📚 Library Management System (Java)

Task 3 Library Management System (Using OOP)

A simple yet powerful Library Management System built in Java using Object-Oriented Programming (OOP) concepts. This project demonstrates Association, Aggregation, and Composition relationships between classes.

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✨ Features

• 📖 Book Management: Add books with ISBN, title, and author

• 👥 Member Management: Register members with contact details

• 🔄 Book Issuing: Issue books to members with borrowing limits

• 📅 Book Returning: Track return dates and update availability

• 🔒 Encapsulation: Secure data with private fields and controlled access

• 🧩 OOP Design: Strong class relationships (Aggregation/Composition)

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🏗️ Classes & Relationships

1. Book Class

public class Book {
    private final String ISBN;     // Unique ID [International Standard Book Number] (Immutable)
    private final String title;    // Book name  (Immutable)
    private final Author author;   // Association: Book HAS-A Author (Immutable)
    private boolean isAvailable;   // Availability status  
}

Relationship:

✅ Aggregation with Author (Author exists independently)

Method Used:

• isAvailable() → Check if book can be issued

• setAvailable() → Update availability (protected)

2. Author Class

   public class Author {
    private final String name;    // Immutable author name  
    private String email;         // Contact info  
}

Relationship:

✅ Association with Book (Multiple books per author)

Method Used:

• toString() → Prints name + email (e.g., J.K. Rowling [email protected])

3. Member class

  public class Member {
    private final String memberID;           // Unique ID  
    private final String name;               // Member name  
    private String email;                    //Member email
    private String contactNumber;            //Member contact      
    private List<BorrowingRecord> history;   // Aggregation: Member HAS-A records  
}

Relationships:

✅ Aggregation with BorrowingRecord (Records exist independently)

Method Used:

• canBorrowMoreBooks() → Check borrowing limit (max 5 books)
• addBorrowingRecord() → Add a new borrowing record

---Inner Class: BorrowingRecord---

public static class BorrowingRecord {
    private final Book book;       // Book borrowed  
    private LocalDate borrowDate;  // Issue date  
    private LocalDate returnDate;  // Return date (null if not returned)  
}

Relationship:

✅ Composition with Member (Records are part of Member’s lifecycle)

4. Library Class

public class Library {
    private final String libraryName;  // Library name  
    private List<Book> books;          // Aggregation: Library HAS-A Books  
    private List<Member> members;      // Aggregation: Library HAS-A Members  
}

Relationships: ✅ Aggregation with Book/Member (Both exist independently)

Method Used:

• addBook() → Add a new book

• registerMember() → Register a new member

• issueBook() → Issue a book to a member

• returnBook() → Return a book and update records

📤 issueBook() workflow:

  A[Find Member] --> B{Member Valid?}
  B -->|Yes| C[Find Book]
  C --> D{Book Available?}
  D -->|Yes| E[Create Record]
  E --> F[Update Status]

📤 returnBook() workflow:

  A[Find Record] --> B{Active Loan?}
  B -->|Yes| C[Set Return Date]
  C --> D[Mark Book Available]

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⚙️ How to Run

1. Compile all classes:

javac -d . *.java

2. Run tests:

java task3_LibraryManagementSystem.Library

3. Sample output:

=== ISSUING BOOK ===
Book issued successfully to Rohan Kumar for Clean Code: A Handbook of Agile Software Craftsmanship
Issued? true
Book available? false

=== ISSUING BOOK ===
Book issued successfully to Rohan Kumar for Spring in Action
Issued? true
Book available? false

=== RETURNING BOOK ===
Book returned successfully by Rohan Kumar for Clean Code: A Handbook of Agile Software Craftsmanship on 2025-09-26
Returned? true
Book available now? true

=== FAIL CASE ===
Book not found999
Failed return? false
Member's borrowing history size: 2
Record: Clean Code: A Handbook of Agile Software Craftsmanship borrowed on 2025-09-26, returned on 2025-09-26
Record: Spring in Action borrowed on 2025-09-26, returned on null

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🚀 Key OOP Concepts Applied

Concept ⬇️ | Where Used ⬇️ | Why Important? ⬇️

Encapsulation | All classes (private fields) | Prevents data corruption

Composition | BorrowingRecord in Member | Records die with Member

Aggregation | Books/Members in Library | Books exist without Library

Association | Book → Author | Loose coupling

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🌐 Project Structure:

task3_LibraryManagementSystem/
├── Book.java # Core entity
├── Author.java # Book's author
├── Member.java # With borrowing history
├── Library.java # System engine
└── README.md # THIS FILE! 🎉

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🛠️ Technologies Used

☕ Java 11+

⚙️ OOP Concepts: Encapsulation, Inheritance, Polymorphism

📚 Design Patterns: Aggregation, Composition, Association

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