How to Use SwingWorker and Timer to Update JLabel with Results of Long Running Tasks in Java?

Use SwingWorker to Update JLabel Repeatedly with Results of Long Running Task

This question addresses the need to periodically update a JLabel with results from a long-running task. To achieve this using Java, one should employ a combination of Swing Timer and SwingWorker.

Swing Timer for Repeated Tasks

A Swing Timer provides a convenient way to schedule recurring tasks in a GUI. In this case, we will use the Timer to execute the long-running task at regular intervals.

SwingWorker for Long Running Tasks

SwingWorker is a subclass of SwingUtilities that enables performing tasks in a separate thread, keeping the GUI responsive. Here, SwingWorker will execute the long-running task of pinging a server and updating the JLabel with the result.

Example Implementation

The following code demonstrates how to implement this approach:

<code class="java">import java.awt.event.*;
import javax.swing.*;

public class PingLabelUpdater {

    public static void main(String[] args) {
        final JLabel label = new JLabel("0000");
        ActionListener timerListener = new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                new PingWorker().execute();
            }
        };
        Timer timer = new Timer(1000, timerListener);

        label.setFont(label.getFont().deriveFont(120f));
        JOptionPane.showMessageDialog(null, label, "stackoverflow.com", JOptionPane.INFORMATION_MESSAGE);
        timer.stop();
    }

    static class PingWorker extends SwingWorker {
        int time;
        @Override
        protected Object doInBackground() throws Exception {
            time = pingTime("stackoverflow.com");
            return new Integer(time);
        }
        @Override
        protected void done() {
            label.setText("" + time);
        }
    }

    public static int pingTime(String hostnameOrIP) {
        Socket socket = null;
        long start = System.currentTimeMillis();
        try {
            socket = new Socket(hostnameOrIP, 80);
        } catch (Exception e) {
        } finally {
            if (socket != null) {
                try {
                    socket.close();
                } catch (Exception e) {}
            }
        }
        long end = System.currentTimeMillis();
        return (int) (end - start);
    }
}</code>

In this example, the pingTime method establishes a connection to the specified server (stackoverflow.com) and measures the time it takes. The SwingWorker's doInBackground method performs the ping, and its done method updates the label with the ping time. The Timer is configured to execute the SwingWorker at an interval of 1000 milliseconds (1 second).

By combining Swing Timer and SwingWorker, we effectively update the JLabel with ping times without blocking the GUI thread, ensuring a responsive user interface while the task runs in the background.

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