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前言

学习了类、抽象类、封装、继承、多态、接口等知识之后，为了更好的去理解贯彻知识，我们今天练习一个小项目—图书管理系统。

一、项目需求

图书管理系统，面向管理员和普通用户使用，对管理员的开放的功能有：添加图书，删除图书，查找图书，显示图书和退出程序等；对普通用户的开放的功能有：查找图书，借阅图书，归还图书和退出程序。

二、实现思路

首先我们想到的对象就是用户和书。

用户包括管理员和普通用户，书要有放书的书架，不同的用户有不同的操作。

接下来我们就要实现这些操作。

三、代码实现

1. book包

Book类

package book;

import java.security.SecureRandom;

public class Book {
    private String name;//书名
    private String author;//作者
    private int price;//价格
    private String type;//类型
    private boolean isBorrowed;//是否借出

    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) ?  " 已经被借出 " : "  未被借出 ")+
                '}';
    }
}

BookList类

package book;

public class BookList {
    private Book[] books = new Book[10];
    private int usedSize;
    public BookList(){
        books[0] = new Book("三国演义","罗贯中",17,"小说");
        books[1] = new Book("西游记","吴承恩",40,"小说");
        books[2] = new Book("水浒传","施耐庵",57,"小说");
        this.usedSize = 3;
    }

    public int getUsedSize() {
        return usedSize;
    }

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

    /**
     * 获取到pos位置的一本书
     * @param pos
     * @return
     */
    public Book getPos(int pos){
        return this.books[pos];
    }

    /**
     * 设置pos下标为一本书->[添加一本书]
     * @param pos
     * @param book
     */
    public void setBook(int pos,Book book){
        this.books[pos] = book;
    }
}

2. operations包

AddOperation类

package operations;

import book.Book;
import book.BookList;
import com.sun.xml.internal.ws.policy.privateutil.PolicyUtils;

import java.util.Scanner;


public class AddOperation implements IOperation {

    @Override
    public void work(BookList bookList) {
        System.out.println("新增图书");
        //输入图书信息
        System.out.println("输入新增图书名称:");
        String name = scanner.nextLine();
        System.out.println("输入新增图书作者:");
        String author = scanner.nextLine();
        System.out.println("输入新增图书价格:");
        int price = scanner.nextInt();
        scanner.nextLine();
        System.out.println("输入新增图书类型:");
        String type = scanner.nextLine();

        Book book = new Book(name, author, price, type);
        //获取存书位置
        int size = bookList.getUsedSize();
        //把书放到书架（数组）
        bookList.setBook(size,book);
        //书的总数加1
        bookList.setUsedSize(size+1);
        System.out.println("添加成功！");
    }
}

BorrowOperation类

package operations;

import book.Book;
import book.BookList;

import java.util.Scanner;

public class BorrowOperation implements IOperation{

    public void work(BookList bookList){
        System.out.println("借阅图书！");
        System.out.println("请输入你要借阅的图书的名字：");
        String name = scanner.nextLine();
        int size = bookList.getUsedSize();
        for (int i = 0; i < size; i++) {
            Book book = bookList.getPos(i);
            if(name.equals(book.getName())){
                book.setBorrowed(true);
                System.out.println("借阅成功！");
                System.out.println(book);
                return;
            }
        }
        System.out.println("没有你要借阅的这本书！");
    }

}

DelOperation类

package operations;

import book.Book;
import book.BookList;


public class DelOperation implements IOperation{

    public void work(BookList bookList){
        System.out.println("删除图书！");
        //1.根据书名找到书的位置index
        System.out.println("请输入你要删除的图书：");
        String name = scanner.nextLine();
        int currentSize = bookList.getUsedSize();
        int index = 0;//存储找到的下标
        int i = 0;
        for (; i < currentSize; i++) {
            Book book = bookList.getPos(i);
            if(book.getName().equals(name)){
                index = i;
                break;
            }
        }
        if(i >= currentSize){
            System.out.println("没有你要删除的这本书！");
            return;
        }
        //2.进行删除
        for (int j = 0; j < currentSize - 1; j++) {
            Book book = bookList.getPos(j + 1);
            bookList.setBook(j,book);
        }
        bookList.setBook(currentSize,null);
        bookList.setUsedSize(currentSize-1);
        System.out.println("删除成功! ");
    }
}

DisplayOperation类

package operations;

import book.Book;
import book.BookList;


public class DisplayOperation implements IOperation{

    public void work(BookList bookList){
        System.out.println("打印图书！");
        int size = bookList.getUsedSize();
        for (int i = 0; i < size; i++) {
            Book book = bookList.getPos(i);
            System.out.println(book);
        }
    }
}

ExitOperation类

package operations;

import book.BookList;


public class ExitOperation implements IOperation{

    public void work(BookList bookList){
        System.out.println("退出系统！");
        System.exit(0);
    }
}

FindOperation类

package operations;

import book.Book;
import book.BookList;


public class FindOperation implements IOperation{

    public void work(BookList bookList){
        System.out.println("查找图书！");
        String name = scanner.nextLine();
        int size = bookList.getUsedSize();
        for (int i = 0; i < size; i++) {
            Book book = bookList.getPos(i);
            if(name.equals(book.getName())){
                System.out.println("找到了这本书，信息如下：");
                System.out.println(book);
                return;
            }
        }
        System.out.println("没有找到这本书!");
    }
}

ReturnOperation类

package operations;

import book.Book;
import book.BookList;


public class ReturnOperation implements IOperation{

    public void work(BookList bookList){
        System.out.println("归还图书！");
        System.out.println("请输入你要归还的图书的名字：");
        String name = scanner.nextLine();
        int size = bookList.getUsedSize();
        for (int i = 0; i < size; i++) {
            Book book = bookList.getPos(i);
            if(name.equals(book.getName())){
                book.setBorrowed(false);
                System.out.println("归还成功！");
                System.out.println(book);
                return;
            }
        }
        System.out.println("没有你要归还的这本书！");
    }

}

IOperation接口

package operations;

import book.BookList;

import java.util.Scanner;

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

3. user包

AdminUser类

package user;

import com.sun.xml.internal.ws.policy.privateutil.PolicyUtils;
import operations.*;

import java.util.Scanner;
import java.util.SplittableRandom;


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("============管理员菜单============");
        System.out.println("hello" +" " + this.name + " 欢迎来到这里");
        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.退出系统");
        System.out.println("=================================");

        Scanner scanner = new Scanner(System.in);
        int choice = scanner.nextInt();
        return choice;
    }
}

NormalUser类

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("============普通用户菜单============");
        System.out.println("hello" +" " + this.name + " 欢迎来到这里");
        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.退出系统");
        System.out.println("=================================");

        Scanner scanner = new Scanner(System.in);
        int choice = scanner.nextInt();
        return choice;
    }
}

User类

package user;

import book.BookList;
import operations.IOperation;


public abstract class User {
    protected String name;

    protected IOperation[] iOperations;

    public User(String name){
        this.name = name;
    }

    public abstract int menu();

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

Main类

import book.BookList;
import user.AdminUser;
import user.NormalUser;
import user.User;

import java.util.Scanner;

public class Main {

    public static User login(){
        System.out.println("请输入你的姓名：");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.nextLine();
        System.out.println("请输入你的身份：1->管理员。0->普通用户");
        int choice = scanner.nextInt();
        if(choice == 1){
            return new AdminUser(name);
        }else {
            return new NormalUser(name);
        }
    }

    public static void main(String[] args) {
        BookList bookList = new BookList();
        User user = login();//向上转型
        while(true) {
            int choice = user.menu();//发生了动态绑定 -> 多态
            //根据你的choice 调用合适的操作
            user.doWork(choice, bookList);
        }
    }
}

四、效果展示