Question

i’m programming a blackjack (single thread) for a university project and the dealer is the computer (e.g. no player action)…

Does someone know how can I program in Java something like this:

while (dealerpoints < 17)
    open card and repaint frame
    wait 1 sec (to run again the condition test for while)

THe thing is, I don’t want all dealer cards painted at once…

Thanks in advance,
Gabriel Sotero

UPDATE: this is my code (that doesn’t work)

        while (Dealer.getInstance().dealerPoints < 17){

            Dealer.getInstance().openCard();
            try {
                Thread.sleep(100);
            }
            catch (InterruptedException e){ }
        }

openCard declaration:

    private void openCard(){

        Card temp;

        temp = Deck.getInstance().myPop();
        Dealer.getInstance().cards.add(temp);
        Dealer.getInstance().dealerPoints += temp.getValue(); 
        MainPanel.getInstance().updateDealerLabel(Dealer.getInstance().dealerPoints);
        MainPanel.getInstance().repaint();

    }

Answer 1

You can’t block the Event Dispatching Thread as it is responsible for (amongst other things) processing re-paint requests. So all the time you’re waiting, the UI is not begin updated. This includes using loops and Thread#sleep.

One solution is to use a SwingWorker, but, it’s unreliable in terms of when it will call an update back to the UI.

The other solution would be to use a javax.swing.Timer which will trigger a call back every n periods and is executed within the Event Dispatching Thread…

Something like…

Timer dealerTimer= new Timer(1000, new ActionListener() {
    public void actionListener(ActionEvent evt) {
        if (Dealer.getInstance().dealerPoints < 17) {
            Dealer.getInstance().openCard();
        } else {
            ((Timer)evt.getSource()).stop();
        }
    }
});
dealerTimer.setRepeats(true);
dealerTimer.start();

What I would do, is declare dealerTimer as a class field. When required, I would simply call dealerTimer.restart() to get the timer to restart. You might also want to check dealerTimer.isRunning() to make sure that the timer isn’t already running 😉

You might like to have a read through Concurrency in Swing for some more information