📚 Education based system

📌 Project Overview

This project is a University Course Enrollment and Student Grading System built in Java. It demonstrates strong Object-Oriented Programming (OOP) design, robust exception handling, Java Collections, and Generics & Wildcards.

The system manages:

• Student registration and profiles
• Course registration and capacity management
• Student enrollment in courses with duplicate prevention
• Grade assignment with validation
• Academic performance tracking and GPA calculation

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🎯 Objectives

• Model real-world university entities using OOP principles
• Enforce business rules through custom exception handling
• Use Java Collections for data management and integrity
• Implement Generic classes and Wildcard methods for type safety and reusability
• Build an interactive menu-driven system with full input validation

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🏗️ Project Structure

UniversityEnrollmentSystem/
│
├── entities/
│   ├── Person.java              (Abstract base class)
│   ├── Student.java             (Student entity)
│   ├── Instructor.java          (Instructor entity)
│   ├── Course.java              (Course entity)
│   └── Enrollment.java          (Links Student and Course)
│
├── exceptions/
│   ├── UniversitySystemException.java       (Base custom exception)
│   ├── DuplicateEnrollmentException.java    (Duplicate enrollment error)
│   ├── InvalidGradeException.java           (Invalid grade error)
│   ├── StudentNotFoundException.java        (Student not found error)
│   ├── CourseNotFoundException.java         (Course not found error)
│   └── NotEnrolledException.java            (Not enrolled error)
│
├── services/
│   ├── Repository.java          (Generic interface)
│   ├── GenericRepository.java   (Generic implementation)
│   ├── StudentService.java      (Student business logic)
│   ├── CourseService.java       (Course business logic)
│   └── EnrollmentService.java   (Enrollment business logic)
│
└── Main.java                    (Interactive menu-driven entry point)

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🧠 OOP Concepts Implemented

1. Encapsulation

• All fields are declared private
• Access controlled through getters and setters
• Input validation inside setter methods

2. Abstraction

• Person is an abstract class
• Contains abstract methods getRole() and displayInfo()
• Forces subclasses to provide their own implementation

3. Inheritance

• Student extends Person
• Instructor extends Person
• Reuses common properties like name, email, and ID

4. Polymorphism

• displayInfo() behaves differently for Student and Instructor
• Demonstrated using a Person[] array in Main

5. Relationship Modeling

• Student HAS-MANY Enrollments (One-to-Many)
• Course HAS-MANY Enrollments (One-to-Many)
• Enrollment LINKS Student and Course (Many-to-Many Association)
• Instructor HAS-MANY Courses (One-to-Many)

6. Separation of Concerns

• Entity classes handle data only
• Service classes handle business logic
• Main class handles user interaction
• Exception classes handle error reporting

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⚠️ Exception Handling

Custom Exception Hierarchy

RuntimeException (Java built-in - Unchecked)
└── UniversitySystemException (Custom base exception)
    ├── DuplicateEnrollmentException
    ├── InvalidGradeException
    ├── StudentNotFoundException
    ├── CourseNotFoundException
    └── NotEnrolledException

Business Rules Enforced

Rule	Exception Thrown
Student cannot enroll in the same course twice	DuplicateEnrollmentException
Grade must be between 0.0 and 5.0	InvalidGradeException
Cannot enroll non-existent student	StudentNotFoundException
Cannot enroll in non-existent course	CourseNotFoundException
Cannot grade a student not enrolled in the course	NotEnrolledException
Cannot enroll when course is full	UniversitySystemException
Cannot register duplicate student or course	UniversitySystemException

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📦 Java Collections Usage

Collection	Where Used	Purpose
ArrayList	Student, Course, Enrollment lists	Ordered storage of entities
HashMap	GenericRepository	Fast O(1) lookup by ID
List interface	Service return types	Flexible collection handling
Optional	Repository findById	Safe null handling

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🔧 Generics & Wildcards

Generic Interface

public interface Repository<T> {
    void add(T entity);
    Optional<T> findById(String id);
    List<T> findAll();
    boolean exists(String id);
}

Generic Class

public class GenericRepository<T> implements Repository<T> {
    private Map<String, T> storage;
    // Works with Student, Course, or any entity type
}

Upper Bounded Wildcard

public void addAll(List<? extends T> entities) {
    // Accepts any list of T or its subclasses
}

Lower Bounded Wildcard

public void exportTo(List<? super T> destination) {
    // Exports to any list of T or its parent classes
}

Generic Methods with Predicates

public List<T> findWhere(Predicate<T> condition) {
    // Finds entities matching any condition
}

public int countWhere(Predicate<? super T> condition) {
    // Counts entities matching any condition
}

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📊 GPA Scale (0 - 5)

GPA Range	Letter Grade	Classification
4.5 - 5.0	A+	First Class Honours
4.0 - 4.4	A	First Class Honours
3.5 - 3.9	B+	Second Class Upper
3.0 - 3.4	B	Second Class Lower
2.5 - 2.9	C+	Second Class Lower
2.0 - 2.4	C	Pass
1.5 - 1.9	D	Pass
1.0 - 1.4	E	Fail
0.0 - 0.9	F	Fail

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🖥️ Interactive Menu

╔════════════════════════════════════════════╗
║            MAIN MENU                       ║
╚════════════════════════════════════════════╝
  1. Register Student
  2. Register Course
  3. Enroll Student in Course
  4. Assign Grade to Student
  5. View All Students
  6. View All Courses
  7. View Student Details
  8. View Course Details
  9. View Student Academic Summary
 10. View System Statistics
  0. Exit

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✅ Input Validation

Input Type	Validation Rules
Student ID	Cannot be empty
Student Name	Letters, spaces, and hyphens only
Email	Must contain '@' and '.' with valid format
Credit Hours	Must be between 1 and 6
Course Capacity	Must be between 1 and 100
Grade	Must be between 0.0 and 5.0
Menu Choice	Must be a valid number within range

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▶️ How to Run the Project

Compile

javac Main.java

Run

java Main

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🧪 Test Scenarios

Test 1: Happy Path

1. Register 3 students
2. Register 2 courses
3. Enroll students in courses
4. Assign grades
5. View academic summaries and statistics

Test 2: Duplicate Enrollment Prevention

1. Register a student and a course
2. Enroll the student in the course
3. Try to enroll the same student in the same course again
4. System catches DuplicateEnrollmentException

Test 3: Course Full Prevention

1. Register a course with capacity of 2
2. Enroll 2 students successfully
3. Try to enroll a 3rd student
4. System catches UniversitySystemException with COURSE_FULL error

Test 4: Invalid Grade Prevention

1. Enroll a student in a course
2. Try to assign a grade above 5.0 or below 0.0
3. System catches InvalidGradeException

Test 5: Not Enrolled Prevention

1. Register a student and a course
2. Try to assign a grade without enrolling first
3. System catches NotEnrolledException

Test 6: Non-existent Entity Prevention

1. Try to enroll a non-existent student (e.g., ID: S999)
2. System catches StudentNotFoundException
3. Try to enroll in a non-existent course (e.g., Code: CS999)
4. System catches CourseNotFoundException

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📁 Requirements

• Java 8 or higher
• No external libraries required

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📈 Evaluation Criteria Coverage

Criteria	Marks	How It's Demonstrated
Class Design & Structure	2.5	5 entity + 5 service classes with clear responsibilities
Encapsulation	2.5	All fields private with controlled access
Inheritance & Abstraction	2.5	Person abstract class with Student and Instructor
Relationship Modeling	5	Student-Enrollment, Course-Enrollment, Instructor-Course
Separation of Concerns	2.5	Entity, Service, Exception, and Main layers
Custom Exceptions	0.5	6 custom exceptions with hierarchy
Correct Use of try-catch	1	All operations wrapped in proper try-catch
Validation & Error Triggers	1	Input validation before every operation
Clarity of Error Messages	0.5	Clear messages with error codes
Choice of Data Structures	1	HashMap for fast lookup and ArrayList for ordered data
Data Integrity	2	No duplicates and consistent state enforcement
Operations on Collections	1	Filter, search, iterate, add, and remove
Use in Real Context	1	Collections used realistically for academic records
Generic Classes/Methods	5	Repository interface and GenericRepository class
Type Safety	5	Compile-time type checking with no raw types
Wildcard Usage	5	Upper bounded and Lower bounded wildcards
Reusability	5	Same repository works for any entity type

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👨‍💻 Author

University Course Enrollment System Developed to demonstrate OOP, Exception Handling, Java Collections, and Generics & Wildcards

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📝 License

This project is for educational purposes only.