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;}@Overridepublic 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类型的数组存放书

 private Book[] books;

再设置一个成员变量记录书的数量

   private int usedSize;

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 {@Overridepublic 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()};}@Overridepublic 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(),};}@Overridepublic 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{@Overridepublic 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{@Overridepublic 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{@Overridepublic 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{@Overridepublic 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 {@Overridepublic 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{@Overridepublic 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{@Overridepublic 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！