编写一个JAVA的图书管理系统主干程序

这里给出一个简单的图书管理系统的主干程序，你可以根据实际需求进行修改和完善：

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class BookManagementSystem {
    private List<Book> books;
    private User currentUser;
    private Scanner scanner;

    public BookManagementSystem() {
        books = new ArrayList<>();
        currentUser = null;
        scanner = new Scanner(System.in);
    }

    public void start() {
        boolean exit = false;
        while (!exit) {
            displayMenu();
            int choice = scanner.nextInt();
            switch (choice) {
                case 1:
                    register();
                    break;
                case 2:
                    login();
                    break;
                case 3:
                    addBook();
                    break;
                case 4:
                    deleteBook();
                    break;
                case 5:
                    borrowBook();
                    break;
                case 6:
                    returnBook();
                    break;
                case 7:
                    displayBooks();
                    break;
                case 8:
                    exit = true;
                    break;
                default:
                    System.out.println("Invalid choice, please try again.");
            }
        }
    }

    private void displayMenu() {
        System.out.println("Welcome to Book Management System!");
        if (currentUser == null) {
            System.out.println("1. Register");
            System.out.println("2. Login");
        } else {
            System.out.println("3. Add Book");
            System.out.println("4. Delete Book");
            System.out.println("5. Borrow Book");
            System.out.println("6. Return Book");
        }
        System.out.println("7. Display Books");
        System.out.println("8. Exit");
        System.out.print("Please enter your choice: ");
    }

    private void register() {
        System.out.print("Please enter your username: ");
        String username = scanner.next();
        System.out.print("Please enter your password: ");
        String password = scanner.next();
        currentUser = new User(username, password);
        System.out.println("Registration successful!");
    }

    private void login() {
        System.out.print("Please enter your username: ");
        String username = scanner.next();
        System.out.print("Please enter your password: ");
        String password = scanner.next();
        if (currentUser != null && currentUser.getUsername().equals(username) && currentUser.getPassword().equals(password)) {
            System.out.println("Login successful!");
        } else {
            System.out.println("Invalid username or password!");
        }
    }

    private void addBook() {
        if (currentUser == null) {
            System.out.println("Please login first!");
            return;
        }
        System.out.print("Please enter the book name: ");
        String name = scanner.next();
        System.out.print("Please enter the author name: ");
        String author = scanner.next();
        books.add(new Book(name, author));
        System.out.println("Book added successfully!");
    }

    private void deleteBook() {
        if (currentUser == null) {
            System.out.println("Please login first!");
            return;
        }
        System.out.print("Please enter the book name: ");
        String name = scanner.next();
        for (Book book : books) {
            if (book.getName().equals(name)) {
                books.remove(book);
                System.out.println("Book deleted successfully!");
                return;
            }
        }
        System.out.println("Book not found!");
    }

    private void borrowBook() {
        if (currentUser == null) {
            System.out.println("Please login first!");
            return;
        }
        System.out.print("Please enter the book name: ");
        String name = scanner.next();
        for (Book book : books) {
            if (book.getName().equals(name)) {
                if (!book.isBorrowed()) {
                    book.setBorrowed(true);
                    System.out.println("Book borrowed successfully!");
                    return;
                } else {
                    System.out.println("Book already borrowed!");
                    return;
                }
            }
        }
        System.out.println("Book not found!");
    }

    private void returnBook() {
        if (currentUser == null) {
            System.out.println("Please login first!");
            return;
        }
        System.out.print("Please enter the book name: ");
        String name = scanner.next();
        for (Book book : books) {
            if (book.getName().equals(name)) {
                if (book.isBorrowed()) {
                    book.setBorrowed(false);
                    System.out.println("Book returned successfully!");
                    return;
                } else {
                    System.out.println("Book not borrowed!");
                    return;
                }
            }
        }
        System.out.println("Book not found!");
    }

    private void displayBooks() {
        System.out.println("Book Name\tAuthor\tBorrowed");
        for (Book book : books) {
            System.out.println(book.getName() + "\t" + book.getAuthor() + "\t" + book.isBorrowed());
        }
    }

    public static void main(String[] args) {
        BookManagementSystem system = new BookManagementSystem();
        system.start();
    }
}

class User {
    private String username;
    private String password;

    public User(String username, String password) {
        this.username = username;
        this.password = password;
    }

    public String getUsername() {
        return username;
    }

    public String getPassword() {
        return password;
    }
}

class Book {
    private String name;
    private String author;
    private boolean borrowed;

    public Book(String name, String author) {
        this.name = name;
        this.author = author;
        this.borrowed = false;
    }

    public String getName() {
        return name;
    }

    public String getAuthor() {
        return author;
    }

    public boolean isBorrowed() {
        return borrowed;
    }

    public void setBorrowed(boolean borrowed) {
        this.borrowed = borrowed;
    }
}

这个程序实现了一个简单的图书管理系统，包括用户注册、登录、添加、删除、借阅、归还图书等功能。其中，User类表示用户，Book类表示图书，BookManagementSystem类为主干程序，包含各种操作图书和用户的方法。