extends generic SwingWorker : SwingWorker « Swing « Java Tutorial

1. Java Tutorial
2. Swing
3. SwingWorker

/*
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 *
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 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
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 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.List;
import java.util.Random;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
import javax.swing.border.Border;

public class Flipper extends JFrame implements ActionListener {
  private final GridBagConstraints constraints;
  private final JTextField headsText, totalText, devText;
  private final Border border = BorderFactory.createLoweredBevelBorder();
  private final JButton startButton, stopButton;
  private FlipTask flipTask;

  private JTextField makeText() {
    JTextField t = new JTextField(20);
    t.setEditable(false);
    t.setHorizontalAlignment(JTextField.RIGHT);
    t.setBorder(border);
    getContentPane().add(t, constraints);
    return t;
  }

  private JButton makeButton(String caption) {
    JButton b = new JButton(caption);
    b.setActionCommand(caption);
    b.addActionListener(this);
    getContentPane().add(b, constraints);
    return b;
  }

  public Flipper() {
    super("Flipper");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Make text boxes
    getContentPane().setLayout(new GridBagLayout());
    constraints = new GridBagConstraints();
    constraints.insets = new Insets(3, 10, 3, 10);
    headsText = makeText();
    totalText = makeText();
    devText = makeText();

    // Make buttons
    startButton = makeButton("Start");
    stopButton = makeButton("Stop");
    stopButton.setEnabled(false);

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

  private static class FlipPair {
    private final long heads, total;

    FlipPair(long heads, long total) {
      this.heads = heads;
      this.total = total;
    }
  }

  private class FlipTask extends SwingWorker<Void, FlipPair> {
    @Override
    protected Void doInBackground() {
      long heads = 0;
      long total = 0;
      Random random = new Random();
      while (!isCancelled()) {
        total++;
        if (random.nextBoolean()) {
          heads++;
        }
        publish(new FlipPair(heads, total));
      }
      return null;
    }

    @Override
    protected void process(List<FlipPair> pairs) {
      FlipPair pair = pairs.get(pairs.size() - 1);
      headsText.setText(String.format("%d", pair.heads));
      totalText.setText(String.format("%d", pair.total));
      devText.setText(String.format("%.10g", ((double) pair.heads)
          / ((double) pair.total) - 0.5));
    }
  }

  public void actionPerformed(ActionEvent e) {
    if ("Start" == e.getActionCommand()) {
      startButton.setEnabled(false);
      stopButton.setEnabled(true);
      (flipTask = new FlipTask()).execute();
    } else if ("Stop" == e.getActionCommand()) {
      startButton.setEnabled(true);
      stopButton.setEnabled(false);
      flipTask.cancel(true);
      flipTask = null;
    }

  }

  public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
      public void run() {
        new Flipper();
      }
    });
  }
}