README.md

Low-Level-Design-using-OOD-principles-design-patterns-and-UML-diagrams

Examples of low level design of systems using object oriented principles incorporating design patterns and depicting Classes, Use Cases, Activity and Sequences using UML diagrams.

An example for a Low Level System Design would be as below:

Library management System

Requirements:

• R1: The system should be able to store the information about books and members of the library. Moreover, the complete log of the book borrowing process should also be stored.
• R2: Every book is supposed to have a unique identification number and other details including a rack number to help locate the book physically.
• R3: Every book should have an associated ISBN, title, author name, subject, and publication date.
• R4: There can be multiple copies of the book. Each copy will be recognized as a book item.
• R5: There can be two types of users, i.e., the librarian and the members.
• R6: Every user must have a library card with a unique card number.
• R7: One member can issue a maximum of 10 books at a time.
• R8: The member can issue a book for a maximum of 15 days.
• R9: Each book item can only be reserved by a single member.
• R10: The system should be able to keep a record of who issued or reserved a particular book and on which date.
• R11: The system should allow the user to renew the reserved book.
• R12: The system should send a notification if the book is not returned within the due date.
• R13: If the book is currently not available, then the member should be able to reserve it for whenever it is available.
• R14: The system should allow the user to search a book by its title, author name, subject, or publication date.

Use Case Diagram:

Class Diagram:

Sequence Diagrams:

Issue Book

Return Book (with opt Pay Fine)

Activity Diagrams:

Checkout Book

Return Book

Renew Book

Code:

package library_management_system;

import library_management_system.books.BookItem;
import library_management_system.books.BookLending;
import library_management_system.books.BookReservation;
import library_management_system.enums.BookStatus;
import library_management_system.users.Librarian;
import library_management_system.users.Member;

import java.time.LocalDate;
import java.util.Date;

public class Main {
    public static void main(String[] args) {
        Library library = Library.getInstance();
        Librarian librarian = new Librarian();
        Member member = new Member();

        BookItem bookItem1 = new BookItem();
        BookItem bookItem2 = new BookItem();

        librarian.addBookItem(bookItem1);
        librarian.addBookItem(bookItem2);

        boolean isAvailable = bookItem1.checkout(member.getId());
        if(isAvailable){
            BookReservation bookReservation = new BookReservation(bookItem1.getId(), new Date(), member.getId());
            BookLending bookLending = new BookLending(new Date(), new Date(), bookReservation, member);
            boolean canLend = BookLending.lendBook(bookItem1.getId(), member.getId());

            if(canLend){
                member.checkoutBookItem(bookItem1);
                bookItem1.setStatus(BookStatus.LOANED);
            }
            else
                System.out.println("Sorry cannot checkout requested book, " + bookItem1.getStatus());
        }
    }


}

References:

Library Management System