Using Java to realize library management system (class, abstract class, encapsulation, inheritance, polymorphism, interface, sequence table)

The main content of our implementation is the addition, deletion, modification and query of books, which is divided into administrator users and ordinary users.
The flow chart is as follows:

Create book related classes

Since the operation is object-oriented, we can divide it into several pieces and operate them separately
Create a book bag with book related things in it
Create a Book class to put things related to books. Create a Book class to represent a book
Create a BookList class to save N books

Book class

public class Book {

    private String name; //The name of the book
    private String author;//author
    private int price;//Price
    private String type;//type
    private boolean isBorrowed;//Is it lent
}

Next is encapsulation

public class Book {

    private String name;
    private String author;
    private int price;
    private String type;
    private boolean isBorrowed;

    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) ? " Has been lent out" : " Not lent")+
                '}';
    }
}

Shortcut keys: right click, and then

BookList class

public class BookList {

    private Book[] books = new Book[10]; //An array of books
    private int usedSize;//How many books are there

    public BookList(){  //Put some initial values
        books[0] = new Book("Romance of the Three Kingdoms","Luo Guanzhong",17,"novel");
        books[1] = new Book("Journey to the West","Wu Chengen",47,"novel");
        books[2] = new Book("Water Margin","Shi Naian",37,"novel");
        books[3] = new Book("The Dream of Red Mansion","Cao Xueqin",35,"novel");
        this.usedSize = 4;
    }

    public int getUsedSize() {
        return usedSize;
    }

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

    public Book getPos(int pos){  //Get a book with pos location
        if(pos < 0 || pos >getUsedSize()){
            System.out.println("Illegal location!");
            return null;
        }
        return books[pos];
    }

    public void setBooks(int pos,Book book){  //Set the pos subscript to a book
        if(pos < 0 || pos > getUsedSize()){
            return;
        }
        books[pos] = book;
    }
}

Create operation related classes

First, create a package operation, which contains classes for related operations
Here, I show the content of each operation to be realized first, so as to feel it more intuitively.

IOperation interface

The purpose of using the interface is that this method is used for subsequent additions, deletions, queries and changes. It is helpful for subsequent administrators and ordinary users to call it separately.

public interface IOperation {
    Scanner scanner = new Scanner(System.in);
    public void work(BookList bookList);
}