final fix

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+    "java.compile.nullAnalysis.mode": "automatic"
+}

README.md

@@ -0,0 +1,11 @@
+## Task 2
+program starts, asks user id, and corespondent id. 
+
+#### commands
+- `exit` program exits
+
+## Task 3
+Task 3 follows the same proccess as Task 2. but implements additional commands to block and unblock correspondents
+- `exit` program exits
+- `-b <user>` block a user
+- `-u <user>` unblocks user

week2_TinsaeGhilay/Task2/src/main/java/org/distributed/ChatHandler.java

@@ -1,52 +1,44 @@
 package org.distributed;
-/**
- * ChatHandler.java
- * by Tinsae Ghilay
- * Handles chat session, message sending and receiving using JMS queues.
- * Uses ActiveMQ as the message broker.
- * done for Distributed Systems Course - Week 2 Task 2
- * Date: June 2024
- */
-
 import java.util.Scanner;
 import javax.jms.*;
 import org.apache.activemq.ActiveMQConnectionFactory;
 
-// ChatHandler class to manage chat sessions
 public class ChatHandler {
 
-    // chatting ids
     private String userId, corespondent;
     private Connection connection;
-    private Session session;
+    private Session senderSession, receiverSession;
     private final String TAG = "Task2_queue_";
     private final String BROKER_URL = "tcp://localhost:61616";
-
+    /**
-    // Initialize connection and session
+     * Initialize JMS session
+     * @throws JMSException
+     */
     public void initializeSession() throws JMSException {
         ConnectionFactory factory = new ActiveMQConnectionFactory(BROKER_URL);
         this.connection = factory.createConnection();
         this.connection.start();
-        this.session = this.connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
+        this.senderSession = this.connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
+        this.receiverSession = this.connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
     }
 
-    // Start continuous conversation with multiple receivers
+    /**
+     * Start conversation loop
+     * @param sc
+     * @throws JMSException
+     */
     public void startConversation(Scanner sc) throws JMSException {
 
-        // Initialize all producers and consumers
+        // init receiving thread
-        Thread t = setupReceiver();
+        Thread t = setupReceiver(userId);
 
         // Continuous input loop
         try {
-            while (sc.hasNextLine()) {
+            while (sc.hasNextLine()){
-                String line = sc.nextLine();
 
-                // Send message to receiver
+                // handle user input and send messages
-                sendMessage(createProducer(), line);
+                // or if exit command, break loop
-
+                if(!respond(sc)){ 
-                // Exit condition
-                if (line.equalsIgnoreCase("exit")) {
-                    System.out.println("Exiting conversation...");
                     break;
                 }
             }
@@ -57,71 +49,115 @@ public class ChatHandler {
         }
     }
 
+    /**
+     * Handle user input and send messages
+     * @param sc
+     * @throws JMSException
+     */
+    private boolean respond(Scanner sc) throws JMSException {
+        String line = sc.nextLine();
+
+        // exit condition
+        if (line.equalsIgnoreCase("exit")) {
+            System.out.println("Exiting conversation...");
+            return false;
+        }
+
+        // Send message to receiver
+        sendMessage(createProducer(corespondent), line);
+        return true;
+    }
+
+
     // Setup producer and consumer for a receiver
-    private Thread setupReceiver() throws JMSException {
+    private Thread setupReceiver(String receiver) throws JMSException {
+        MessageConsumer contact = createConsumer();
 
-        MessageConsumer consumer = createConsumer();
+        // add consumer to contacts map
-
+        return getThread(contact);
-        return getThread(consumer);
     }
 
-    // Create producer queue for sending messages
+    /**
-    private MessageProducer createProducer() throws JMSException {
+     * Create a producer for a given contact ID so we can send messages
-        String from = TAG + userId;
+     * @param id
-        Queue prod = session.createQueue(from);
+     * @return MessageProducer
-        return session.createProducer(prod);
+     * @throws JMSException
+     */
+    private MessageProducer createProducer(String id) throws JMSException {
+        String from = TAG + id;
+        Queue prod = senderSession.createQueue(from);
+        return senderSession.createProducer(prod);
     }
 
-    // Create consumer queue for receiving messages
+
+    /**
+     * Subscribe to topics meant for this user
+     * @return MessageConsumer
+     * @throws JMSException
+     */
     private MessageConsumer createConsumer() throws JMSException {
-        String to = TAG+ getCorespondent();
+        String to = TAG + userId;
-        Queue cons = session.createQueue(to);
+        Queue cons = receiverSession.createQueue(to);
-        return session.createConsumer(cons);
+        return receiverSession.createConsumer(cons);
     }
 
-    // Send a message to the producer
+    /**
+     * Send a messag
+     * @param producer
+     * @param line
+     * @throws JMSException
+     */
     private void sendMessage(MessageProducer producer, String line) throws JMSException {
-        TextMessage m = session.createTextMessage(line);
+
+        TextMessage m = senderSession.createTextMessage(line);
+        // add sender identity to message
         m.setStringProperty("sender", userId);
         producer.send(m);
     }
 
-    // Close connection and session
+    /**
+     * Close session and connection
+     * @throws JMSException
+     */
     public void closeSession() throws JMSException {
-        if (session != null) {
+        if (senderSession != null) {
-            session.close();
+            senderSession.close();
+        }
+        if( receiverSession != null) {
+            receiverSession.close();
         }
         if (connection != null) {
             connection.close();
         }
     }
 
-    // Returns a thread object to handle receiving messages
+    /**
+     * Returns a thread object to handle receiving messages
+     * @param consumer
+     * @return Thread
+     */
     private Thread getThread(MessageConsumer consumer) {
+
         Thread receivingThread = new Thread(() -> {
             try {
-                // continously listen for messages
+
                 while (!Thread.currentThread().isInterrupted()) {
-                    Message msg = consumer.receive(300);
+
+                    // receive message with timeout
+                    Message msg = consumer.receive(100); // 100ms timeout
                     if (msg instanceof TextMessage tm) {
 
+                        // message contents
                         String sender = tm.getStringProperty("sender");
-                        // Status handling for online/offline
-                        if(tm.getText().isBlank() || tm.getText().isEmpty()) {
-                            System.out.println("> " + sender + " is online.");
-                            continue;
-                        }
-                      
-                        // Exit condition because correspondent went offline
-                        if(tm.getText().equalsIgnoreCase("exit")) { 
-                            System.out.println("> " + sender + " is offline.");
-                            continue;
-                        }
-
-                        // Display received message can be from anyone
-                        //String sender = tm.getStringProperty("sender");
                         String body = tm.getText();
-                        System.out.println("[" + sender + "]: " + body);
+
+                        boolean isEmptyMessage = body.isBlank() || body.isEmpty();
+
+                        // display only if not blocked and not empty
+                        if (!isEmptyMessage) {
+                            System.out.println("[" + sender + "]: " + body);
+                        }
+                        
                     }
                 }
             } catch (javax.jms.JMSException e) {
@@ -131,30 +167,48 @@ public class ChatHandler {
                 }
             }
         });
+
+        
         receivingThread.start();
         // we are returning this so we can interrupt it later
         return receivingThread;
     }
 
-    // Prompt for user ID
+
+    /**
+     * Prompt for user ID
+     * @param sc
+     */
     public void promptForUser(Scanner sc){
 
         System.out.print("Enter your user ID: ");
         setUserId(prompt(sc));
         // Instructions
-        System.out.print("Welcome "+getUserId());
+        System.out.println("Welcome "+getUserId());
-        System.out.println(" -> Type 'exit' to quit.");
+        printCommands();
     }
 
-    // Prompt for correspondent ID
+    private void printCommands() {
+        System.out.println("- To exit the chat: exit");
+    }
+
+    /**
+     * Prompt for correspondent ID
+     * @param sc
+     */
     public void promptForCorespondent(Scanner sc){
 
         System.out.print("Who do you want to chat with? ");
-        setCorespondent(prompt(sc));
+        String contact = prompt(sc);
-        System.out.println("You can chat with: " + getCorespondent());
+        setCorespondent(contact);
+        System.out.println("You can start with: " + getCorespondent());
     }
 
-    // Generic prompt method prompts for whatever we need
+    /**
+     * Generic prompt method prompts for whatever we need
+     * @param sc Scanner object
+     * @return String
+     */
     private String prompt(Scanner sc) {
 
         String user = "";
@@ -189,5 +243,4 @@ public class ChatHandler {
     public void setCorespondent(String corespondent) {
         this.corespondent = corespondent;
     }
-
 }

week2_TinsaeGhilay/Task2/src/main/java/org/distributed/ChatHandler2.java

@@ -1,242 +0,0 @@
-package org.distributed;
-import java.util.Scanner;
-import javax.jms.*;
-import org.apache.activemq.ActiveMQConnectionFactory;
-
-public class ChatHandler2 {
-
-    private String userId, corespondent;
-    private Connection connection;
-    private Session senderSession, receiverSession;
-    private final String TAG = "Task2_queue_";
-    private final String BROKER_URL = "tcp://localhost:61616";
-    /**
-     * Initialize JMS session
-     * @throws JMSException
-     */
-    public void initializeSession() throws JMSException {
-        ConnectionFactory factory = new ActiveMQConnectionFactory(BROKER_URL);
-        this.connection = factory.createConnection();
-        this.connection.start();
-        this.senderSession = this.connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
-        this.receiverSession = this.connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
-    }
-
-    /**
-     * Start conversation loop
-     * @param sc
-     * @throws JMSException
-     */
-    public void startConversation(Scanner sc) throws JMSException {
-
-        // init receiving thread
-        Thread t = setupReceiver(userId);
-
-        // Continuous input loop
-        try {
-            while (sc.hasNextLine()){
-
-                // handle user input and send messages
-                // or if exit command, break loop
-                if(!respond(sc)){ 
-                    break;
-                }
-            }
-        } catch (Exception e) {
-            System.err.println("Error in continuous conversation: " + e.getMessage());
-        } finally {
-            t.interrupt();
-        }
-    }
-
-    /**
-     * Handle user input and send messages
-     * @param sc
-     * @throws JMSException
-     */
-    private boolean respond(Scanner sc) throws JMSException {
-        String line = sc.nextLine();
-
-        // exit condition
-        if (line.equalsIgnoreCase("exit")) {
-            System.out.println("Exiting conversation...");
-            return false;
-        }
-
-        // Send message to receiver
-        sendMessage(createProducer(corespondent), line);
-        return true;
-    }
-
-
-    // Setup producer and consumer for a receiver
-    private Thread setupReceiver(String receiver) throws JMSException {
-        MessageConsumer contact = createConsumer();
-
-        // add consumer to contacts map
-        return getThread(contact);
-    }
-
-    /**
-     * Create a producer for a given contact ID so we can send messages
-     * @param id
-     * @return MessageProducer
-     * @throws JMSException
-     */
-    private MessageProducer createProducer(String id) throws JMSException {
-        String from = TAG + id;
-        Queue prod = senderSession.createQueue(from);
-        return senderSession.createProducer(prod);
-    }
-
-
-    /**
-     * Subscribe to topics meant for this user
-     * @return MessageConsumer
-     * @throws JMSException
-     */
-    private MessageConsumer createConsumer() throws JMSException {
-        String to = TAG + userId;
-        Queue cons = receiverSession.createQueue(to);
-        return receiverSession.createConsumer(cons);
-    }
-
-    /**
-     * Send a messag
-     * @param producer
-     * @param line
-     * @throws JMSException
-     */
-    private void sendMessage(MessageProducer producer, String line) throws JMSException {
-
-        TextMessage m = senderSession.createTextMessage(line);
-        // add sender identity to message
-        m.setStringProperty("sender", userId);
-        producer.send(m);
-    }
-
-    /**
-     * Close session and connection
-     * @throws JMSException
-     */
-    public void closeSession() throws JMSException {
-        if (senderSession != null) {
-            senderSession.close();
-        }
-        if( receiverSession != null) {
-            receiverSession.close();
-        }
-        if (connection != null) {
-            connection.close();
-        }
-    }
-
-    /**
-     * Returns a thread object to handle receiving messages
-     * @param consumer
-     * @return Thread
-     */
-    private Thread getThread(MessageConsumer consumer) {
-
-        Thread receivingThread = new Thread(() -> {
-            try {
-
-                while (!Thread.currentThread().isInterrupted()) {
-
-                    // receive message with timeout
-                    Message msg = consumer.receive(100); // 100ms timeout
-                    if (msg instanceof TextMessage tm) {
-
-                        // message contents
-                        String sender = tm.getStringProperty("sender");
-                        String body = tm.getText();
-
-                        boolean isEmptyMessage = body.isBlank() || body.isEmpty();
-
-                        // display only if not blocked and not empty
-                        if (!isEmptyMessage) {
-                            System.out.println("[" + sender + "]: " + body);
-                        }
-                        
-                    }
-                }
-            } catch (javax.jms.JMSException e) {
-                // Silently handle interruption - normal shutdown behavior
-                if (!Thread.currentThread().isInterrupted()) {
-                    System.err.println("Error receiving message: " + e.getMessage());
-                }
-            }
-        });
-
-        
-        receivingThread.start();
-        // we are returning this so we can interrupt it later
-        return receivingThread;
-    }
-
-
-    /**
-     * Prompt for user ID
-     * @param sc
-     */
-    public void promptForUser(Scanner sc){
-
-        System.out.print("Enter your user ID: ");
-        setUserId(prompt(sc));
-        // Instructions
-        System.out.print("Welcome "+getUserId());
-        System.out.println(" -> Type 'exit' to quit.");
-    }
-
-    /**
-     * Prompt for correspondent ID
-     * @param sc
-     */
-    public void promptForCorespondent(Scanner sc){
-
-        System.out.print("Who do you want to chat with? ");
-        String contact = prompt(sc);
-        setCorespondent(contact);
-        System.out.println("You can start with: " + getCorespondent());
-    }
-
-    /**
-     * Generic prompt method prompts for whatever we need
-     * @param sc Scanner object
-     * @return String
-     */
-    private String prompt(Scanner sc) {
-
-        String user = "";
-
-        while (user.isEmpty()) {
-            try {
-                user = sc.next();
-
-            } catch (Exception e) {
-                System.err.println("Error reading correspondent ID: " + e.getMessage());
-                return null;
-            }
-        }
-        return user;
-    }
-
-    // Setters and getters
-    // user
-    public void setUserId(String userId) {
-        this.userId = userId;
-    }
-
-    public String getUserId() {
-        return userId;
-    }
-
-    // correspondent
-    public String getCorespondent() {
-        return corespondent;
-    }
-
-    public void setCorespondent(String corespondent) {
-        this.corespondent = corespondent;
-    }
-}

week2_TinsaeGhilay/Task3/src/main/java/org/distributed/ChatHandler.java

@@ -292,9 +292,19 @@ public class ChatHandler {
         setUserId(prompt(sc));
         // Instructions
         System.out.print("Welcome "+getUserId());
-        System.out.println(" -> Type 'exit' to quit.");
+        printCommands();
     }
 
+    /**
+     * Print available commands
+     */
+    private void printCommands() {
+        System.out.println("\nYou can use the following commands during the chat:");
+        System.out.println("- To block a contact: -b <contact_id>");
+        System.out.println("- To unblock a contact: -u <contact_id>");
+        System.out.println("- To exit the chat: exit");
+    }   
+
     /**
      * Prompt for correspondent ID
      * @param sc
@@ -309,7 +319,7 @@ public class ChatHandler {
             System.out.println(contact + " is currently blocked. Unblock to chat.");
             return;
         }
-        System.out.println("You can start with: " + getCorespondent());
+        System.out.println("You can start chatting with: " + getCorespondent());
     }
 
     /**