The part of my code that deals with threading. The sendMessage() method can be called from any thread and at any time. It posts a new message to send to the message queue and starts the sender thread if it isn't running. The sender thread polls the queue with a timeout, and processes the messages. If there are no more messages in the queue, the …

SMS Sender thread

private final LinkedBlockingQueue<Message> messageQueue = new LinkedBlockingQueue<Message>();

// The sender argument is an enum describing who sent the message: the user, the app, or the person on the other end.
public void sendMessage(String address, String message, Sender sender) {
    messageQueue.offer(Message.create(address, message, sender));
    startSenderThread();
}

private Thread senderThread;

private void startSenderThread(){

    if(senderThread == null || !senderThread.isAlive()){
        senderThread = new Thread(){
            @Override
            public void run() {
                loopSendMessage();
            }
        };

        senderThread.start();
    }
}

private void loopSendMessage(){
        Message queuedMessage;

        while(!Thread.interrupted()){
            try {
                queuedMessage = messageQueue.poll(10, TimeUnit.SECONDS);
            } catch (InterruptedException e) {
                EasyLog.e(SMSSenderDaemon.this, "SenderThread interrupted while polling.", e);
                continue;
            }
            if(queuedMessage != null)
                sendOrQueueMessage(queuedMessage);
            else
                break;
        }
}

// Queue in this context means storing the message in the database
// so it can be sent later.
private void sendOrQueueMessage(Message message){
//Irrelevant code omitted.
}