一、设计图书馆系统

Java是一个面向对象的语言，在编写代码的之前，我们要先确定有哪些对象

图书馆，首先有很多书，还有书架来放置这些书。然后是对书进行操作的人，比如普通用户和管理员。最后是对关于书的各种操作，例如：对于普通用户，借书、还书等等。对于管理员，添加书籍、查找书籍等等。

大致结构如图

 二、代码实现

1.book包

1）book

package book;

/**
 * 书籍
 */
public class Book {
    private String name;//书名
    private String auther;//作者
    private int Price;//价格
    private String type;//书籍类型
    private boolean isBorrowed;//是否被借出


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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAuther() {
        return auther;
    }

    public void setAuther(String auther) {
        this.auther = auther;
    }

    public int getPrice() {
        return Price;
    }

    public void setPrice(int price) {
        Price = price;
    }

    public String getType() {
        return type;
    }

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

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

    @Override
    public String toString() {
        return "Book{" +
                "name='" + name + '\'' +
                ", auther='" + auther + '\'' +
                ", Price=" + Price +
                ", type='" + type + '\'' +
                ((isBorrowed == true)?", 已经借出":", 未被借出")  +
               // ", num=" + num +
                '}';
    }
}

2）booklist

package book;

/**
 * 书架
 */
public class BookList {
    private Book[] books; //书架
    private int usedSize;//记录当前书架上 实际存放的数量，默认为0
    public BookList() {
        this.books = new Book[10];//初始化书架的大小
        //书架上原本有的书籍
       books[0] = new Book("三国演义","罗贯中",10,"小说");
       books[1] = new Book("西游记","吴承恩",10,"小说");
       books[2] = new Book("水浒传","曹雪芹",10,"小说");
       this.usedSize = 3;//现有书籍数量为3

    }

    public int getUsedSize() {
        return usedSize;
    }

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

    //传入下标，返回该下标的书籍信息
    public Book getBook(int pos){
        return this.books[pos];
    }

    //设置该下标为某本书
    public void setBooks(int pos,Book book){
        this.books[pos]=book;
    }

    public int getBooksNum(){
        return books.length; //获取书架容量
    }
}

2.operation包

1）AddOperation

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！");

        //判断容量是否满了
        int currentSize = bookList.getUsedSize();
        if (currentSize == bookList.getBooksNum()){
            System.out.println("书架容量已满，无法继续添加书籍！！");
            return;
        }
        //没满就继续添加书籍信息
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入书名：");
        String name = scanner.nextLine();

        System.out.println("请输入作者名：");
        String author = scanner.nextLine();

        System.out.println("请输入书籍类型：");
        String type = scanner.nextLine();

        System.out.println("请输入价格：");
        int price = scanner.nextInt();

        Book book = new Book(name,author,price,type);//实例化书籍对象

        //遍历数组，是否有这本书，提示有或无，并且增加数量
        for (int i = 0; i < currentSize; i++) {
            if (name.equals(bookList.getBook(i).getName())){
                System.out.println("已有这本书，不进行存放了！");
                return;
            }
        }
        bookList.setBooks(currentSize,book);
        bookList.setUsedSize(currentSize+1);
    }
}

2）BorrowOperation

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("借出图书！");

        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入要借的书名：");
        String name = scanner.nextLine();
        //这本书是否存在
        int currentSize = bookList.getUsedSize();
        for (int i = 0; i < currentSize; i++) {
            Book book = bookList.getBook(i);
            if(name.equals(book.getName())){
                book.setBorrowed(true);
                System.out.println("借阅成功！");
                System.out.println(book);
                return;
            }
        }
        System.out.println("该书不存在！！");

    }
}

3)  DelOperation

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！");
        //判断容量是否为0了，能不能继续删下去

        //输入书名，看看有没有这本书，有才能删
        System.out.println("请输入要删除的书名：");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.nextLine();

        //找这本书，记录下标pos
        int pos = -1;
        int currentSize = bookList.getUsedSize();
        int i = 0;
        for ( ; i < currentSize; i++) {
            Book book = bookList.getBook(i);
            if (name.equals(book.getName())){
               pos = i;
               break;
            }
        }
        if(currentSize == i){
            System.out.println("没有你要删除的书！！");
            return;
        }

       //开始删除
        int j = pos;
        for (; j < currentSize-1; j++) {
            Book book = bookList.getBook(j+1);
            bookList.setBooks(j,book);
        }
        bookList.setBooks(j,null);
        bookList.setUsedSize(currentSize-1);
    }
}

4)  ExitOperation

package operation;

import book.BookList;

public class ExitOperation implements IOperation{
    @Override
    public void work(BookList bookList) {
        System.exit(0);
        System.out.println("退出图书系统！");

    }
}

5)  FindOperation

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！");

        System.out.println("请输入要查找的书名：");
        Scanner scanner = new Scanner(System.in);
        String bookname = scanner.nextLine();
        //遍历数组
        int currentSize = bookList.getUsedSize();//当前已有书籍数量
        for (int i = 0; i < currentSize; i++) {
            Book book = bookList.getBook(i);//获取每一本书
            if (bookname.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！！");
    }
}

6)  IOperation

package operation;

import book.BookList;

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

7)  ReturnOperation

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("请输入要归还的书名：");
        String name = scanner.nextLine();
        //这本书是否存在
        int currentSize = bookList.getUsedSize();
        for (int i = 0; i < currentSize; i++) {
            Book book = bookList.getBook(i);
            if(name.equals(book.getName())){
                book.setBorrowed(false);
                System.out.println("归还成功！");
                System.out.println(book);
                return;
            }
        }
        System.out.println("该书不存在！！");
    }
}

8)  ShowOperation

package operation;

import book.BookList;

public class ShowOperation implements IOperation{
    @Override
    public void work(BookList bookList) {
        //System.out.println("打印图书！");
        int currentSize = bookList.getUsedSize();//当前已有书籍的数量
        for (int i = 0; i < currentSize; i++) {
            System.out.println(bookList.getBook(i));
        }
    }
}

3.user包

1)  AdminUser

package user;

import operation.*;

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 ShowOperation()
        };
    }

    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");
        System.out.println("******************************");

        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入操作");
        int choice = scanner.nextInt();
        return choice;
    }
}

2)  NormalUser

package user;

import operation.*;

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(),
                new ShowOperation()
        };
    }

    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");
        System.out.println("*****************************");

        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入操作");
        int choice = scanner.nextInt();
        return choice;
    }
}

3)  User

package user;

import book.BookList;
import operation.IOperation;

public abstract class User {
    protected String name;
    protected IOperation[] iOperations;
    public User(String name) {
        this.name = name;
    }
    public abstract int menu();
    public void doOperation(int choice, BookList bookList){
        iOperations[choice].work(bookList);
    }
}

4.主函数main测试运行

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("请输入您的用户名：");
        Scanner scanner = new Scanner(System.in);
        String name = scanner.nextLine(); //输入姓名

        System.out.println("请输入您的身份：1.管理员 2.普通用户");
        int choice = scanner.nextInt(); //输入数字选择身份

        if (choice == 1){
            //管理员
            return new AdminUser(name);
        }else {
            //普通用户
            return new NormalUser(name);

        }

    }
    public static void main(String[] args) {
        BookList bookList = new BookList();
        //user指向的对象 取决于 返回的值（管理员/普通用户）
        User user = login();//
        while (true){
            //choice 指向的对象 菜单返回的（操作数字）
            int choice = user.menu();
            System.out.println("操作数："+choice);
            //根据choice 的选择 来调用对应的方法

            user.doOperation(choice,bookList);
        }

    }
}

1）管理员操作效果 

2）普通用户操作效果