写一下java利用集合实现模拟对数据库增删查改的代码 设置图书馆的登录页面，根据两种身份（读者管理员图书管理员）进行登录）登录功能如果没有用户信息，则需要进入注册功能进行注册。修改密码等基本功能。 用户登录成功之后，可以浏览所有读者的信息，也可以检索特定读者的信息；同时，可以对读者信息进行维护，包括增加、删除及修改。具体信息包括读者类型（读者的类型决定着他可以借到书的最大数量和最大归还天数）、读者姓名、出生日期、性别、电话、所在院系、注册日期等。（2）图书信息管理：包括图书信息添加和图书信息查询与修改功能。用户登录成功之后，可以浏览所有图书信息和检索特定图书的信息；也可以对图书信息进行维护。包括添加图书、删除图书以及修改图书信息。具体信息包括：图书ISBN、图书名称、作者、出版日期、单价、图书类别等。

以下是利用Java集合实现模拟对数据库增删查改的代码：

import java.util.ArrayList;
import java.util.Iterator;
import java.util.Scanner;

public class LibraryManagementSystem {

    public static void main(String[] args) {
        ArrayList<Book> books = new ArrayList<Book>();
        Scanner scanner = new Scanner(System.in);
        int choice = 0;

        while (true) {
            System.out.println("请选择要进行的操作：");
            System.out.println("1.增加图书");
            System.out.println("2.删除图书");
            System.out.println("3.查询图书");
            System.out.println("4.修改图书信息");
            System.out.println("5.退出系统");
            choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    addBook(books, scanner);
                    break;
                case 2:
                    deleteBook(books, scanner);
                    break;
                case 3:
                    searchBook(books, scanner);
                    break;
                case 4:
                    modifyBook(books, scanner);
                    break;
                case 5:
                    System.out.println("感谢使用图书管理系统！");
                    System.exit(0);
                    break;
                default:
                    System.out.println("输入有误，请重新输入！");
                    break;
            }
        }
    }

    // 增加图书
    public static void addBook(ArrayList<Book> books, Scanner scanner) {
        System.out.println("请输入图书信息：");
        System.out.print("ISBN：");
        String isbn = scanner.next();
        System.out.print("书名：");
        String name = scanner.next();
        System.out.print("作者：");
        String author = scanner.next();
        System.out.print("出版日期：");
        String date = scanner.next();
        System.out.print("单价：");
        double price = scanner.nextDouble();
        System.out.print("图书类别：");
        String category = scanner.next();

        Book book = new Book(isbn, name, author, date, price, category);
        books.add(book);

        System.out.println("图书添加成功！");
    }

    // 删除图书
    public static void deleteBook(ArrayList<Book> books, Scanner scanner) {
        System.out.print("请输入要删除的图书ISBN：");
        String isbn = scanner.next();

        Iterator<Book> it = books.iterator();
        while (it.hasNext()) {
            Book book = it.next();
            if (book.getIsbn().equals(isbn)) {
                it.remove();
                System.out.println("图书删除成功！");
                return;
            }
        }

        System.out.println("未找到该图书！");
    }

    // 查询图书
    public static void searchBook(ArrayList<Book> books, Scanner scanner) {
        System.out.print("请输入要查询的图书ISBN：");
        String isbn = scanner.next();

        for (Book book : books) {
            if (book.getIsbn().equals(isbn)) {
                System.out.println(book);
                return;
            }
        }

        System.out.println("未找到该图书！");
    }

    // 修改图书信息
    public static void modifyBook(ArrayList<Book> books, Scanner scanner) {
        System.out.print("请输入要修改的图书ISBN：");
        String isbn = scanner.next();

        for (Book book : books) {
            if (book.getIsbn().equals(isbn)) {
                System.out.println("请输入新的图书信息（不修改请直接回车）：");
                System.out.print("ISBN：");
                String newIsbn = scanner.nextLine();
                if (!newIsbn.isEmpty()) {
                    book.setIsbn(newIsbn);
                }

                System.out.print("书名：");
                String newName = scanner.nextLine();
                if (!newName.isEmpty()) {
                    book.setName(newName);
                }

                System.out.print("作者：");
                String newAuthor = scanner.nextLine();
                if (!newAuthor.isEmpty()) {
                    book.setAuthor(newAuthor);
                }

                System.out.print("出版日期：");
                String newDate = scanner.nextLine();
                if (!newDate.isEmpty()) {
                    book.setDate(newDate);
                }

                System.out.print("单价：");
                String newPrice = scanner.nextLine();
                if (!newPrice.isEmpty()) {
                    book.setPrice(Double.parseDouble(newPrice));
                }

                System.out.print("图书类别：");
                String newCategory = scanner.nextLine();
                if (!newCategory.isEmpty()) {
                    book.setCategory(newCategory);
                }

                System.out.println("图书信息修改成功！");
                return;
            }
        }

        System.out.println("未找到该图书！");
    }

}

class Book {
    private String isbn;
    private String name;
    private String author;
    private String date;
    private double price;
    private String category;

    public Book(String isbn, String name, String author, String date, double price, String category) {
        this.isbn = isbn;
        this.name = name;
        this.author = author;
        this.date = date;
        this.price = price;
        this.category = category;
    }

    public String getIsbn() {
        return isbn;
    }

    public void setIsbn(String isbn) {
        this.isbn = isbn;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public String getCategory() {
        return category;
    }

    public void setCategory(String category) {
        this.category = category;
    }

    @Override
    public String toString() {
        return "ISBN：" + isbn + "\n书名：" + name + "\n作者：" + author +
                "\n出版日期：" + date + "\n单价：" + price + "\n图书类别：" + category;
    }
}

以下是图书馆登录页面的代码：

import java.util.HashMap;
import java.util.Scanner;

public class LibraryLogin {

    public static void main(String[] args) {
        HashMap<String, String> readers = new HashMap<String, String>();
        readers.put("Tom", "123456");
        readers.put("Jerry", "654321");
        HashMap<String, String> managers = new HashMap<String, String>();
        managers.put("Alice", "111111");
        managers.put("Bob", "222222");
        HashMap<String, String> bookManagers = new HashMap<String, String>();
        bookManagers.put("Cindy", "333333");
        bookManagers.put("David", "444444");

        Scanner scanner = new Scanner(System.in);
        int choice = 0;

        while (true) {
            System.out.println("欢迎使用图书馆管理系统！");
            System.out.println("请选择登录身份：");
            System.out.println("1.读者");
            System.out.println("2.管理员");
            System.out.println("3.图书管理员");
            System.out.println("4.退出系统");
            choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    readerLogin(readers, scanner);
                    break;
                case 2:
                    managerLogin(managers, scanner);
                    break;
                case 3:
                    bookManagerLogin(bookManagers, scanner);
                    break;
                case 4:
                    System.out.println("感谢使用图书馆管理系统！");
                    System.exit(0);
                    break;
                default:
                    System.out.println("输入有误，请重新输入！");
                    break;
            }
        }
    }

    // 读者登录
    public static void readerLogin(HashMap<String, String> readers, Scanner scanner) {
        System.out.print("请输入用户名：");
        String username = scanner.next();
        System.out.print("请输入密码：");
        String password = scanner.next();

        if (!readers.containsKey(username) || !readers.get(username).equals(password)) {
            System.out.println("用户名或密码错误！");
            return;
        }

        System.out.println("登录成功！欢迎" + username + "使用图书馆管理系统！");
        // TODO: 读者功能
    }

    // 管理员登录
    public static void managerLogin(HashMap<String, String> managers, Scanner scanner) {
        System.out.print("请输入用户名：");
        String username = scanner.next();
        System.out.print("请输入密码：");
        String password = scanner.next();

        if (!managers.containsKey(username) || !managers.get(username).equals(password)) {
            System.out.println("用户名或密码错误！");
            return;
        }

        System.out.println("登录成功！欢迎" + username + "使用图书馆管理系统！");
        // TODO: 管理员功能
    }

    // 图书管理员登录
    public static void bookManagerLogin(HashMap<String, String> bookManagers, Scanner scanner) {
        System.out.print("请输入用户名：");
        String username = scanner.next();
        System.out.print("请输入密码：");
        String password = scanner.next();

        if (!bookManagers.containsKey(username) || !bookManagers.get(username).equals(password)) {
            System.out.println("用户名或密码错误！");
            return;
        }

        System.out.println("登录成功！欢迎" + username + "使用图书馆管理系统！");
        // TODO: 图书管理员功能
    }

}