package book_management;

//书本实体类
public class Book {
    //书名
    private String bookName;
    //作者
    private String author;
    //价格
    private double price;
    //书籍类别
    private String type;
    //借阅状态，默认为false
    private boolean isBorrowed;

    public Book(String bookName,String author,double price,String type){
        this.bookName = bookName;
        this.author = author;
        this.price = price;
        this.type = type;
    }

    //只有需要修改的属性才需要提供setter - price、type、借阅状态

    public void setPrice(double price){
        this.price = price;
    }
    public void setType(String type){
        this.type = type;
    }
    public void setBorrowed(boolean borrowed){
        isBorrowed = borrowed;
    }


    public String getBookName(){
        return bookName;
    }
    public String getAuthor(){
        return author;
    }
    public double getPrice(){
        return price;
    }
    public String getType(){
        return type;
    }
    public boolean isBorrowed(){
        return isBorrowed;
    }

    @Override
    public String toString() {
        return "Book{" +
                "bookName='" + bookName + '\'' +
                ", author='" + author + '\'' +
                ", price=" + price +
                ", type='" + type + '\'' +
                ", isBorrowed=" + isBorrowed +
                '}';
    }
}

bookList类：

package book_management;

import come.B;

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

//书架类
public class BookList {
    // books存放了所有当前书架中的书，每个Book对象就是一本书的实体
    private static List<Book> books = new ArrayList<>();
    // booksName存放了所有的书本名称 - 查询书籍等都是通过书名来操作
    private static List<String> bookName = new ArrayList<>();

    // 初始化books和booksName,默认将四大名著放入书架中
    // 使用static代码块初始化static变量
    static {
        books.add(new Book("西游记","吴承恩",99.99,"小说"));
        books.add(new Book("红楼梦","曹雪芹",108.9,"小说"));
        books.add(new Book("水浒传","施耐庵",199.89,"小说"));
        books.add(new Book("三国演义","罗贯中",145.39,"小说"));

        bookName.add("西游记");
        bookName.add("红楼梦");
        bookName.add("水浒传");
        bookName.add("三国演义");
    }

    public void displayBooks(){
        for (Book book : books){
            System.out.println(book);
        }
    }

    public boolean contains(String booksName){
        return BookList.bookName.contains(booksName);
    }

    public void add(Book book){
        books.add(book);
        bookName.add(book.getBookName());
    }
}

Main方法：

package book_management;

import java.util.Scanner;

//整个程序的入口
public class Main {
    private static Scanner scanner = new Scanner(System.in);
    public static void main (String[] args){
        User user = login();
        BookList bookList = new BookList();
        while(true){
            int choice = user.menu();
            if(choice == -1){
                System.out.println("ByeBye!");
                break;
            }
            user.doOperation(choice,bookList);
        }
    }

    private static User login() {
        System.out.println("请输入用户名：");
        String name = scanner.next();
        System.out.println("请选择您的角色，1为普通用户，0为管理员");
        int choice = scanner.nextInt();
        if (choice == 1){
            return new NormalUser(name);
        }
        return new AdminUser(name);
    }
}

?用户类：

package book_management;

//用户类 —— 抽象类
//不知道是普通用户还是管理员
public abstract class User {
    //用户名
    protected String name;
    //有权操作的方法
    protected IOperation[] operations;
    // 菜单，只有具体的子类才知道菜单长啥样~~
    public abstract int menu();

    public void doOperation(int choice,BookList bookList){
        operations[choice - 1].work(bookList);
    }
}