Updating Swing GUI with while loop and delay

Question

I have a while loop that is supposed to update the program data and the GUI, but the GUI part freezes until the while loop is done executing.

Here is my code:

while(game.getCompTotal() < 17) {
    try {
        Thread.sleep(2500);
    } catch (Exception ex){
        ex.printStackTrace();
    }
    game.compHit();           // Program data update

    updateCardPanels();       // GUI update -- Does not update until the while loop finishes.

    if(game.checkCompBust()){
        if(JOptionPane.showConfirmDialog(this, "Dealer Busted.  Play again?") == JOptionPane.YES_OPTION){
            init();           // Reset
        }   
    }
}

I have tried using SwingUtilities.invokeLater() and a Swing Timer but I do not really get how SwingUtilities.invokeLater() works or how to use a Swing Timer on the EDT. My question is how can I have the GUI update at the same time as the program data in the while loop?

Here is my attempted invokeLater() code:

SwingUtilities.invokeLater(new Runnable() {
    public void run() {
        Timer t = new Timer(100, new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e) {
                updateCardPanels();
            }
        });
        t.setInitialDelay(0);
        t.start();
    }
});

Answer 1

1. Looks like your while loop is on EDT and thats why it freezes GUI while it is executing. Never call Thread.sleep on EDT.

2. All SwingUtilities.invokeLater does is puts the Runnable on a queue so that EDT would run it at some point in time. The SwingUtilities.invokeLater should be run from a non EDT thread. Starting Swing Timer with SwingUtilities.invokeLater is not required. You can start it directly from EDT.

3. Swing timer uses a separate thread that runs and periodically calls specified ActionListener on EDT thread.

You can replace the while loop with swing timer (lets say with 1sec interval) and check game.getCompTotal() < 17 condition inside its actionPerformed call.