Multiple threads..?

[malcolm bailey]

Hello.
I would like to know if it's possible to have two (or more) independent threads in the same class working concurrently, and if so, how do I do it? In my application, I'm trying to have a thread continually sending messages, and another continually listening.
Thanks in advance, Malc

[Alex Zhang]

If U mean that class will have two instances of thread, surely U can.

[malcolm bailey]

..I'm not sure how to do it, though, as I'm fairly new to this..

[Peter den Haan]

Don't expect any of the following to work, I'm just making it up as I go... what you're looking for is the classic producer/consumer thing. A message box.

public class MessageBox {
   private Object _message;
   public synchronized void send(Object message)
   throws InterruptedException {
      while (_message != null) {
         wait();
      }
      _message = message;
      notifyAll();
   }
   public synchronized Object receive()
   throws InterruptedException {
      while (_message == null) {
         wait();
      }
      Object message = _message;
      _message = null;
      notifyAll();
      return message;
   }
}

The above class implements a threadsafe message box that will hold a single message. There may be multiple threads posting messages, and/or multiple threads receiving messages. If you want to get fancy you can decouple senders and receivers by adding a buffer list that will hold more than one message, etc.
A simple sender could look like

public class Sender extends Thread {
   private MessageBox _box;
   public Sender(MessageBox box) {
      _box = box;
   }
   public void run() {
      try {
         Random random = new Random();
         while (true) {
            Object message = this + System.currentTimeMillis();
            _box.send(message);
            Thread.sleep(500 + random.nextInt(1000));
         }
      } catch(InterruptedException e) {
         System.out.println(this + " interrupted");
      }
   }
}

This sender will send a message through the mailbox every 0.5-1.5 seconds. A receiver could look like

public class Sender extends Thread {
   private MessageBox _box;
   public Receiver(MessageBox box) {
      _box = box;
   }
   public void run() {
      try {
         Random random = new Random();
         while (true) {
            Object message = _box.receive();
            System.out.println(
               "received by " + this +
               " at " + System.currentTimeMillis() + 
               ": " + message);
            Thread.sleep(500 + random.nextInt(1000));
         }
      } catch(InterruptedException e) {
         System.out.println(this + " interrupted");
      }
   }
}

Write a main() that will create any number of senders and receivers, start() them, and off you go. After fixing the undoubted stupidities that crept in my code of course
- Peter

[malcolm bailey]

Thanks Peter, I'll see what I can do...

[Leela]

Originally posted by Alex Zhang:
If U mean that class will have two instances of thread, surely U can.

Hi,
I there are two/more instances of a thread &call the start method on all of them,how many run methods do we need and what will be the result.
Thanks