public static void main(String[] args) {

Library library = Library.loadFromDisk();

library.runConsole();

library.saveToDisk();

System.out.println("Exiting. Data saved.");

}

private static final long serialVersionUID = 1L;

int id;

String title;

String author;

int totalQuantity;

int availableQuantity;

public Book(int id, String title, String author, int qty) {

this.id = id;

this.title = title;

this.author = author;

this.totalQuantity = qty;

this.availableQuantity = qty;

}

public String toString() {

return String.format("ID:%d | %s by %s | total:%d | available:%d", id, title, author, totalQuantity, availableQuantity);

}

private static final long serialVersionUID = 1L;

int bookId;

LocalDate issueDate;

LocalDate dueDate;

public IssueRecord(int bookId, LocalDate issueDate, LocalDate dueDate) {

this.bookId = bookId;

this.issueDate = issueDate;

this.dueDate = dueDate;

}

private static final long serialVersionUID = 1L;

String studentId; // unique

String name;

String password;

// Map bookId -> IssueRecord

Map<Integer, IssueRecord> issued = new HashMap<>();

public Student(String studentId, String name, String password) {

this.studentId = studentId;

this.name = name;

this.password = password;

}

public String toString() {

return String.format("%s (%s)", name, studentId);

}

private static final long serialVersionUID = 1L;

Map<Integer, Book> books = new HashMap<>();

Map<String, Student> students = new HashMap<>();

// admin credentials (simple)

String adminUser = "admin";

String adminPass = "admin123";

// configuration

static final int FINE_PER_DAY = 5; // currency units per day

static final int DEFAULT_ISSUE_DAYS = 14; // days allowed

transient Scanner scanner = new Scanner(System.in);

// filenames

static final String BOOKS_FILE = "books.dat";

static final String STUDENTS_FILE = "students.dat";

static final String LIBRARY_FILE = "library.dat";

// ---------- Console UI ----------

public void runConsole() {

System.out.println("Welcome to Student Library Management System");

boolean running = true;

while (running) {

System.out.println("\nMain Menu: 1) Admin Login 2) Student Login/Register 3) Search Books 4) Exit");

System.out.print("Choose option: ");

String ch = scanner.nextLine().trim();

switch (ch) {

case "1":

if (adminLogin()) {

adminMenu();

}

break;

case "2":

studentEntry();

break;

case "3":

searchBooksMenu();

break;

case "4":

running = false;

break;

default:

System.out.println("Invalid option.");

}

}

}

// ---------- Admin ----------

boolean adminLogin() {

System.out.print("Admin username: ");

String u = scanner.nextLine().trim();

System.out.print("Admin password: ");

String p = scanner.nextLine().trim();

if (u.equals(adminUser) && p.equals(adminPass)) {

System.out.println("Admin login successful.");

return true;

}

System.out.println("Wrong admin credentials.");

return false;

}

void adminMenu() {

boolean a = true;

while (a) {

System.out.println("\nAdmin Menu: 1) Add Book 2) Update Book 3) Search Books 4) View Issued Books 5) Logout");

System.out.print("Choose option: ");

String ch = scanner.nextLine().trim();

switch (ch) {

case "1":

addBookConsole();

break;

case "2":

updateBookConsole();

break;

case "3":

searchBooksMenu();

break;

case "4":

viewAllIssuedBooks();

break;

case "5":

a = false;

break;

default:

System.out.println("Invalid option.");

}

}

}

void addBookConsole() {

try {

System.out.print("Enter book ID (integer): ");

int id = Integer.parseInt(scanner.nextLine().trim());

if (books.containsKey(id)) {

System.out.println("Book with that ID already exists.");

return;

}

System.out.print("Enter title: ");

String title = scanner.nextLine();

System.out.print("Enter author: ");

String author = scanner.nextLine();

System.out.print("Enter quantity: ");

int qty = Integer.parseInt(scanner.nextLine().trim());

Book b = new Book(id, title, author, qty);

books.put(id, b);

System.out.println("Book added: " + b);

} catch (NumberFormatException e) {

System.out.println("Invalid number.");

}

}

void updateBookConsole() {

System.out.print("Enter book ID to update: ");

try {

int id = Integer.parseInt(scanner.nextLine().trim());

Book b = books.get(id);

if (b == null) {

System.out.println("Book not found.");

return;

}

System.out.println("Current: " + b);

System.out.print("New title (or press Enter to keep): ");

String t = scanner.nextLine();

if (!t.isEmpty()) {

b.title = t;

}

System.out.print("New author (or press Enter to keep): ");

String a = scanner.nextLine();

if (!a.isEmpty()) {

b.author = a;

}

System.out.print("Adjust total quantity (enter integer, can be negative to reduce): ");

String q = scanner.nextLine();

if (!q.isEmpty()) {

int delta = Integer.parseInt(q.trim());

int newTotal = b.totalQuantity + delta;

if (newTotal < 0) {

newTotal = 0;

}

// adjust available proportionally (naive)

int used = b.totalQuantity - b.availableQuantity;

b.totalQuantity = newTotal;

b.availableQuantity = Math.max(0, newTotal - used);

}

System.out.println("Updated: " + b);

} catch (NumberFormatException e) {

System.out.println("Invalid input.");

}

}

void viewAllIssuedBooks() {

System.out.println("\nIssued Books Report:");

boolean any = false;

for (Student s : students.values()) {

if (!s.issued.isEmpty()) {

any = true;

System.out.println("Student: " + s);

for (IssueRecord r : s.issued.values()) {

Book b = books.get(r.bookId);

System.out.printf(" Book: %s | Issued: %s | Due: %s | Fine(if today): %d\n",

(b == null ? "(deleted book)" : b.title),

r.issueDate.format(DateTimeFormatter.ISO_DATE),

r.dueDate.format(DateTimeFormatter.ISO_DATE),

calculateFine(r.dueDate, LocalDate.now()));

}

}

}

if (!any) {

System.out.println("No issued books currently.");

}

}

// ---------- Student registration / login ----------

void studentEntry() {

System.out.println("\n1) Register 2) Login 3) Back");

System.out.print("Choose: ");

String ch = scanner.nextLine().trim();

switch (ch) {

case "1":

registerStudentConsole();

break;

case "2":

studentLoginConsole();

break;

default:

return;

}

}

void registerStudentConsole() {

System.out.print("Enter student ID (unique): ");

String sid = scanner.nextLine().trim();

if (students.containsKey(sid)) {

System.out.println("Student ID already exists.");

return;

}

System.out.print("Enter name: ");

String name = scanner.nextLine();

System.out.print("Enter password: ");

String pass = scanner.nextLine();

Student s = new Student(sid, name, pass);

students.put(sid, s);

System.out.println("Registered: " + s);

}

void studentLoginConsole() {

System.out.print("Student ID: ");

String sid = scanner.nextLine().trim();

System.out.print("Password: ");

String pass = scanner.nextLine().trim();

Student s = students.get(sid);

if (s == null) {

System.out.println("No such student. Register first.");

return;

}

if (!s.password.equals(pass)) {

System.out.println("Wrong password.");

return;

}

System.out.println("Welcome, " + s.name);

studentMenu(s);

}

void studentMenu(Student s) {

boolean run = true;

while (run) {

System.out.println("\nStudent Menu: 1) Search Books 2) Issue Book 3) Return Book 4) My Issued Books 5) Logout");

System.out.print("Choose: ");

String ch = scanner.nextLine().trim();

switch (ch) {

case "1":

searchBooksMenu();

break;

case "2":

issueBookConsole(s);

break;

case "3":

returnBookConsole(s);

break;

case "4":

viewStudentIssued(s);

break;

case "5":

run = false;

break;

default:

System.out.println("Invalid option.");

}

}

}

// ---------- Search ----------

void searchBooksMenu() {

System.out.println("\nSearch by: 1) ID 2) Title keyword 3) Author keyword 4) Back");

System.out.print("Choose: ");

String ch = scanner.nextLine().trim();

switch (ch) {

case "1":

System.out.print("Enter ID: ");

try {

int id = Integer.parseInt(scanner.nextLine().trim());

Book b = books.get(id);

if (b != null) {

System.out.println(b);

}else {

System.out.println("Not found.");

}

} catch (NumberFormatException e) {

System.out.println("Invalid ID.");

}

break;

case "2":

System.out.print("Enter title keyword: ");

String tk = scanner.nextLine().toLowerCase();

books.values().stream().filter(b -> b.title.toLowerCase().contains(tk)).forEach(System.out::println);

break;

case "3":

System.out.print("Enter author keyword: ");

String ak = scanner.nextLine().toLowerCase();

books.values().stream().filter(b -> b.author.toLowerCase().contains(ak)).forEach(System.out::println);

break;

default:

return;

}

}

// ---------- Issue / Return ----------

void issueBookConsole(Student s) {

System.out.print("Enter book ID to issue: ");

try {

int id = Integer.parseInt(scanner.nextLine().trim());

String res = issueBook(s.studentId, id);

System.out.println(res);

} catch (NumberFormatException e) {

System.out.println("Invalid ID.");

}

}

String issueBook(String studentId, int bookId) {

Student s = students.get(studentId);

if (s == null) {

return "Student not found.";

}

Book b = books.get(bookId);

if (b == null) {

return "Book not found.";

}

if (b.availableQuantity <= 0) {

return "No copies available.";

}

if (s.issued.containsKey(bookId)) {

return "You already have this book issued.";

}

LocalDate issueDate = LocalDate.now();

LocalDate dueDate = issueDate.plusDays(DEFAULT_ISSUE_DAYS);

IssueRecord r = new IssueRecord(bookId, issueDate, dueDate);

s.issued.put(bookId, r);

b.availableQuantity -= 1;

saveToDisk();

return String.format("Issued '%s' to %s. Due on %s.", b.title, s.name, dueDate.format(DateTimeFormatter.ISO_DATE));

}

void returnBookConsole(Student s) {

System.out.print("Enter book ID to return: ");

try {

int id = Integer.parseInt(scanner.nextLine().trim());

String res = returnBook(s.studentId, id);

System.out.println(res);

} catch (NumberFormatException e) {

System.out.println("Invalid ID.");

}

}

String returnBook(String studentId, int bookId) {

Student s = students.get(studentId);

if (s == null) {

return "Student not found.";

}

IssueRecord r = s.issued.get(bookId);

if (r == null) {

return "This book is not issued to you.";

}

Book b = books.get(bookId);

if (b != null) {

b.availableQuantity += 1;

}

long fine = calculateFine(r.dueDate, LocalDate.now());

s.issued.remove(bookId);

saveToDisk();

if (fine > 0) {

return String.format("Returned. Fine due: %d (overdue %d days).", fine, ChronoUnit.DAYS.between(r.dueDate, LocalDate.now()));

}else {

return "Returned on time. No fine.";

}

}

void viewStudentIssued(Student s) {

if (s.issued.isEmpty()) {

System.out.println("You have no issued books.");

return;

}

System.out.println("Your issued books:");

for (IssueRecord r : s.issued.values()) {

Book b = books.get(r.bookId);

long fine = calculateFine(r.dueDate, LocalDate.now());

System.out.printf(" ID:%d | %s | Issued:%s | Due:%s | Fine(if today):%d\n",

r.bookId,

(b == null ? "(deleted book)" : b.title),

r.issueDate.format(DateTimeFormatter.ISO_DATE),

r.dueDate.format(DateTimeFormatter.ISO_DATE),

fine);

}

}

long calculateFine(LocalDate due, LocalDate today) {

if (!today.isAfter(due)) {

return 0L;

}

long days = ChronoUnit.DAYS.between(due, today);

return days * FINE_PER_DAY;

}

// ---------- Persistence ----------

public void saveToDisk() {

try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(LIBRARY_FILE))) {

oos.writeObject(this);

} catch (IOException e) {

System.out.println("Failed to save library: " + e.getMessage());

}

}

public static Library loadFromDisk() {

File f = new File(LIBRARY_FILE);

if (!f.exists()) {

System.out.println("No saved data found. Starting new library.");

return new Library();

}

try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(f))) {

Library lib = (Library) ois.readObject();

lib.scanner = new Scanner(System.in);

System.out.println("Loaded library data.");

return lib;

} catch (Exception e) {

System.out.println("Failed to load saved data: " + e.getMessage());

return new Library();

}

}