作者：敲代码の流川枫
博客主页：流川枫的博客
专栏：和我一起学java
语录：Stay hungry stay foolish
工欲善其事必先利其器，给大家介绍一款超牛的斩获大厂offer利器——牛客网
文章目录
前言
以面向对象的思想找到并且抽象出图书管理所需要的对象，再分析这些类和对象应该具有哪些属性和方法，对象通过“属性”和“方法”来分别对应事物所具有的静态属性和动态属性，最后分析类和类之间具体有什么关系，通过各个对象间的交互，使用对象、类、继承、封装、接口等基本概念完成序设计
抽象出来的对象有：书，书架，用户等，分别建立三个包管理
book
Book
package book;
public class Book {
//书名
private String name;
//作者
private String author;
//价格
private int price;
//类型
private String type;
//状态
private boolean isBorrow;
public Book(String name, String author, int price, String type) {
this.name = name;
this.author = author;
this.price = price;
this.type = type;
}
@Override
public String toString() {
return "Book{" +
"name='" + name + '\'' +
", author='" + author + '\'' +
", price=" + price +
", type='" + type + '\'' +
((isBorrow==true)?"已借出":"未借出")+
'}';
}
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 isBorrow() {
return isBorrow;
}
public void setBorrow(boolean borrow) {
isBorrow = borrow;
}
}
BookList
先存储三本书：
package book;
public class BookList {
private Book[] books = new Book[10];
private int usedSize;//存储当前书的个数
public BookList() {
books[0] = new Book("三国演义","罗贯中",90,"小说");
books[1] = new Book("红楼梦","曹雪芹",80,"小说");
books[2] = new Book("水浒传","施耐庵",70,"小说");
this.usedSize = 3;
}
public int getUsedSize() {
return usedSize;
}
public void setUsedSize(int usedSize) {
this.usedSize = usedSize;
}
public Book getPos(int pos){
return books[pos];
}
//存储一本书到指定的位置
public void setBooks(Book book,int pos){
books[pos] = book;
}
}
//将对数组的操作写到一个接口中operation
IOperation
package operation;
import book.BookList;
public interface IOperation {
void work(BookList bookList);
}
AddOperation
package operation;
import book.Book;
import book.BookList;
import java.util.Scanner;
public class AddOperation implements IOperation{
//添加图书
public void work(BookList bookList){
System.out.println("添加图书");
System.out.println("请输入书名");
Scanner scanner = new Scanner(System.in);
String name = scanner.nextLine();
System.out.println("请输入作者");
String author = scanner.nextLine();
System.out.println("请输入价格");
int price = scanner.nextInt();
//读取回车
scanner.nextLine();
System.out.println("请输入类型");
String type = scanner.nextLine();
Book book = new Book(name,author,price,type);
//获取可以存放的位置
int currentSize = bookList.getUsedSize();
//放到指定位置
bookList.setBooks(book,currentSize);
//书的个数加一
bookList.setUsedSize(currentSize+1);
}
}BorrowOperation
package operation;
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("请输入书名");
Scanner scanner = new Scanner(System.in);
String name = scanner.nextLine();
//遍历是否有要借阅的书并记录下标
int index = -1;
int currentSize = bookList.getUsedSize();
for (int i = 0; i < currentSize ; i++) {
Book book = bookList.getPos(i);
if(name.equals(book.getName())){
if(book.isBorrow()){
System.out.println("已借出");
}
else{
book.setBorrow(true);
System.out.println("借阅成功");
}
return;
}
}
System.out.println("没有要借阅的书");
}
}
DelOperation
package operation;
import book.Book;
import book.BookList;
import java.util.Scanner;
public class DelOperation implements IOperation{
public void work(BookList bookList){
System.out.println("删除图书");
System.out.println("请输入书名");
Scanner scanner = new Scanner(System.in);
String name = scanner.nextLine();
//遍历是否有要删除的书并记录下标
int index = -1;
int currentSize = bookList.getUsedSize();
for (int i = 0; i < currentSize ; i++) {
Book book = bookList.getPos(i);
if(name.equals(book.getName())){
index = i;
break;
}
}
if(index == -1){
System.out.println("没有要删除的书");
return ;
}
for (int i = index; i < currentSize-1 ; i++) {
Book book = bookList.getPos(i+1);
bookList.setBooks(book,i);
}
bookList.setBooks(null,currentSize-1);
//重置有效长度
bookList.setUsedSize(currentSize-1);
System.out.println("删除成功");
}
}
假设有四本书，那么i+1最大值就是3，即 i < currentSize-1才不会越界
删除书之后要置空，否则可能会出现内存泄漏
一个对象没有人引用才会回收
DisplayOperation
package operation;
import book.Book;
import book.BookList;
public class DisplayOperation implements IOperation{
public void work(BookList bookList){
System.out.println("显示图书");
int currentSize = bookList.getUsedSize();
for (int i = 0; i < currentSize ; i++) {
Book book = bookList.getPos(i);
System.out.println(book);
}
}
}
ExitOperation
package operation;
import book.BookList;
import com.sun.xml.internal.ws.api.model.wsdl.WSDLOutput;
public class ExitOperation implements IOperation{
public void work(BookList bookList){
System.out.println("退出系统");
System.exit(0);
}
}
FindOperation
package operation;
import book.Book;
import book.BookList;
import java.util.Scanner;
public class FindOperation implements IOperation{
//查找图书
public void work(BookList bookList){
System.out.println("查找图书");
System.out.println("请输入书名：");
Scanner scanner = new Scanner(System.in);
String name = scanner.nextLine();
int currentSize = bookList.getUsedSize();
for (int i = 0; i < currentSize ; i++) {
Book book = bookList.getPos(i);
if(name.equals(book.getName())){
System.out.println(book);
return;
}
}
System.out.println("没有这本书");
}
}
ReturnOperation
package operation;
import book.Book;
import book.BookList;
import java.util.Scanner;
public class ReturnOperation implements IOperation{
public void work(BookList bookList){
System.out.println("归还图书");
System.out.println("请输入书名");
Scanner scanner = new Scanner(System.in);
String name = scanner.nextLine();
int index = -1;
int currentSize = bookList.getUsedSize();
for (int i = 0; i < currentSize ; i++) {
Book book = bookList.getPos(i);
if(name.equals(book.getName())){
book.setBorrow(false);
System.out.println("归还成功");
return;
}
}
System.out.println("没有要归还的书");
}
}
user
User
package user;
import book.BookList;
import operation.IOperation;
public abstract class User {
protected String name;
//只是定义数组， 没有初始化，内存没有分配
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);
}
}
需要写一个操作接口数组的方法doOperation()
AdminUser
package user;
import operation.*;
import java.util.Scanner;
//管理员
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("*************");
System.out.println("hello"+name+"欢迎来到图书管理");
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("*************");
System.out.println("请输入你的操作：");
Scanner scanner = new Scanner(System.in);
int choice = scanner.nextInt();
return choice;
}
}
NormalUser
package user;
import operation.*;
import java.util.Scanner;
//普通用户
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("*************");
System.out.println("hello" + name + "欢迎来到图书管理");
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("*************");
System.out.println("请输入你的操作：");
Scanner scanner = new Scanner(System.in);
int choice = scanner.nextInt();
return choice;
}
}
Main
import book.BookList;
import user.AdminUser;
import user.NormalUser;
import user.User;
import java.util.Scanner;
public class Main {
//利用向上转型确定是哪个对象
public static User login(){
System.out.println("请输入你的姓名");
Scanner scanner = new Scanner(System.in);
String userName = scanner.nextLine();
System.out.println("请输入你的身份：1. 管理员 2. 用户");
int choice = scanner.nextInt();
if(choice==1){
return new AdminUser(userName);
}
else{
return new NormalUser(userName);
}
}
public static void main(String[] args) {
//先放三本书
BookList bookList = new BookList();
//登录
User user = login();
while(true){
int choice = user.menu();
user.doOperation(choice,bookList);
}
}
}
当引用的对象不同时，会打印不同的菜单
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