Observer in Chat Application
This program integrates Observer pattern in chat app.
Problem Statement
Write a Java program where ChatRoom notifies users of new messages.
Source Code
| 1 | import java.util.*; |
| 2 | interface User { void update(String msg); } |
| 3 | class ChatRoom { |
| 4 | List<User> users=new ArrayList<>(); |
| 5 | void addUser(User u){ users.add(u); } |
| 6 | void sendMessage(String msg){ for(User u:users) u.update(msg); } |
| 7 | } |
| 8 | class ConcreteUser implements User { |
| 9 | String name; |
| 10 | ConcreteUser(String n){ name=n; } |
| 11 | public void update(String msg){ System.out.println(name+" received: "+msg); } |
| 12 | } |
| 13 | public class ChatApp { |
| 14 | public static void main(String[] args) { |
| 15 | System.out.println("Eduinq Chat App"); |
| 16 | ChatRoom cr=new ChatRoom(); |
| 17 | cr.addUser(new ConcreteUser("User1")); |
| 18 | cr.addUser(new ConcreteUser("User2")); |
| 19 | cr.sendMessage("Hello Everyone"); |
| 20 | } |
| 21 | } |
Program Output
Eduinq Chat App User1 received: Hello Everyone User2 received: Hello Everyone
Explanation
ChatRoom acts as Subject. - Users act as Observers. - Message broadcast demonstrates Observer in enterprise apps. Conclusion: Shows Observer integration in chat application.