Java Swing How to - Use SwingWorker to handle lengthy task

Question

We would like to know how to use SwingWorker to handle lengthy task.
Answer

/*//from   w  w  w.java 2 s  .  co m
   This program is a part of the companion code for Core Java 8th ed.
   (http://horstmann.com/corejava)

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.List;

import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingWorker;

/**
 * This program demonstrates the use of a progress bar to monitor the progress
 * of a thread.
 * 
 * @version 1.04 2007-08-01
 * @author Cay Horstmann
 */
public class Main {
  public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
      public void run() {
        JFrame frame = new ProgressBarFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
      }
    });
  }
}

/**
 * A frame that contains a button to launch a simulated activity, a progress
 * bar, and a text area for the activity output.
 */
class ProgressBarFrame extends JFrame {
  public ProgressBarFrame() {
    setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

    // this text area holds the activity output
    textArea = new JTextArea();

    // set up panel with button and progress bar

    final int MAX = 1000;
    JPanel panel = new JPanel();
    startButton = new JButton("Start");
    progressBar = new JProgressBar(0, MAX);
    progressBar.setStringPainted(true);
    panel.add(startButton);
    panel.add(progressBar);

    checkBox = new JCheckBox("indeterminate");
    checkBox.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent event) {
        progressBar.setIndeterminate(checkBox.isSelected());
        progressBar.setStringPainted(!progressBar.isIndeterminate());
      }
    });
    panel.add(checkBox);
    add(new JScrollPane(textArea), BorderLayout.CENTER);
    add(panel, BorderLayout.SOUTH);

    // set up the button action

    startButton.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent event) {
        startButton.setEnabled(false);
        activity = new SimulatedActivity(MAX);
        activity.execute();
      }
    });
  }

  private JButton startButton;
  private JProgressBar progressBar;
  private JCheckBox checkBox;
  private JTextArea textArea;
  private SimulatedActivity activity;

  public static final int DEFAULT_WIDTH = 400;
  public static final int DEFAULT_HEIGHT = 200;

  class SimulatedActivity extends SwingWorker<Void, Integer> {
    /**
     * Constructs the simulated activity that increments a counter from 0 to a
     * given target.
     * 
     * @param t
     *          the target value of the counter.
     */
    public SimulatedActivity(int t) {
      current = 0;
      target = t;
    }

    protected Void doInBackground() throws Exception {
      try {
        while (current < target) {
          Thread.sleep(100);
          current++;
          publish(current);
        }
      } catch (InterruptedException e) {
      }
      return null;
    }

    protected void process(List<Integer> chunks) {
      for (Integer chunk : chunks) {
        textArea.append(chunk + "\n");
        progressBar.setValue(chunk);
      }
    }

    protected void done() {
      startButton.setEnabled(true);
    }

    private int current;
    private int target;
  }
}