设计一个在线图书阅读器系统（面向对象设计）。
被问到：亚马逊、微软，以及更多采访
解决方案：假设我们要设计一个基本的在线阅读系统，它提供以下功能：
• 搜索图书数据库并阅读一本书。
• 用户成员资格创建和扩展。
• 一次只有一个活跃用户，并且该用户只有一本活跃的图书
类 OnlineReaderSystem 代表我们程序的主体。我们可以实施
存储有关所有书籍的信息的类处理用户管理并刷新显示，但这会使这个类变得相当庞大。相反，我们选择将这些组件拆分为 Library、UserManager 和 Display 类。
课程：
1. 用户
2. 预订
3. 图书馆
4. 用户管理器
5. 显示
6. 在线阅读系统
完整代码如下：
Java
import java.util.HashMap;
/*
* This class represents the system
*/
class OnlineReaderSystem {
private Library library;
private UserManager userManager;
private Display display;
private Book activeBook;
private User activeUser;
public OnlineReaderSystem()
{
userManager = new UserManager();
library = new Library();
display = new Display();
}
public Library getLibrary()
{
return library;
}
public UserManager getUserManager()
{
return userManager;
}
public Display getDisplay()
{
return display;
}
public Book getActiveBook()
{
return activeBook;
}
public void setActiveBook(Book book)
{
activeBook = book;
display.displayBook(book);
}
public User getActiveUser()
{
return activeUser;
}
public void setActiveUser(User user)
{
activeUser = user;
display.displayUser(user);
}
}
/*
* We then implement separate classes to handle the user
* manager, the library, and the display components
*/
/*
* This class represents the Library which is responsible
* for storing and searching the books.
*/
class Library {
private HashMap books;
public Library()
{
books = new HashMap();
}
public Boolean addBook(int id, String details, String title)
{
if (books.containsKey(id)) {
return false;
}
Book book = new Book(id, details, title);
books.put(id, book);
return true;
}
public Boolean addBook(Book book)
{
if (books.containsKey(book.getId())) {
return false;
}
books.put(book.getId(), book);
return true;
}
public boolean remove(Book b)
{
return remove(b.getId());
}
public boolean remove(int id)
{
if (!books.containsKey(id)) {
return false;
}
books.remove(id);
return true;
}
public Book find(int id)
{
return books.get(id);
}
}
/*
* This class represents the UserManager which is responsible
* for managing the users, their membership etc.
*/
class UserManager {
private HashMap users;
public UserManager()
{
users = new HashMap();
}
public Boolean addUser(int id, String details, String name)
{
if (users.containsKey(id)) {
return false;
}
User user = new User(id, details, name);
users.put(id, user);
return true;
}
public Boolean addUser(User user)
{
if (users.containsKey(user.getId())) {
return false;
}
users.put(user.getId(), user);
return true;
}
public boolean remove(User u)
{
return remove(u.getId());
}
public boolean remove(int id)
{
if (users.containsKey(id)) {
return false;
}
users.remove(id);
return true;
}
public User find(int id)
{
return users.get(id);
}
}
/*
* This class represents the Display, which is responsible
* for displaying the book, it's pages and contents. It also
* shows the current user. * It provides the method
* turnPageForward, turnPageBackward, refreshPage etc.
*/
class Display {
private Book activeBook;
private User activeUser;
private int pageNumber = 0;
public void displayUser(User user)
{
activeUser = user;
refreshUsername();
}
public void displayBook(Book book)
{
pageNumber = 0;
activeBook = book;
refreshTitle();
refreshDetails();
refreshPage();
}
public void turnPageForward()
{
pageNumber++;
System.out.println("Turning forward to page no " +
pageNumber + " of book having title " +
activeBook.getTitle());
refreshPage();
}
public void turnPageBackward()
{
pageNumber--;
System.out.println("Turning backward to page no " +
pageNumber + " of book having title " +
activeBook.getTitle());
refreshPage();
}
public void refreshUsername()
{
/* updates username display */
System.out.println("User name " + activeUser.getName() +
" is refreshed");
}
public void refreshTitle()
{
/* updates title display */
System.out.println("Title of the book " +
activeBook.getTitle() + " refreshed");
}
public void refreshDetails()
{
/* updates details display */
System.out.println("Details of the book " +
activeBook.getTitle() + " refreshed");
}
public void refreshPage()
{
/* updated page display */
System.out.println("Page no " + pageNumber + " refreshed");
}
}
/*
* The classes for User and Book simply hold data and
* provide little functionality.
* This class represents the Book which is a simple POJO
*/
class Book {
private int bookId;
private String details;
private String title;
public Book(int id, String details, String title)
{
bookId = id;
this.details = details;
this.title = title;
}
public int getId()
{
return bookId;
}
public void setId(int id)
{
bookId = id;
}
public String getDetails()
{
return details;
}
public void setDetails(String details)
{
this.details = details;
}
public String getTitle()
{
return title;
}
public void setTitle(String title)
{
this.title = title;
}
}
/*
* This class represents the User which is a simple POJO
*/
class User {
private int userId;
private String name;
private String details;
public void renewMembership()
{
}
public User(int id, String details, String name)
{
this.userId = id;
this.details = details;
this.name = name;
}
public int getId()
{
return userId;
}
public void setId(int id)
{
userId = id;
}
public String getDetails()
{
return details;
}
public void setDetails(String details)
{
this.details = details;
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
}
// This class is used to test the Application
public class AppTest {
public static void main(String[] args)
{
OnlineReaderSystem onlineReaderSystem = new OnlineReaderSystem();
Book dsBook = new Book(1, "It contains Data Structures", "Ds");
Book algoBook = new Book(2, "It contains Algorithms", "Algo");
onlineReaderSystem.getLibrary().addBook(dsBook);
onlineReaderSystem.getLibrary().addBook(algoBook);
User user1 = new User(1, " ", "Ram");
User user2 = new User(2, " ", "Gopal");
onlineReaderSystem.getUserManager().addUser(user1);
onlineReaderSystem.getUserManager().addUser(user2);
onlineReaderSystem.setActiveBook(algoBook);
onlineReaderSystem.setActiveUser(user1);
onlineReaderSystem.getDisplay().turnPageForward();
onlineReaderSystem.getDisplay().turnPageForward();
onlineReaderSystem.getDisplay().turnPageBackward();
}
} C#
using System;
using System.Collections.Generic;
/*
* This class represents the system
*/
class OnlineReaderSystem
{
private Library library;
private UserManager userManager;
private Display display;
private Book activeBook;
private User activeUser;
public OnlineReaderSystem()
{
userManager = new UserManager();
library = new Library();
display = new Display();
}
public Library getLibrary()
{
return library;
}
public UserManager getUserManager()
{
return userManager;
}
public Display getDisplay()
{
return display;
}
public Book getActiveBook()
{
return activeBook;
}
public void setActiveBook(Book book)
{
activeBook = book;
display.displayBook(book);
}
public User getActiveUser()
{
return activeUser;
}
public void setActiveUser(User user)
{
activeUser = user;
display.displayUser(user);
}
}
/*
* We then implement separate classes to handle the user
* manager, the library, and the display components
*/
/*
* This class represents the Library which is responsible
* for storing and searching the books.
*/
class Library
{
private Dictionary books;
public Library()
{
books = new Dictionary();
}
public Boolean addBook(int id, String details,
String title)
{
if (books.ContainsKey(id))
{
return false;
}
Book book = new Book(id, details, title);
books.Add(id, book);
return true;
}
public Boolean addBook(Book book)
{
if (books.ContainsKey(book.getId()))
{
return false;
}
books.Add(book.getId(), book);
return true;
}
public bool remove(Book b)
{
return remove(b.getId());
}
public bool remove(int id)
{
if (!books.ContainsKey(id))
{
return false;
}
books.Remove(id);
return true;
}
public Book find(int id)
{
return books[id];
}
}
/*
* This class represents the UserManager
* which is responsible for managing the users,
* their membership etc.
*/
class UserManager
{
private Dictionary users;
public UserManager()
{
users = new Dictionary();
}
public Boolean addUser(int id, String details,
String name)
{
if (users.ContainsKey(id))
{
return false;
}
User user = new User(id, details, name);
users.Add(id, user);
return true;
}
public Boolean addUser(User user)
{
if (users.ContainsKey(user.getId()))
{
return false;
}
users.Add(user.getId(), user);
return true;
}
public bool remove(User u)
{
return remove(u.getId());
}
public bool remove(int id)
{
if (users.ContainsKey(id))
{
return false;
}
users.Remove(id);
return true;
}
public User find(int id)
{
return users[id];
}
}
/*
* This class represents the Display, which is responsible
* for displaying the book, it's pages and contents.
* It also shows the current user. * It provides the method
* turnPageForward, turnPageBackward, refreshPage etc.
*/
class Display
{
private Book activeBook;
private User activeUser;
private int pageNumber = 0;
public void displayUser(User user)
{
activeUser = user;
refreshUsername();
}
public void displayBook(Book book)
{
pageNumber = 0;
activeBook = book;
refreshTitle();
refreshDetails();
refreshPage();
}
public void turnPageForward()
{
pageNumber++;
Console.WriteLine("Turning forward to page no " +
pageNumber + " of book having title " +
activeBook.getTitle());
refreshPage();
}
public void turnPageBackward()
{
pageNumber--;
Console.WriteLine("Turning backward to page no " +
pageNumber + " of book having title " +
activeBook.getTitle());
refreshPage();
}
public void refreshUsername()
{
/* updates username display */
Console.WriteLine("User name " +
activeUser.getName() +
" is refreshed");
}
public void refreshTitle()
{
/* updates title display */
Console.WriteLine("Title of the book " +
activeBook.getTitle() +
" refreshed");
}
public void refreshDetails()
{
/* updates details display */
Console.WriteLine("Details of the book " +
activeBook.getTitle() +
" refreshed");
}
public void refreshPage()
{
/* updated page display */
Console.WriteLine("Page no " + pageNumber +
" refreshed");
}
}
/*
* The classes for User and Book simply hold data
* and provide little functionality.
* This class represents the Book which is
* a simple POJO
*/
class Book
{
private int bookId;
private String details;
private String title;
public Book(int id, String details,
String title)
{
bookId = id;
this.details = details;
this.title = title;
}
public int getId()
{
return bookId;
}
public void setId(int id)
{
bookId = id;
}
public String getDetails()
{
return details;
}
public void setDetails(String details)
{
this.details = details;
}
public String getTitle()
{
return title;
}
public void setTitle(String title)
{
this.title = title;
}
}
/*
* This class represents the User
* which is a simple POJO
*/
class User
{
private int userId;
private String name;
private String details;
public void renewMembership()
{
}
public User(int id, String details,
String name)
{
this.userId = id;
this.details = details;
this.name = name;
}
public int getId()
{
return userId;
}
public void setId(int id)
{
userId = id;
}
public String getDetails()
{
return details;
}
public void setDetails(String details)
{
this.details = details;
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
}
// This class is used to test the Application
public class AppTest
{
public static void Main(String[] args)
{
OnlineReaderSystem
onlineReaderSystem = new OnlineReaderSystem();
Book dsBook = new Book(1, "It contains Data Structures", "Ds");
Book algoBook = new Book(2, "It contains Algorithms", "Algo");
onlineReaderSystem.getLibrary().addBook(dsBook);
onlineReaderSystem.getLibrary().addBook(algoBook);
User user1 = new User(1, " ", "Ram");
User user2 = new User(2, " ", "Gopal");
onlineReaderSystem.getUserManager().addUser(user1);
onlineReaderSystem.getUserManager().addUser(user2);
onlineReaderSystem.setActiveBook(algoBook);
onlineReaderSystem.setActiveUser(user1);
onlineReaderSystem.getDisplay().turnPageForward();
onlineReaderSystem.getDisplay().turnPageForward();
onlineReaderSystem.getDisplay().turnPageBackward();
}
}
// This code is contributed by 29AjayKumar GeeksforGeeks 系统设计课程
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