Assignment4.java

import java.io.*;
import java.util.*;

class Book implements Serializable, Comparable<Book> {
    private static final long serialVersionUID = 1L;
    private int bookId;
    private String title;
    private String author;
    private String category;
    private boolean isIssued;

    public Book(int bookId, String title, String author, String category) {
        this.bookId = bookId;
        this.title = title;
        this.author = author;
        this.category = category;
        this.isIssued = false;
    }

    public int getBookId() { return bookId; }
    public String getTitle() { return title; }
    public String getAuthor() { return author; }
    public String getCategory() { return category; }
    public boolean isIssued() { return isIssued; }

    public void markAsIssued() { this.isIssued = true; }
    public void markAsReturned() { this.isIssued = false; }

    public void displayBookDetails() {
        System.out.println("ID: " + bookId + ", Title: " + title + ", Author: " + author + ", Category: " + category + ", Status: " + (isIssued ? "Issued" : "Available"));
    }

    @Override
    public int compareTo(Book other) {
        return this.title.compareToIgnoreCase(other.title);
    }
}

class Member implements Serializable {
    private static final long serialVersionUID = 1L;
    private int memberId;
    private String name;
    private String email;
    private List<Integer> issuedBooks; 

    public Member(int memberId, String name, String email) {
        this.memberId = memberId;
        this.name = name;
        this.email = email;
        this.issuedBooks = new ArrayList<>();
    }

    public int getMemberId() { return memberId; }
    public String getName() { return name; }
    public List<Integer> getIssuedBooks() { return issuedBooks; }

    public void addIssuedBook(int bookId) { issuedBooks.add(bookId); }
    
    public boolean returnIssuedBook(int bookId) {
        return issuedBooks.remove(Integer.valueOf(bookId));
    }

    public void displayMemberDetails() {
        System.out.println("ID: " + memberId + ", Name: " + name + ", Email: " + email);
        System.out.println("Books Issued: " + issuedBooks.size() + " " + issuedBooks);
    }
}

class BookAuthorComparator implements Comparator<Book> {
    @Override
    public int compare(Book b1, Book b2) {
        return b1.getAuthor().compareToIgnoreCase(b2.getAuthor());
    }
}

class BookCategoryComparator implements Comparator<Book> {
    @Override
    public int compare(Book b1, Book b2) {
        return b1.getCategory().compareToIgnoreCase(b2.getCategory());
    }
}


public class Main {
    private Map<Integer, Book> books;
    private Map<Integer, Member> members;
    private Scanner scanner;
    private static final String BOOKS_FILE = "books.dat"; 
    private static final String MEMBERS_FILE = "members.dat";

    public Main() {
        books = new HashMap<>();
        members = new HashMap<>();
        scanner = new Scanner(System.in);
        loadFromFile();
    }

    private void loadFromFile() {
        try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(BOOKS_FILE))) {
            books = (Map<Integer, Book>) ois.readObject();
            System.out.println("Books loaded successfully from " + BOOKS_FILE);
        } catch (FileNotFoundException e) {
            System.out.println("Book data file not found. Starting with empty book collection.");
        } catch (IOException | ClassNotFoundException e) {
            System.out.println("Error loading book data: " + e.getMessage());
        }

        try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(MEMBERS_FILE))) {
            members = (Map<Integer, Member>) ois.readObject();
            System.out.println("Members loaded successfully from " + MEMBERS_FILE);
        } catch (FileNotFoundException e) {
            System.out.println("Member data file not found. Starting with empty member collection.");
        } catch (IOException | ClassNotFoundException e) {
            System.out.println("Error loading member data: " + e.getMessage());
        }
    }

    private void saveToFile() {
        try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(BOOKS_FILE))) {
            oos.writeObject(books);
            System.out.println("Books saved successfully to " + BOOKS_FILE);
        } catch (IOException e) {
            System.out.println("Error saving books: " + e.getMessage());
        }

        try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(MEMBERS_FILE))) {
            oos.writeObject(members);
            System.out.println("Members saved successfully to " + MEMBERS_FILE);
        } catch (IOException e) {
            System.out.println("Error saving members: " + e.getMessage());
        }
    }
    
    private int getNextId(Map<Integer, ?> map) {
        if (map.isEmpty()) return 101;
        return Collections.max(map.keySet()) + 1;
    }

    public void addBook() {
        int id = getNextId(books);
        System.out.print("Enter Book Title: ");
        String title = scanner.nextLine();
        System.out.print("Enter Author: ");
        String author = scanner.nextLine();
        System.out.print("Enter Category: ");
        String category = scanner.nextLine();

        Book newBook = new Book(id, title, author, category);
        books.put(id, newBook);
        saveToFile();
        System.out.println("Book added successfully with ID: " + id);
    }

    public void addMember() {
        int id = getNextId(members);
        System.out.print("Enter Member Name: ");
        String name = scanner.nextLine();
        System.out.print("Enter Email: ");
        String email = scanner.nextLine();

        Member newMember = new Member(id, name, email);
        members.put(id, newMember);
        saveToFile();
        System.out.println("Member added successfully with ID: " + id);
    }
    
    public void issueBook() {
        try {
            System.out.print("Enter Member ID: ");
            int memberId = scanner.nextInt();
            System.out.print("Enter Book ID to issue: ");
            int bookId = scanner.nextInt();
            scanner.nextLine(); 

            Member member = members.get(memberId);
            Book book = books.get(bookId);

            if (member == null) {
                System.out.println("Error: Member not found with ID " + memberId);
                return;
            }
            if (book == null) {
                System.out.println("Error: Book not found with ID " + bookId);
                return;
            }
            if (book.isIssued()) {
                System.out.println("Error: Book is already issued.");
                return;
            }

            book.markAsIssued();
            member.addIssuedBook(bookId);
            saveToFile();
            System.out.println("Book " + book.getTitle() + " issued to " + member.getName() + " successfully.");
        } catch (InputMismatchException e) {
            System.out.println("Error: Invalid input. IDs must be integers.");
            scanner.nextLine(); 
        }
    }

    public void returnBook() {
        try {
            System.out.print("Enter Member ID: ");
            int memberId = scanner.nextInt();
            System.out.print("Enter Book ID to return: ");
            int bookId = scanner.nextInt();
            scanner.nextLine(); 

            Member member = members.get(memberId);
            Book book = books.get(bookId);

            if (member == null) {
                System.out.println("Error: Member not found with ID " + memberId);
                return;
            }
            if (book == null) {
                System.out.println("Error: Book not found with ID " + bookId);
                return;
            }
            if (!book.isIssued()) {
                System.out.println("Error: Book was not marked as issued.");
                return;
            }

            if (member.returnIssuedBook(bookId)) {
                book.markAsReturned();
                saveToFile();
                System.out.println("Book " + book.getTitle() + " returned successfully by " + member.getName() + ".");
            } else {
                System.out.println("Error: This book was not recorded as issued to this member.");
            }
        } catch (InputMismatchException e) {
            System.out.println("Error: Invalid input. IDs must be integers.");
            scanner.nextLine(); 
        }
    }

    public void searchBooks() {
        System.out.println("\nSearch Books By:");
        System.out.println("1. Title");
        System.out.println("2. Author");
        System.out.println("3. Category");
        System.out.print("Enter choice: ");
        
        try {
            int choice = scanner.nextInt();
            scanner.nextLine(); 
            System.out.print("Enter search query: ");
            String query = scanner.nextLine().toLowerCase();

            List<Book> results = new ArrayList<>();
            for (Book book : books.values()) {
                boolean match = false;
                switch (choice) {
                    case 1: 
                        match = book.getTitle().toLowerCase().contains(query);
                        break;
                    case 2: 
                        match = book.getAuthor().toLowerCase().contains(query);
                        break;
                    case 3: 
                        match = book.getCategory().toLowerCase().contains(query);
                        break;
                    default:
                        System.out.println("Invalid search choice.");
                        return;
                }
                if (match) {
                    results.add(book);
                }
            }

            if (results.isEmpty()) {
                System.out.println("No books found matching the query.");
            } else {
                System.out.println("\n--- Search Results (" + results.size() + ") ---");
                for (Book book : results) {
                    book.displayBookDetails();
                }
            }
        } catch (InputMismatchException e) {
            System.out.println("Error: Invalid input. Choice must be an integer.");
            scanner.nextLine();
        }
    }

    public void sortBooks() {
        if (books.isEmpty()) {
            System.out.println("No books to sort.");
            return;
        }

        System.out.println("\nSort Books By:");
        System.out.println("1. Title (Default/Comparable)");
        System.out.println("2. Author (Comparator)");
        System.out.println("3. Category (Comparator)");
        System.out.print("Enter choice: ");

        try {
            int choice = scanner.nextInt();
            scanner.nextLine(); 
            
            List<Book> bookList = new ArrayList<>(books.values());
            Comparator<Book> comparator = null;

            switch (choice) {
                case 1: 
                    Collections.sort(bookList); // Uses Book's compareTo (by title)
                    System.out.println("Books sorted by Title.");
                    break;
                case 2: 
                    comparator = new BookAuthorComparator();
                    Collections.sort(bookList, comparator);
                    System.out.println("Books sorted by Author.");
                    break;
                case 3: 
                    comparator = new BookCategoryComparator();
                    Collections.sort(bookList, comparator);
                    System.out.println("Books sorted by Category.");
                    break;
                default:
                    System.out.println("Invalid sort choice.");
                    return;
            }

            System.out.println("\n--- Sorted Books ---");
            for (Book book : bookList) {
                book.displayBookDetails();
            }

        } catch (InputMismatchException e) {
            System.out.println("Error: Invalid input. Choice must be an integer.");
            scanner.nextLine(); 
        }
    }

    public void mainMenu() {
        int choice = 0;
        do {
            System.out.println("\n===== City Library Digital Management System =====");
            System.out.println("1. Add Book");
            System.out.println("2. Add Member");
            System.out.println("3. Issue Book");
            System.out.println("4. Return Book");
            System.out.println("5. Search Books");
            System.out.println("6. Sort Books");
            System.out.println("7. Exit & Save Data");
            System.out.print("Enter your choice: ");

            try {
                choice = scanner.nextInt();
                scanner.nextLine(); 

                switch (choice) {
                    case 1: addBook(); break;
                    case 2: addMember(); break;
                    case 3: issueBook(); break;
                    case 4: returnBook(); break;
                    case 5: searchBooks(); break;
                    case 6: sortBooks(); break;
                    case 7: 
                        System.out.println("Saving data and Exiting program. Thank you!");
                        break;
                    default:
                        System.out.println("Invalid choice. Please enter a number from 1 to 7.");
                }
            } catch (InputMismatchException e) {
                System.out.println("Error: Invalid input. Please enter a valid menu number.");
                choice = 0; 
                scanner.nextLine(); 
            }
        } while (choice != 7);
    }

    public static void main(String[] args) {
        Main manager = new Main();
        try {
            manager.mainMenu();
        } finally {
            if (manager.scanner != null) {
                manager.saveToFile();
                manager.scanner.close(); 
            }
            System.out.println("System resources released.");
        }
    }
}