CRUD operations for:
  • Students
  • Instructors
  • Administrators
  • Courses
  • Assessments

It ensures that the system state persists across sessions.

Singleton Pattern

The class uses the singleton design pattern.

Key characteristics

  • Only one instance exists
  • Accessed through getInstance()
  • Ensures consistent data across all workflows
  • Prevents accidental duplication of data lists

This pattern is ideal for global system storage.

Data Lists

The class maintains the following in‑memory lists:

  • List<Student> listOfStudents
  • List<Instructor> listOfInstructors
  • List<Administrator> listOfAdministrators
  • List<Course> listOfCourses
  • List<Assessment> listOfAssessments

These lists represent the entire system’s data model.

File Paths

The class reads and writes to text files such as:

  • students.txt
  • instructors.txt
  • administrators.txt
  • courses.txt
  • assessments.txt

Each file stores serialized objects, one per line.

Loading Data

Method: loadAllData

Calls:

  • loadStudents()
  • loadInstructors()
  • loadAdministrators()
  • loadCourses()
  • loadAssessments()

Each loader:

  1. Opens the file
  2. Reads each line
  3. Splits fields using a delimiter
  4. Constructs the appropriate object
  5. Adds it to the corresponding list

If a file does not exist, it is created automatically.

Saving Data

Method: saveAllData

Calls:

  • saveStudents()
  • saveInstructors()
  • saveAdministrators()
  • saveCourses()
  • saveAssessments()

Each saver:

  1. Opens the file for writing
  2. Serializes each object into a delimited line
  3. Writes all lines to the file

This ensures all changes are preserved.

CRUD Operations

The class provides full CRUD support.

Students

  • Add student
  • Remove student
  • Update student
  • Retrieve student by ID

Instructors

  • Add instructor
  • Remove instructor
  • Update instructor
  • Retrieve instructor by ID

Administrators

  • Add administrator
  • Retrieve administrator by ID

Courses

  • Add course
  • Remove course
  • Update course
  • Assign instructor
  • Close course
  • Retrieve course by code

Assessments

  • Add assessment
  • Update assessment
  • Retrieve assessments for a student and course

These operations are used throughout the system by workflows and helper methods.

Utility Methods

Additional helper methods include:

  • Checking if a student or instructor exists
  • Ensuring unique IDs
  • Ensuring unique course codes
  • Validating instructor assignments
  • Checking if a course is full or open

These methods maintain data integrity.

Error Handling

The class uses exception handling to manage:

  • Missing files
  • Invalid data lines
  • I/O errors

If a file is missing:

  • A new empty file is created
  • The system continues without crashing

This ensures robustness.

Summary

The dataManager class is the core persistence layer of the School Enrollment System.
By managing all data lists, handling file I/O, and providing CRUD operations, it ensures that the system remains consistent, reliable, and easy to maintain.

This class supports every workflow and ties the entire system together.