Question

I am trying to write a java code that will give an alert at a specific time of day but I don’t know why I am failing(Please be gentle to my questions as I am totally new to programming). I have this code

    new ScheduledThreadPoolExecutor(1).schedule(new Runnable() {
    public void run() {
        if(Calendar.SECOND==30)
        {
            JOptionPane.showMessageDialog(null, "Hola Amigo");
        }
    }
}, 1, TimeUnit.SECONDS);

Should I try to refresh the page? Please help…

Answer 1

You are checking that a fixed constant value Calendar.SECOND (13) equals 30. Obviously, this will never be true so the dialog will never appear. You need to check this field in a Calendar instance.

Also using schedule means that the executor thread is only run once. Use scheduleAtFixedRate.

Also you would need to call showMessageDialog in the EDT to ensure that the call does not block the Executor Thread.

ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
scheduler.scheduleAtFixedRate(new Runnable() {
    public void run() {
        Calendar calendar = Calendar.getInstance();
        int second = calendar.get(Calendar.SECOND);
        if (second == 30) {
            SwingUtilities.invokeLater(new Runnable() {
                @Override
                public void run() {
                    JOptionPane.showMessageDialog(null, "Hola Amigo");
                }
            });
        }
    }
}, 1, 1, TimeUnit.SECONDS);

If you want to call the ExecutorService every 30 seconds rather than repeatly checking the current second, you could call

scheduler.scheduleAtFixedRate(myRunnable, 1, 30, TimeUnit.SECONDS);