Question

I’m writing my first non-trivial Java app that uses:

• networking
• a GUI
• threads

It’s a IM program. When I send a message, the server doesn’t output what it should. I’m sorry this description is so bad, but I don’t know how to narrow the problem down further.

public class MachatServer {
     //snip
     public static void sendMessage(int targetId, int fromId, String message) {
         ConnectedClient targetClient = getClient(targetId);
         // Also runs
         System.out.println("Sending message: " + message + "\n\nfrom " + fromId +  " to " + targetId);
         targetClient.addOutCommand("/message:" + fromId + ":" + message + "\n");
     }
}
class ConnectedClient implements Runnable {
public void run() {
    String contact;
    contact = s.getInetAddress().toString();
    System.out.println("Connected to " + contact);
    try {
        out.write("/connected" + "\n");
        out.flush();
        String command;
        while(true) {
            if(shouldExit) {
                s.close();
                break;
            }
            if(in.hasNextLine()) {
                command = in.nextLine();
                commandProcessor.addInCommand(command);
            }
            Thread.sleep(100);
         }
    } catch(Exception e) {
        e.printStackTrace();
    }
}
// snip
public void addOutCommand(String command) {
    commandProcessor.addOutCommand(command);
    //
    // My guess is that the problem is with this method as the next line
    // Does not print out.
    //
    //
    System.out.println("" + thisId + " recieved to send: " + command);
}
}
class CommandProcessor implements Runnable {  
// snip  
public void run() {
    String currentCommandIn;
    String currentCommandOut;
    while(true) {
        try {
            currentCommandIn = inQueue.poll();
            if(currentCommandIn != null) {
                System.out.println("Processing: " + currentCommandIn);
                String[] commandArr = CommandParser.parseRecievedCommand(currentCommandIn);
                if(commandArr[0].equalsIgnoreCase("message")) {
                    int target = Integer.parseInt(commandArr[1]);
                    String message = commandArr[2];
                    // This definetly runs
                    System.out.println("Message sending to: " + target);
                    MachatServer.sendMessage(target, this.conId, message);
                } else if(commandArr[0].equalsIgnoreCase("quit")) {
                    // Tell the server to disconnect us.
                    MachatServer.disconnect(conId);
                    break;
                }
            currentCommandOut = outQueue.poll();
            if(currentCommandOut != null) {
                try {
                    out.write(currentCommandOut + "\n");
                    System.out.println(currentCommandOut + "sent");
                    out.flush();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
      } catch(Exception e) {
            e.printStackTrace();
      }    
    public synchronized void addOutCommand(String command) {
    if(command != null) {
        try {
            outQueue.push(command);
        } catch(Exception e) {
            System.out.println(command);
            e.printStackTrace();
        }
        // Does not print
        System.out.println("Ready to send: " + command);
    } else {
        System.out.println("Null command recieved");
    }
    //snip
}

The full source code is at my github, in case I have narrowed the problem down incorrectly.

The expected output should be when I telnet in and send “/message:0:test”, it should send “/message:myid:test” to the client with ID 0. The actual output is nothing.

Answer 1

The field outQueue is uninitialized in CommandProcessor, and you commented out the printStackTrace() that would have helped you figure it out.