Question

In order to decrease server overload while searching,I’m going to provide delay for keyboard input.

use case:
1. user types symbols
2. if delay between typing symbols < 1 second,that search is NOT performed immediately and waiting when delay after last typed symbol is > 1second
3. if delay between typing symbols > 1 second,that search performed immediately

Is there best practises in JSE or in mobile Java(Blackberry)?

Looks like I should use TimerTask and Timer APIs for such case.Is it?

Answer 1

According to Java concurrency bible ‘Java concurrency in practice‘

… Timer has some drawbacks, and ScheduledThreadPoolExecutor should be thought of as its replacement.

Thus, I would do something like this example:

public class DelayedSearch extends JFrame {
    public DelayedSearch() {
        final JPanel panel = new JPanel(new BorderLayout());
        final JTextField field = new JTextField(30);
        panel.add(field, BorderLayout.NORTH);
        final JLabel status = new JLabel(" ");
        panel.add(status, BorderLayout.SOUTH);
        this.add(panel);
        this.pack();
        final ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
        field.addKeyListener(new KeyAdapter() {
            private ScheduledFuture<?> scheduled;
            @Override
            public void keyTyped(KeyEvent e) {
                if (scheduled != null) scheduled.cancel(false);
                scheduled = executor.schedule(new Runnable() {
                    @Override
                    public void run() { // Perform search here. Just set status for demo.
                        status.setText("Search: " + field.getText());
                    }
                }, 1, TimeUnit.SECONDS);
            }
        });
    }
    public static void main(String[] args) {
        new DelayedSearch().setVisible(true);
    }
}

Note: I’m updating the status from a thread other than the EDT here which is illegal, but you get the idea.

EDIT: based upon great comments below (thanks!) Timer will work in this simple case, and it makes it easy to use a daemon thread (although it does have problems with tasks that throw exceptions, as described in the book). To do this replace above executor and listener as follows:

        ...
        final Timer timer = new Timer(true); // use daemon thread.
        field.addKeyListener(new KeyAdapter() {
            private TimerTask task;
            @Override
            public void keyTyped(KeyEvent e) {
                if(task != null)task.cancel();
                task = new TimerTask() {
                    @Override
                    public void run() {
                        status.setText("Search: " + field.getText());
                    }
                };
                timer.schedule(task, 1000);
            }
        });