JProgressBar from Oracle

I've downloaded a small Java project from oracle website to create a progress bar.

I understand it, but I need to apply it in a different way, the application is creating a thread in the background so the progress bar can be updated accordingly (doInBackground()).

My question is, how can I replace this kind of process in the background in this application by a method from my application (method is just doing a kind of batch processing on a database), can someone help please?

Here is code by Oracle:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.beans.*; 
import java.util.Random;


public class ProgressBarDemo2 extends JPanel
       implements ActionListener, PropertyChangeListener {

private JProgressBar progressBar;
private JButton startButton;
private JTextArea taskOutput;
private Task task;

class Task extends SwingWorker<Void, Void> {
    /*
     * Main task. Executed in background thread.
     */
    @Override
    public Void doInBackground() {
        Random random = new Random();
        int progress = 0;
        //Initialize progress property.
        setProgress(0);
        //Sleep for at least one second to simulate "startup".
        try {
            Thread.sleep(1000 + random.nextInt(2000));
        } catch (InterruptedException ignore) {}
        while (progress < 100) {
            //Sleep for up to one second.
            try {
                Thread.sleep(random.nextInt(1000));
            } catch (InterruptedException ignore) {}
            //Make random progress.
            progress += random.nextInt(10);
            setProgress(Math.min(progress, 100));
        }
        return null;
    }

    /*
     * Executed in event dispatch thread
     */
    public void done() {
        Toolkit.getDefaultToolkit().beep();
        startButton.setEnabled(true);
        taskOutput.append("Done!\n");
    }
}

public ProgressBarDemo2() {
    super(new BorderLayout());

    //Create the demo's UI.
    startButton = new JButton("Start");
    startButton.setActionCommand("start");
    startButton.addActionListener(this);

    progressBar = new JProgressBar(0, 100);
    progressBar.setValue(0);

    //Call setStringPainted now so that the progress bar height
    //stays the same whether or not the string is shown.
    progressBar.setStringPainted(true); 

    taskOutput = new JTextArea(5, 20);
    taskOutput.setMargin(new Insets(5,5,5,5));
    taskOutput.setEditable(false);

    JPanel panel = new JPanel();
    panel.add(startButton);
    panel.add(progressBar);

    add(panel, BorderLayout.PAGE_START);
    add(new JScrollPane(taskOutput), BorderLayout.CENTER);
    setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
}

/**
 * Invoked when the user presses the start button.
 */
public void actionPerformed(ActionEvent evt) {
    progressBar.setIndeterminate(true);
    startButton.setEnabled(false);
    //Instances of javax.swing.SwingWorker are not reusuable, so
    //we create new instances as needed.
    task = new Task();
    task.addPropertyChangeListener(this);
    task.execute();
}

/**
 * Invoked when task's progress property changes.
 */
public void propertyChange(PropertyChangeEvent evt) {
    if ("progress" == evt.getPropertyName()) {
        int progress = (Integer) evt.getNewValue();
        progressBar.setIndeterminate(false);
        progressBar.setValue(progress);
        taskOutput.append(String.format(
                    "Completed %d%% of task.\n", progress));
    }
}

/**
 * Create the GUI and show it. As with all GUI code, this must run
 * on the event-dispatching thread.
 */
private static void createAndShowGUI() {
    //Create and set up the window.
    JFrame frame = new JFrame("ProgressBarDemo2");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Create and set up the content pane.
    JComponent newContentPane = new ProgressBarDemo2();
    newContentPane.setOpaque(true); //content panes must be opaque
    frame.setContentPane(newContentPane);

    //Display the window.
    frame.pack();
    frame.setVisible(true);
}

public static void main(String[] args) {
    //Schedule a job for the event-dispatching thread:
    //creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGUI();
        }
    });
}
}