Design a Social Media Platform like Facebook
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Design a Social Media Platform like Facebook
Problem Statement
Design a social media platform where users can create accounts, make posts, follow other users, like and comment on posts, and view a personalized feed. The system should handle basic social interactions and generate a feed based on user connections.
Asked In Companies
Meta Google LinkedIn Twitter Amazon Microsoft Netflix Pinterest Salesforce Adobe Oracle Flipkart
Functional Requirements
- Users should be able to register and login
- Users should be able to create posts
- Users should be able to follow/unfollow other users
- Users should be able to like and comment on posts
- Users should be able to view a feed of posts from followed users
- Feed should show latest posts first
Objects Required
- User
- Post
- Comment
- SocialGraph (Follow system)
- FeedService
User Class
import java.util.*;
public class User {
private String userId;
private String name;
private Set<User> following = new HashSet<>();
private List<Post> posts = new ArrayList<>();
public User(String userId, String name) {
this.userId = userId;
this.name = name;
}
public void follow(User user) {
following.add(user);
}
public void unfollow(User user) {
following.remove(user);
}
public void createPost(Post post) {
posts.add(post);
}
public Set<User> getFollowing() {
return following;
}
public List<Post> getPosts() {
return posts;
}
public String getName() {
return name;
}
}The constructor initializes a user with a unique id and name.
The follow() method adds another user to the following list, enabling their posts to appear in the feed.
The unfollow() method removes a user from the following list, stopping their posts from appearing in the feed.
The createPost() method allows a user to publish a new post and store it in their personal post list.
Post Class
import java.time.LocalDateTime;
import java.util.*;
public class Post {
private String postId;
private User author;
private String content;
private LocalDateTime timestamp;
private Set<User> likes = new HashSet<>();
private List<Comment> comments = new ArrayList<>();
public Post(String postId, User author, String content) {
this.postId = postId;
this.author = author;
this.content = content;
this.timestamp = LocalDateTime.now();
}
public void like(User user) {
likes.add(user);
}
public void addComment(Comment comment) {
comments.add(comment);
}
public LocalDateTime getTimestamp() {
return timestamp;
}
public User getAuthor() {
return author;
}
public String getContent() {
return content;
}
}The constructor creates a post with author, content, and automatically assigns timestamp.
The like() method adds a user to the like set, ensuring a user can like a post only once.
The addComment() method attaches a comment to the post for discussion.
Comment Class
import java.time.LocalDateTime;
public class Comment {
private String commentId;
private User user;
private String message;
private LocalDateTime timestamp;
public Comment(String commentId, User user, String message) {
this.commentId = commentId;
this.user = user;
this.message = message;
this.timestamp = LocalDateTime.now();
}
}The constructor initializes a comment with user, message, and timestamp.
The class represents user-generated responses on posts.
FeedService Class
import java.util.*;
public class FeedService {
public List<Post> getFeed(User user) {
List<Post> feed = new ArrayList<>();
for (User u : user.getFollowing()) {
feed.addAll(u.getPosts());
}
feed.sort((a, b) ->
b.getTimestamp().compareTo(a.getTimestamp())
);
return feed;
}
}The getFeed() method builds a timeline for a user by collecting posts from all followed users.
It sorts posts in reverse chronological order so that the newest content appears first.
SocialMediaPlatform Class
import java.util.*;
public class SocialMediaPlatform {
private List<User> users = new ArrayList<>();
public User registerUser(String userId, String name) {
User user = new User(userId, name);
users.add(user);
return user;
}
public Post createPost(User user, String postId, String content) {
Post post = new Post(postId, user, content);
user.createPost(post);
return post;
}
}The platform class manages user registration and post creation.
The registerUser() method creates and stores a new user in the system.
The createPost() method allows a user to publish a post and links it to their account.
Main Class
public class Main {
public static void main(String[] args) {
SocialMediaPlatform platform = new SocialMediaPlatform();
User u1 = platform.registerUser("U1", "Alice");
User u2 = platform.registerUser("U2", "Bob");
u1.follow(u2);
platform.createPost(u2, "P1", "Hello from Bob!");
FeedService feedService = new FeedService();
System.out.println("Feed for Alice:");
for (Post post : feedService.getFeed(u1)) {
System.out.println(post.getContent());
}
}
}The main method demonstrates a simple flow where users register, follow each other, create posts, and generate a feed.