前言

前几篇文章讲到了Java的基本语法规则，今天我们就用前面学到的数组，类和对象，封装，继承，多态，抽象类，接口等做一个图书管理借阅系统。

1.分析图书管理系统要实现的功能

Java语言是面向对象的，所以首先要分析完成这个图书管理系统，有哪些对象：

👱使用者User

📘书Book

📲操作Operation

使用者分为两种，普通用户（NormalUser）和图书管理员（AdminUser）对于普通用户来说，需要查找，借阅，归还图书操作。

对于图书管理员来说，需要查找，新增，删除，显示图书操作。

🥇2.在IDEA中创建对象

🥇3.实现book对象

🥉Book类

书有以下属性：

书名 String name

作者 String author

价格 int price

类型 String type

是否被借出 boolean isBorrow

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

注意：这里的控制符全部设置为了私有的，需要提供方法来获取

提供get( )和set( )进行设置和获取

 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;
    }

提供一个构造方法

注意构造方法中不提供isBorrow，isBorrow是boolean类型，默认值为false，表示未被借出

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

提供ToString方法显示书的信息

  public String toString() {
        return "Book{" +
                "name='" + name + '\'' +
                ", author='" + author + '\'' +
                ", price=" + price +
                ", type='" + type + '\'' +
                ", isBorrowed=" + isBorrowed +((isBorrowed==true)?"已被借阅":"未被借阅")+
                '}';
    }

完整的book类

package book;
public class Book {
    private String name;
    private String author;
    private int price;
    private String type;
    private boolean isBorrowed;
    //构造方法
    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=" + isBorrowed +((isBorrowed==true)?"已被借阅":"未被借阅")+
                '}';
    }
}

🥉BookList类

用于存放book，相当于书架

设置一个book类型的数组存存放书

private Book[] books;
• 1

再设置一个成员变量记录书的数量

private int usedSize;
• 1

提供一个构造方法，进行一次初始化

 public BookList() {
        this.books =new Book[DEFAULT_CAPACITY];
        //初始化三本书
        this.books[0]=new Book("三国演义","罗贯中",10,"小说");
        this.books[1]=new Book("西游记","吴承恩",10,"小说");
        this.books[2]=new Book("红楼梦","曹雪芹",10,"小说");
        this.usedSize=3;
    }

再提供一个book类型的成员方法获取下标为pos的book

 public Book getBook(int pos) {
        return books[pos];
    }

再提供一个方法，给一个数组下标和book，存放到bookList中

 public void setBooks(int pos,Book book) {
        books[pos]=book;
    }

提供一个方法，获取书的数量

  public int getUsedSize() {
        return usedSize;
    }

提供一个方法，修改书的数量

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

提供一个方法，获取book数组

public Book[] getBooks() {
        return books;
    }

完整的BookList类

package book;
public class BookList {
    private Book[] books;
    private int usedSize;
    private static final int DEFAULT_CAPACITY = 10;
    public BookList() {
        this.books =new Book[DEFAULT_CAPACITY];
        //初始化三本书
        this.books[0]=new Book("三国演义","罗贯中",10,"小说");
        this.books[1]=new Book("西游记","吴承恩",10,"小说");
        this.books[2]=new Book("红楼梦","曹雪芹",10,"小说");
        this.usedSize=3;
    }
    public Book getBook(int pos) {
        return books[pos];
    }
    public void setBooks(int pos,Book book) {
        books[pos]=book;
    }
    public int getUsedSize() {
        return usedSize;
    }
    public void setUsedSize(int usedSize) {
        this.usedSize = usedSize;
    }
    public Book[] getBooks() {
        return books;
    }
}

🥇4.功能

管理员或是普通用户，对书的操作都是在BookList类的数组books中进行操作，提供一个IOperation的接口，实现对数组的操作

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

创建各种类，来实现对书的所有操作，引用IOperation接口，对方法进行重写

举个例子：

public class AddOperation implements IOperation {
    @Override
    public void work(BookList bookList) {
        System.out.println("新增图书!");
    }
}

🥇5.面向用户

普通用户和图书管理员都是用户，需要进行操作，所以我们直接创建一个User类

package user;
import book.BookList;
import operation.IOperation;
public abstract class User {
    protected String name;
    protected IOperation[] iOperation;
    public User(String name) {
        this.name = name;
    }
    public abstract int menu();
    public void doOperation(int choice, BookList bookList) {
        iOperation[choice].work(bookList);
    }
}

🥉普通用户类

package user;
import operation.*;
import java.util.Scanner;
public class NormalUser extends User{
    public NormalUser(String name) {
        super(name);
        this.iOperation=new IOperation[]{
                new ExitOperation(),
                new FindOperation(),
                new BorrowOperation(),
                new ReturnOperation()
        };
    }
    @Override
    public int menu() {
        System.out.println("**********普通用户******");
        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);
        System.out.println("请输入你的操作：");
        int choice=scanner.nextInt();
        return choice;
    }
}

🥉图书管理员

package user;
import operation.*;
import java.util.Scanner;
public class AdminUser extends User{
    public AdminUser(String name) {
        super(name);
        this.iOperation=new IOperation[]{
                new ExitOperation(),
                new FindOperation(),
                new AddOperation(),
                new DelOperation(),
                new ShowOperation(),
        };
    }
    @Override
    public int menu() {
        System.out.println("**********管理员用户*****");
        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);
        System.out.println("请输入你的操作：");
        int choice=scanner.nextInt();
        return choice;
    }
}

🥉测试类

将所有类连接起来，使类之间相互交互

package user;
import book.BookList;
import java.util.Scanner;
import operation.*;
public class Main {
    public static User login(){
        System.out.println("请输入你的名字： ");
        Scanner scanner=new Scanner(System.in);
        String name= scanner.nextLine();
        System.out.println("请输入你的身份：1.管理员   2.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();
        while(true){
            int choice= user.menu();
            System.out.println("choice: "+choice);
            user.doOperation(choice,bookList);
        }
    }
}

运行结果

🥇5.实现操作功能

🥉新增图书

package operation;
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！");
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入名字：");
        String name = scanner.nextLine();
        System.out.println("请输入作者：");
        String author = scanner.nextLine();
        System.out.println("请输入类型：");
        String type = scanner.nextLine();
        System.out.println("请输入价格：");
        int price = scanner.nextInt();
        Book book=new Book(name,author,price,type);
        int curr=bookList.getUsedSize();
        for (int i = 0; i < curr; i++) {
            Book book1=bookList.getBook(i);
            if(book1.getName().equals(name)){
                System.out.println("该书已存在，无法存放！");
            } else if (curr==bookList.getBooks().length) {
                System.out.println("已经存放满，无法再存放！");
            }else {
                bookList.setBooks(curr,book);
                bookList.setUsedSize(curr+1);
            }
        }
    }
}

🥉删除图书

package operation;
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！");
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入你要删除的书名：");
        String name=scanner.nextLine();
        int curr= bookList.getUsedSize();
        int pos=-1;
        for (int i = 0; i < curr; i++) {
            Book book1=bookList.getBook(i);
            if(book1.getName().equals(name)) {
                pos = i;
                break;
            }
        }
        if (pos==-1){
            System.out.println("没有找到书名！");
        }else {
            int j=pos;
            for ( ; j < curr-1; j++) {
                Book book=bookList.getBook(j+1);
                bookList.setBooks(j,book);
            }
            bookList.setBooks(j,null);
            bookList.setUsedSize(curr-1);
            System.out.println("删除成功！");
        }
    }
}

🥉查找图书

package operation;
import book.Book;
import book.BookList;
import java.util.Scanner;
public class FindOperation implements IOperation{
    @Override
    public void work(BookList bookList) {
        System.out.println("查找图书！");
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入你要查找的书名：");
        String name=scanner.nextLine();
        int curr= bookList.getUsedSize();
        for (int i = 0; i < curr; i++) {
            Book book=bookList.getBook(i);
            if(book.getName().equals(name)){
                System.out.println("找到你想查找的书名：");
                System.out.println(book);
                return;
            }
        }
        System.out.println("你要查找的书籍不存在");
    }
}

🥉借阅图书

package operation;
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！");
        Scanner scanner=new Scanner(System.in);
        System.out.println("请输入你要借阅的书名：");
        String name=scanner.nextLine();
        int curr=bookList.getUsedSize();
        for (int i = 0; i < curr; i++) {
            Book book = bookList.getBook(i);
            if(book.getName().equals(name)){
                book.setBorrowed(true);
                System.out.println("借阅成功！");
                System.out.println(book);
                return;
            }
        }
        System.out.println("借阅的书籍不存在！");
    }
}

🥉归还图书

package operation;
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！");
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入你要归还的书名：");
        String name= scanner.nextLine();
        int curr= bookList.getUsedSize();
        for (int i = 0; i < curr; i++) {
            Book book=bookList.getBook(i);
            if(book.getName().equals(name)){
                book.setBorrowed(false);
                System.out.println("归还成功！");
                System.out.println(book);
                return;
            }
        }
        System.out.println("未查找到你要归还的书名！");
    }
}

🥉打印图书

package operation;
import book.BookList;
public class ShowOperation implements IOperation{
    @Override
    public void work(BookList bookList) {
        System.out.println("打印图书！");
        int curr= bookList.getUsedSize();
        for (int i = 0; i < curr; i++) {
            System.out.println(bookList.getBook(i));
        }
    }
}

🥉退出系统

package operation;
import book.BookList;
public class ExitOperation implements IOperation{
    @Override
    public void work(BookList bookList) {
        System.out.println("退出图书！");
        System.out.println("退出系统！");
        System.exit(0);
    }
}

写文至此，如有不同见解或者疑惑，欢迎在评论区留言！

图书管理借阅系统【Java简易版】Java三大特征封装，继承，多态的综合运用