Code of Library Management System

Let's write the code for the designed classes in different languages.

We'll cover the following

Library management
Wrapping up

We’ve gone over the different aspects of the library management system and observed the attributes attached to the problem using various UML diagrams. Let us now explore the more practical side of things, where we will work on implementing the library management system using multiple languages. This is usually the last step in an object-oriented design interview process.

We have chosen the following languages to write the skeleton code of the different classes present in the library management system:

Java
C#
Python
C++
JavaScript

Library management#

In this section, we will provide the skeleton code of the classes designed in the class diagram lesson.

Note: For simplicity, we are not defining getter and setter functions. The reader can assume that all class attributes are private and accessed through their respective public getter methods and modified only through their public method functions.

Enumerations#

First, we will define all the enumerations required in the library management system. According to the class diagram, there are four enumerations used in the system: BookFormat, BookStatus, ReservationStatus, and AccountStatus. The code to implement these enumerations is as follows:`

Note: JavaScript does not support enumerations, so we will be using the Object.freeze() method as an alternative that freezes an object and prevents further modifications.

// definition of enumerations used in library management system
enum BookFormat {
    HARDCOVER,
    PAPERBACK,
    AUDIOBOOK,
    EBOOK,
    NEWSPAPER,
    MAGAZINE,
    JOURNAL
}
enum BookStatus {
    AVAILABLE,
    RESERVED,
    LOANED,
    LOST
}
enum ReservationStatus {
    WAITING,
    PENDING,
    CANCELED,
    NONE
}
enum AccountStatus {
    ACTIVE,
    CLOSED,
    CANCELED,
    BLACKLISTED,
    NONE

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Enum definitions

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The Address and Person classes

// User is an abstract class
public abstract class User {
    private String id;
    private String password;
    private AccountStatus status;
    private Person person;
    private LibraryCard card;
    public abstract boolean resetPassword();
}
public class Librarian extends User {
    public boolean addBookItem(BookItem bookItem);
    public boolean blockMember(Member member);
    public boolean unBlockMember(Member member);
    public boolean resetPassword() {
        // definition
    }
    public boolean addBookItem(BookItem bookItem) {
        // definition
    }
}
public class Member extends User {
    private Date dateOfMembership;
    private int totalBooksCheckedOut;
    public boolean reserveBookItem(BookItem bookItem);
    private void incrementTotalBooksCheckedOut();
    public boolean checkoutBookItem(BookItem bookItem); 
    private void checkForFine(String bookItemId);

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User and its child classes

public class BookReservation {
    private String itemId;
    private Date creationDate;
    private ReservationStatus status;
    private String memberId;
    public static BookReservation fetchReservationDetails(String bookItemId);
}
public class BookLending {
    private String itemId;
    private Date creationDate;
    private Date dueDate;
    private Date returnDate;
    private String memberId;
    private BookReservation bookReservation;
    private User user;
    public static boolean lendBook(String bookItemId, String memberId);
    public static BookLending fetchLendingDetails(String bookItemId);
}
public class Fine {
    private Date creationDate;
    private String bookItemId;
    private String memberId;
    public static void collectFine(String memberId, long days);
}

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The BookReservation, BookLending and Fine classes

// User is an abstract class
public abstract class Book {
    private String isbn;
    private String title;
    private String subject;
    private String publisher;
    private String language;
    private int numberOfPages;
    private BookFormat bookFormat;
    private List<Author> authors;
}
public class BookItem {
    private String id;
    private boolean isReferenceOnly;
    private Date borrowed;
    private Date dueDate;
    private double price;
    private BookStatus status;
    private Date dateOfPurchase;
    private Date publicationDate;
    private Rack placedAt;
    private Book book;  // Agggregation: BookItem has a reference to a Book
    
    // Constructors, getters, and other existing methods...
    public boolean checkout(String memberId) {
        // Implementation for checkout logic
        // Update the status, set due date, etc.
        // Return true if checkout is successful, false otherwise
        return true;  // Placeholder, replace with actual logic

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The Book, BookItem and Rack classes

// User is an abstract class
public abstract class Notification {
    Private String notificationId;
    Private Date creationDate;
    Private String content;
    private BookLending bookLending;
    private BookReservation bookReservation;
    public abstract boolean sendNotification();
}
public class PostalNotification extends Notification {
    private Address address;
    public boolean sendNotification(){
        // definition
    }
}
public class EmailNotification extends Notification {
    private String email;
    public boolean sendNotification(){
        // definition
    }
}

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Notification and its derived classes

public interface Search {
    // Interface method (does not have a body)
    public List<Book> searchByTitle(String title);
    public List<Book> searchByAuthor(String author);
    public List<Book> searchBySubject(String subject);
    public List<Book> searchByPublicationDate(Date publishDate);
}
public class Catalog implements Search {
    private HashMap<String, List<Book>> bookTitles;
    private HashMap<String, List<Book>> bookAuthors;
    private HashMap<String, List<Book>> bookSubjects;
    private HashMap<String, List<Book>> bookPublicationDates;
    public List<Book> searchByTitle(String query) {
        // definition
    }
    public List<Book> searchByAuthor(String query) {
        // definition
    }
    public List<Book> searchBySubject(String query) {
        // definition
    }
    public List<Book> searchByPublicationDate(String query) {
        // definition
    }
}

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The Search interface and the Catalog class

public class Library
{
  private String name;
  private Address address;
// Private constructor to prevent external instantiation
  private Library() {}
  public Address getAddress();
// The Library is a singleton class that ensures it will have only one active instance at a time
  private static Library library = null;
// Created a static method to access the singleton instance of Library class
  public static Library getInstance ()
  {
  if (library == null)
    {
    library = new Library ();
    }
  return library;
  }
}

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The Library class

Activity Diagram for the Library Management System

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