How to implement a library management system using Java code

1. Function introduction

This library management system uses the IDEA development tool to realize

There are two identities for access to the library system:

1. Administrator identity:

2. Ordinary user identity:

us There are three packages in total, namely book, operations, and user implementation.

## 2. Main package

main function Mainly carry out the general process, initialization of the library, login to the library management system, and selection of specific operations, that is, implementation.

import book.BookList;
import user.AdminUser;
import user.NormalUser;
import user.User;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        //1.先初始化图书库，以及初始化:
        BookList bookList = new BookList();

        //2.登录
        User user = login();//向上转型，User接受管理员或者用户对象

        //3.打印菜单,进行具体操作
        while(true) {
            int choice = user.menu();
            user.doOperation(choice,bookList);
        }
    }
}

Login function:

 public static User login() {
        System.out.println("请输入你的姓名: ");
        Scanner scanner = new Scanner(System.in);
        String userName = scanner.nextLine();
        System.out.println("请输入你的身份: 1-> 管理员 2-> 用户");
        int choice = scanner.nextInt();
        if(choice == 1) {
            return new AdminUser(userName);
        }else {
            return new NormalUser(userName);
        }
    }

3. User package

Because there are two systems, administrators and ordinary users, we extract the common attributes into a User abstract class to achieve code reuse

1. User

package user;

import book.BookList;
import operations.IOperation;

public abstract class User {
    protected String name;

    IOperation[] iOperations;
    public User(String name) {
        this.name = name;
    }

    public abstract int menu();

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

2. AdminUser

package user;

import operations.*;

import java.util.Scanner;
public class AdminUser extends User{

    public AdminUser(String name) {
        super(name);
        this.iOperations = new IOperation[]{
                new ExitOperation(),
                new FindOperation(),
                new AddOperation(),
                new DelOperation(),
                new DisplayOperation()
        };
    }
    public int menu() {
        System.out.println("欢迎: "+name+"来到图书馆");
        System.out.println("**********************************");
        System.out.println("1. 查找图书");
        System.out.println("2. 新增图书");
        System.out.println("3. 删除图书");
        System.out.println("4. 显示图书");
        System.out.println("0. 退出图书");
        System.out.println("**********************************");
        System.out.println("请输入你的操作: ");
        Scanner scanner = new Scanner(System.in);
        int choice = scanner.nextInt();
        return choice;
    }
}

3. NormalUser

package user;

import operations.*;

import java.util.Scanner;
public class NormalUser extends User{

    public NormalUser(String name) {
        super(name);
        this.iOperations = new IOperation[]{
                new ExitOperation(),
                new FindOperation(),
                new BorrowOperation(),
                new ReturnOperation()
        };
    }

    public int menu() {
        System.out.println("欢迎: "+name+"来到图书馆");
        System.out.println("**********************************");
        System.out.println("1. 查找图书");
        System.out.println("2. 借阅图书");
        System.out.println("3. 归还图书");
        System.out.println("0. 退出图书");
        System.out.println("**********************************");
        System.out.println("请输入你的操作: ");
        Scanner scanner = new Scanner(System.in);
        int choice = scanner.nextInt();
        return choice;
    }
}

4. Book package

We write the attributes of the book, and in the BookList type Initialize the books in the library.

1. Book

package book;
public class Book {
    private String name;//书名
    private String author;//作者
    private int price;//价格
    private String type;//书的类型
    private boolean isBorrowed;//书默认未借出

    public Book(String name, String author, int price, String type) {
        this.name = name;
        this.author = author;
        this.price = price;
        this.type = type;
    }

    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 int getPrice() {
        return price;
    }

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

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public boolean isBorrowed() {
        return isBorrowed;
    }

    public void setBorrowed(boolean borrowed) {
        isBorrowed = borrowed;
    }

    @Override
    public String toString() {
        return "Book{" +
                "name='" + name + '\'' +
                ", author='" + author + '\'' +
                ", price=" + price +
                ", type='" + type + '\'' +
                ","+ ((isBorrowed == true) ? "该书已借出" : "该书未借出" )+
                '}';
    }
}

2. BookList

package book;
public class BookList {
    public Book[] books = new Book[100];
    public int usedSize;//用来存当前共有多少本书


    /**
     * 事先通过代码块
     *
     * 事先存进去三本书
     */
    {
        books[0] = new Book("java","高斯林",95,"IT");
        books[1] = new Book("C++","姚琳",93,"IT");
        books[2] = new Book("python","马瑟斯",80,"IT");
        this.usedSize = 3;
    }

    public Book getPos(int pos) {
        //获取某一位置的书
        return books[pos];
    }

    public void setBooks(Book book,int pos) {
        //存储一本书 到指定位置
        books[pos] = book;

    }
    public int getUsedSize() {
        return usedSize;
    }

    public void setUsedSize(int usedSize) {
        this.usedSize = usedSize;
    }
}

5. Operations package

Our book management system has For many specific operations, in order to facilitate polymorphism and error checking later, we implement a specific IOperation interface, and each specific operation implements this interface.

1. IOperation interface

package operations;

import book.BookList;

public interface IOperation {
    void work(BookList bookList);
}

2. AddOperation

Add books:

package operations;

import book.Book;
import book.BookList;

import java.util.Scanner;
public class AddOperation implements IOperation{
    @Override
    public void work(BookList bookList) {
        System.out.println("新增图书! ");
        System.out.println("请输入要新增的图书的名字: ");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.nextLine();
        System.out.println("请输入要新增的图书的作者: ");
        String author = scanner.nextLine();
        System.out.println("请输入要新增的图书的价格: ");
        int price = scanner.nextInt();
        System.out.println("请输入要新增的图书的类型: ");
        String type = scanner.nextLine();

        Book book = new Book(name,author,price,type);

        //1.获取当前书存放的位置
        int curSize = bookList.getUsedSize();
        //2.把书放在指定位置
        bookList.setBooks(book,curSize);
        //3.更新书的个数
        bookList.setUsedSize(curSize+1);

    }
}

3. BorrowOperation

Borrow books:

package operations;

import book.Book;
import book.BookList;

import java.util.Scanner;

public class BorrowOperation implements IOperation{
    @Override
    public void work(BookList bookList) {
        System.out.println("借阅图书! ");
        System.out.println("请输入要借阅的图书的名字: ");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.nextLine();
        for (int i = 0; i < bookList.getUsedSize(); i++) {
            Book book = bookList.getPos(i);
            if(name.equals(book.getName())) {
                if(book.isBorrowed()) {
                    System.out.println("该书已经被借出! ");
                }else {
                    book.setBorrowed(true);
                    System.out.println("借阅图书成功! ");
                    return;
                }
            }
        }
        System.out.println("没有你要借阅的书! ");
    }
}

4. DelOperation

Delete books :

package operations;

import book.Book;
import book.BookList;

import java.util.Scanner;
public class DelOperation implements IOperation{
    @Override
    public void work(BookList bookList) {
        System.out.println("删除图书! ");
        System.out.println("请输入要删除的图书: ");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.nextLine();

        //查找图书是否有此图书，记录下标
        int index = -1;
        for (int i = 0; i < bookList.getUsedSize(); i++) {
            Book book = bookList.getPos(i);
            if(name.equals(book.getName())) {
               index = i;
               break;
            }
        }
        if(index == -1) {
            System.out.println("没有 "+name+"这本书!");
            return;
        }
        for (int i = index; i < bookList.getUsedSize()-1; i++) {
            Book book = bookList.getPos(i+1);
            bookList.setBooks(book,i);
        }

        //删除的书,要置空
        bookList.setBooks(null, bookList.getUsedSize()-1);
        bookList.setUsedSize(bookList.getUsedSize()-1);
    }
}

5. DisplayOperation

Display books:

package operations;

import book.Book;
import book.BookList;
public class DisplayOperation implements IOperation{
    @Override
    public void work(BookList bookList) {
        System.out.println("显示图书! ");
        for (int i = 0; i < bookList.getUsedSize(); i++) {
            Book book = bookList.getPos(i);
            System.out.println(book);
        }
    }
}

6. ExitOperation

Exit books:

package operations;

import book.BookList;
public class ExitOperation implements IOperation{
    @Override
    public void work(BookList bookList) {

        System.out.println("退出系统! ");
        System.exit(0);
    }
}

7. FindOperation

Find books:

package operations;

import book.Book;
import book.BookList;

import java.util.Scanner;

public class FindOperation implements IOperation{
    @Override
    public void work(BookList bookList) {

        //查找图书
        System.out.println("查找图书! ");
        System.out.println("请输入要查找的图书: ");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.nextLine();
        for (int i = 0; i < bookList.getUsedSize(); i++) {
            Book book = bookList.getPos(i);
            if(name.equals(book.getName())) {
                System.out.println("找到了! ");
                System.out.println(book);
                return;
            }
        }
        System.out.println("没有这本书! ");
    }
}

8. ReturnOperation

Return books:

package operations;

import book.Book;
import book.BookList;

import java.util.Scanner;
public class ReturnOperation implements IOperation{
    @Override
    public void work(BookList bookList) {
        System.out.println("归还图书! ");
        System.out.println("请输入要归还的图书的名字: ");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.nextLine();
        for (int i = 0; i < bookList.getUsedSize(); i++) {
            Book book = bookList.getPos(i);
            if(name.equals(book.getName())) {
                book.setBorrowed(false);
                System.out.println("归还图书成功! ");
                return;
            }
        }
        System.out.println("没有你要归还的书! ");
    }
}

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