java/6 : javax/swing/SwingWorker.java

SwingWorker
https://openjdk.java.net/
GPLv2 + Classpath Exception
/*
 * Copyright (c) 2005, 2009, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package javax.swing;

import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.beans.PropertyChangeEvent;

import java.lang.ref.WeakReference;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.List;

import java.util.concurrent.*;
import java.util.concurrent.locks.*;

import java.awt.event.*;

import sun.awt.AppContext;
import sun.swing.AccumulativeRunnable;

An abstract class to perform lengthy GUI-interacting tasks in a
dedicated thread.

When writing a multi-threaded application using Swing, there are
two constraints to keep in mind:
(refer to

  How to Use Threads
 for more details):

   Time-consuming tasks should not be run on the Event
       Dispatch Thread. Otherwise the application becomes unresponsive.
  
   Swing components should be accessed  on the Event
       Dispatch Thread only.
  



These constraints mean that a GUI application with time intensive
computing needs at least two threads:  1) a thread to perform the lengthy
task and 2) the Event Dispatch Thread (EDT) for all GUI-related
activities.  This involves inter-thread communication which can be
tricky to implement.
 SwingWorker is designed for situations where you need to have a long running task run in a background thread and provide updates to the UI either when done, or while processing. Subclasses of SwingWorker must implement the doInBackground method to perform the background computation. 

Workflow
 There are three threads involved in the life cycle of a SwingWorker : 



Current thread: The execute method is called on this thread. It schedules SwingWorker for the execution on a worker thread and returns immediately. One can wait for the SwingWorker to complete using the get methods. 


Worker thread: The doInBackground method is called on this thread. This is where all background activities should happen. To notify PropertyChangeListeners about bound properties changes use the firePropertyChange and getPropertyChangeSupport methods. By default there are two bound properties available: state and progress. 


Event Dispatch Thread: All Swing related activities occur on this thread. SwingWorker invokes the process and done methods and notifies any PropertyChangeListeners on this thread. 

Often, the Current thread is the Event Dispatch
Thread.
 Before the doInBackground method is invoked on a worker thread, SwingWorker notifies any PropertyChangeListeners about the state property change to StateValue.STARTED. After the doInBackground method is finished the done method is executed. Then SwingWorker notifies any PropertyChangeListeners about the state property change to StateValue.DONE. 
 SwingWorker is only designed to be executed once. Executing a SwingWorker more than once will not result in invoking the doInBackground method twice. 

Sample Usage

The following example illustrates the simplest use case.  Some
processing is done in the background and when done you update a Swing
component.
 Say we want to find the "Meaning of Life" and display the result in a JLabel. 
 final JLabel label; class MeaningOfLifeFinder extends SwingWorker<String, Object> { @Override public String doInBackground() { return findTheMeaningOfLife(); } @Override protected void done() { try { label.setText(get()); } catch (Exception ignore) { } } } (new MeaningOfLifeFinder()).execute(); 

The next example is useful in situations where you wish to process data
as it is ready on the Event Dispatch Thread.
 Now we want to find the first N prime numbers and display the results in a JTextArea. While this is computing, we want to update our progress in a JProgressBar. Finally, we also want to print the prime numbers to System.out. 
class PrimeNumbersTask extends SwingWorker<List<Integer>, Integer> { PrimeNumbersTask(JTextArea textArea, int numbersToFind) { //initialize } @Override public List<Integer> doInBackground() { while (! enough && ! isCancelled()) { number = nextPrimeNumber(); publish(number); setProgress(100 * numbers.size() / numbersToFind); } } return numbers; } @Override protected void process(List<Integer> chunks) { for (int number : chunks) { textArea.append(number + "\n"); } } } JTextArea textArea = new JTextArea(); final JProgressBar progressBar = new JProgressBar(0, 100); PrimeNumbersTask task = new PrimeNumbersTask(textArea, N); task.addPropertyChangeListener( new PropertyChangeListener() { public void propertyChange(PropertyChangeEvent evt) { if ("progress".equals(evt.getPropertyName())) { progressBar.setValue((Integer)evt.getNewValue()); } } }); task.execute(); System.out.println(task.get()); //prints all prime numbers we have got 
 Because SwingWorker implements Runnable, a SwingWorker can be submitted to an Executor for execution. 
Author: Igor Kushnirskiy
Type parameters: <T> – the result type returned by this SwingWorker's doInBackground and get methods
<V> – the type used for carrying out intermediate results by this SwingWorker's publish and process methods
Since: 1.6/**
 * An abstract class to perform lengthy GUI-interacting tasks in a
 * dedicated thread.
 *
 * <p>
 * When writing a multi-threaded application using Swing, there are
 * two constraints to keep in mind:
 * (refer to
 * <a href="http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html">
 *   How to Use Threads
 * </a> for more details):
 * <ul>
 *   <li> Time-consuming tasks should not be run on the <i>Event
 *        Dispatch Thread</i>. Otherwise the application becomes unresponsive.
 *   </li>
 *   <li> Swing components should be accessed  on the <i>Event
 *        Dispatch Thread</i> only.
 *   </li>
 * </ul>
 *
 * <p>
 *
 * <p>
 * These constraints mean that a GUI application with time intensive
 * computing needs at least two threads:  1) a thread to perform the lengthy
 * task and 2) the <i>Event Dispatch Thread</i> (EDT) for all GUI-related
 * activities.  This involves inter-thread communication which can be
 * tricky to implement.
 *
 * <p>
 * {@code SwingWorker} is designed for situations where you need to have a long
 * running task run in a background thread and provide updates to the UI
 * either when done, or while processing.
 * Subclasses of {@code SwingWorker} must implement
 * the {@link #doInBackground} method to perform the background computation.
 *
 *
 * <p>
 * <b>Workflow</b>
 * <p>
 * There are three threads involved in the life cycle of a
 * {@code SwingWorker} :
 * <ul>
 * <li>
 * <p>
 * <i>Current</i> thread: The {@link #execute} method is
 * called on this thread. It schedules {@code SwingWorker} for the execution on a
 * <i>worker</i>
 * thread and returns immediately. One can wait for the {@code SwingWorker} to
 * complete using the {@link #get get} methods.
 * <li>
 * <p>
 * <i>Worker</i> thread: The {@link #doInBackground}
 * method is called on this thread.
 * This is where all background activities should happen. To notify
 * {@code PropertyChangeListeners} about bound properties changes use the
 * {@link #firePropertyChange firePropertyChange} and
 * {@link #getPropertyChangeSupport} methods. By default there are two bound
 * properties available: {@code state} and {@code progress}.
 * <li>
 * <p>
 * <i>Event Dispatch Thread</i>:  All Swing related activities occur
 * on this thread. {@code SwingWorker} invokes the
 * {@link #process process} and {@link #done} methods and notifies
 * any {@code PropertyChangeListeners} on this thread.
 * </ul>
 *
 * <p>
 * Often, the <i>Current</i> thread is the <i>Event Dispatch
 * Thread</i>.
 *
 *
 * <p>
 * Before the {@code doInBackground} method is invoked on a <i>worker</i> thread,
 * {@code SwingWorker} notifies any {@code PropertyChangeListeners} about the
 * {@code state} property change to {@code StateValue.STARTED}.  After the
 * {@code doInBackground} method is finished the {@code done} method is
 * executed.  Then {@code SwingWorker} notifies any {@code PropertyChangeListeners}
 * about the {@code state} property change to {@code StateValue.DONE}.
 *
 * <p>
 * {@code SwingWorker} is only designed to be executed once.  Executing a
 * {@code SwingWorker} more than once will not result in invoking the
 * {@code doInBackground} method twice.
 *
 * <p>
 * <b>Sample Usage</b>
 * <p>
 * The following example illustrates the simplest use case.  Some
 * processing is done in the background and when done you update a Swing
 * component.
 *
 * <p>
 * Say we want to find the "Meaning of Life" and display the result in
 * a {@code JLabel}.
 *
 * <pre>
 *   final JLabel label;
 *   class MeaningOfLifeFinder extends SwingWorker&lt;String, Object&gt; {
 *       {@code @Override}
 *       public String doInBackground() {
 *           return findTheMeaningOfLife();
 *       }
 *
 *       {@code @Override}
 *       protected void done() {
 *           try {
 *               label.setText(get());
 *           } catch (Exception ignore) {
 *           }
 *       }
 *   }
 *
 *   (new MeaningOfLifeFinder()).execute();
 * </pre>
 *
 * <p>
 * The next example is useful in situations where you wish to process data
 * as it is ready on the <i>Event Dispatch Thread</i>.
 *
 * <p>
 * Now we want to find the first N prime numbers and display the results in a
 * {@code JTextArea}.  While this is computing, we want to update our
 * progress in a {@code JProgressBar}.  Finally, we also want to print
 * the prime numbers to {@code System.out}.
 * <pre>
 * class PrimeNumbersTask extends
 *         SwingWorker&lt;List&lt;Integer&gt;, Integer&gt; {
 *     PrimeNumbersTask(JTextArea textArea, int numbersToFind) {
 *         //initialize
 *     }
 *
 *     {@code @Override}
 *     public List&lt;Integer&gt; doInBackground() {
 *         while (! enough &amp;&amp; ! isCancelled()) {
 *                 number = nextPrimeNumber();
 *                 publish(number);
 *                 setProgress(100 * numbers.size() / numbersToFind);
 *             }
 *         }
 *         return numbers;
 *     }
 *
 *     {@code @Override}
 *     protected void process(List&lt;Integer&gt; chunks) {
 *         for (int number : chunks) {
 *             textArea.append(number + &quot;\n&quot;);
 *         }
 *     }
 * }
 *
 * JTextArea textArea = new JTextArea();
 * final JProgressBar progressBar = new JProgressBar(0, 100);
 * PrimeNumbersTask task = new PrimeNumbersTask(textArea, N);
 * task.addPropertyChangeListener(
 *     new PropertyChangeListener() {
 *         public  void propertyChange(PropertyChangeEvent evt) {
 *             if (&quot;progress&quot;.equals(evt.getPropertyName())) {
 *                 progressBar.setValue((Integer)evt.getNewValue());
 *             }
 *         }
 *     });
 *
 * task.execute();
 * System.out.println(task.get()); //prints all prime numbers we have got
 * </pre>
 *
 * <p>
 * Because {@code SwingWorker} implements {@code Runnable}, a
 * {@code SwingWorker} can be submitted to an
 * {@link java.util.concurrent.Executor} for execution.
 *
 * @author Igor Kushnirskiy
 *
 * @param <T> the result type returned by this {@code SwingWorker's}
 *        {@code doInBackground} and {@code get} methods
 * @param <V> the type used for carrying out intermediate results by this
 *        {@code SwingWorker's} {@code publish} and {@code process} methods
 *
 * @since 1.6
 */
public abstract class SwingWorker<T, V> implements RunnableFuture<T> {
    number of worker threads.
/**
     * number of worker threads.
     */
    private static final int MAX_WORKER_THREADS = 10;

    current progress.
/**
     * current progress.
     */
    private volatile int progress;

    current state.
/**
     * current state.
     */
    private volatile StateValue state;

    everything is run inside this FutureTask. Also it is used as
a delegatee for the Future API.
/**
     * everything is run inside this FutureTask. Also it is used as
     * a delegatee for the Future API.
     */
    private final FutureTask<T> future;

    all propertyChangeSupport goes through this.
/**
     * all propertyChangeSupport goes through this.
     */
    private final PropertyChangeSupport propertyChangeSupport;

    handler for process mehtod. /**
     * handler for {@code process} mehtod.
     */
    private AccumulativeRunnable<V> doProcess;

    handler for progress property change notifications.
/**
     * handler for progress property change notifications.
     */
    private AccumulativeRunnable<Integer> doNotifyProgressChange;

    private final AccumulativeRunnable<Runnable> doSubmit = getDoSubmit();

    Values for the state bound property. 
Since: 1.6/**
     * Values for the {@code state} bound property.
     * @since 1.6
     */
    public enum StateValue {
        Initial SwingWorker state. /**
         * Initial {@code SwingWorker} state.
         */
        PENDING,
        SwingWorker is STARTED before invoking doInBackground. /**
         * {@code SwingWorker} is {@code STARTED}
         * before invoking {@code doInBackground}.
         */
        STARTED,

        SwingWorker is DONE after doInBackground method is finished. /**
         * {@code SwingWorker} is {@code DONE}
         * after {@code doInBackground} method
         * is finished.
         */
        DONE
    };

    Constructs this SwingWorker. /**
     * Constructs this {@code SwingWorker}.
     */
    public SwingWorker() {
        Callable<T> callable =
                new Callable<T>() {
                    public T call() throws Exception {
                        setState(StateValue.STARTED);
                        return doInBackground();
                    }
                };

        future = new FutureTask<T>(callable) {
                       @Override
                       protected void done() {
                           doneEDT();
                           setState(StateValue.DONE);
                       }
                   };

       state = StateValue.PENDING;
       propertyChangeSupport = new SwingWorkerPropertyChangeSupport(this);
       doProcess = null;
       doNotifyProgressChange = null;
    }

    Computes a result, or throws an exception if unable to do so.

Note that this method is executed only once.

Note: this method is executed in a background thread.
Throws: Exception – if unable to compute a result
Returns: the computed result/**
     * Computes a result, or throws an exception if unable to do so.
     *
     * <p>
     * Note that this method is executed only once.
     *
     * <p>
     * Note: this method is executed in a background thread.
     *
     *
     * @return the computed result
     * @throws Exception if unable to compute a result
     *
     */
    protected abstract T doInBackground() throws Exception ;

    Sets this Future to the result of computation unless it has been cancelled. /**
     * Sets this {@code Future} to the result of computation unless
     * it has been cancelled.
     */
    public final void run() {
        future.run();
    }

    Sends data chunks to the process method. This method is to be used from inside the doInBackground method to deliver intermediate results for processing on the Event Dispatch Thread inside the process method.  Because the process method is invoked asynchronously on the Event Dispatch Thread multiple invocations to the publish method might occur before the process method is executed. For performance purposes all these invocations are coalesced into one invocation with concatenated arguments. 

For example:
publish("1");
publish("2", "3");
publish("4", "5", "6");

might result in:
process("1", "2", "3", "4", "5", "6")


Sample Usage. This code snippet loads some tabular data and updates DefaultTableModel with it. Note that it safe to mutate the tableModel from inside the process method because it is invoked on the Event Dispatch Thread.
class TableSwingWorker extends SwingWorker<DefaultTableModel, Object[]> { private final DefaultTableModel tableModel; public TableSwingWorker(DefaultTableModel tableModel) { this.tableModel = tableModel; } @Override protected DefaultTableModel doInBackground() throws Exception { for (Object[] row = loadData(); ! isCancelled() && row != null; row = loadData()) { publish((Object[]) row); } return tableModel; } @Override protected void process(List<Object[]> chunks) { for (Object[] row : chunks) { tableModel.addRow(row); } } } 
Params: chunks – intermediate results to process
See Also: process/**
     * Sends data chunks to the {@link #process} method. This method is to be
     * used from inside the {@code doInBackground} method to deliver
     * intermediate results
     * for processing on the <i>Event Dispatch Thread</i> inside the
     * {@code process} method.
     *
     * <p>
     * Because the {@code process} method is invoked asynchronously on
     * the <i>Event Dispatch Thread</i>
     * multiple invocations to the {@code publish} method
     * might occur before the {@code process} method is executed. For
     * performance purposes all these invocations are coalesced into one
     * invocation with concatenated arguments.
     *
     * <p>
     * For example:
     *
     * <pre>
     * publish(&quot;1&quot;);
     * publish(&quot;2&quot;, &quot;3&quot;);
     * publish(&quot;4&quot;, &quot;5&quot;, &quot;6&quot;);
     * </pre>
     *
     * might result in:
     *
     * <pre>
     * process(&quot;1&quot;, &quot;2&quot;, &quot;3&quot;, &quot;4&quot;, &quot;5&quot;, &quot;6&quot;)
     * </pre>
     *
     * <p>
     * <b>Sample Usage</b>. This code snippet loads some tabular data and
     * updates {@code DefaultTableModel} with it. Note that it safe to mutate
     * the tableModel from inside the {@code process} method because it is
     * invoked on the <i>Event Dispatch Thread</i>.
     *
     * <pre>
     * class TableSwingWorker extends
     *         SwingWorker&lt;DefaultTableModel, Object[]&gt; {
     *     private final DefaultTableModel tableModel;
     *
     *     public TableSwingWorker(DefaultTableModel tableModel) {
     *         this.tableModel = tableModel;
     *     }
     *
     *     {@code @Override}
     *     protected DefaultTableModel doInBackground() throws Exception {
     *         for (Object[] row = loadData();
     *                  ! isCancelled() &amp;&amp; row != null;
     *                  row = loadData()) {
     *             publish((Object[]) row);
     *         }
     *         return tableModel;
     *     }
     *
     *     {@code @Override}
     *     protected void process(List&lt;Object[]&gt; chunks) {
     *         for (Object[] row : chunks) {
     *             tableModel.addRow(row);
     *         }
     *     }
     * }
     * </pre>
     *
     * @param chunks intermediate results to process
     *
     * @see #process
     *
     */
    protected final void publish(V... chunks) {
        synchronized (this) {
            if (doProcess == null) {
                doProcess = new AccumulativeRunnable<V>() {
                    @Override
                    public void run(List<V> args) {
                        process(args);
                    }
                    @Override
                    protected void submit() {
                        doSubmit.add(this);
                    }
                };
            }
        }
        doProcess.add(chunks);
    }

    Receives data chunks from the publish method asynchronously on the Event Dispatch Thread.
 Please refer to the publish method for more details. 
Params: chunks – intermediate results to process
See Also: publish/**
     * Receives data chunks from the {@code publish} method asynchronously on the
     * <i>Event Dispatch Thread</i>.
     *
     * <p>
     * Please refer to the {@link #publish} method for more details.
     *
     * @param chunks intermediate results to process
     *
     * @see #publish
     *
     */
    protected void process(List<V> chunks) {
    }

    Executed on the Event Dispatch Thread after the doInBackground method is finished. The default implementation does nothing. Subclasses may override this method to perform completion actions on the Event Dispatch Thread. Note
that you can query status inside the implementation of this method to
determine the result of this task or whether this task has been cancelled.
See Also: doInBackground
isCancelled()
get/**
     * Executed on the <i>Event Dispatch Thread</i> after the {@code doInBackground}
     * method is finished. The default
     * implementation does nothing. Subclasses may override this method to
     * perform completion actions on the <i>Event Dispatch Thread</i>. Note
     * that you can query status inside the implementation of this method to
     * determine the result of this task or whether this task has been cancelled.
     *
     * @see #doInBackground
     * @see #isCancelled()
     * @see #get
     */
    protected void done() {
    }

    Sets the progress bound property. The value should be from 0 to 100.  Because PropertyChangeListeners are notified asynchronously on the Event Dispatch Thread multiple invocations to the setProgress method might occur before any PropertyChangeListeners are invoked. For performance purposes all these invocations are coalesced into one invocation with the last invocation argument only. 

For example, the following invokations:
setProgress(1);
setProgress(2);
setProgress(3);
 might result in a single PropertyChangeListener notification with the value 3. 
Params: progress – the progress value to set
Throws: IllegalArgumentException – is value not from 0 to 100/**
     * Sets the {@code progress} bound property.
     * The value should be from 0 to 100.
     *
     * <p>
     * Because {@code PropertyChangeListener}s are notified asynchronously on
     * the <i>Event Dispatch Thread</i> multiple invocations to the
     * {@code setProgress} method might occur before any
     * {@code PropertyChangeListeners} are invoked. For performance purposes
     * all these invocations are coalesced into one invocation with the last
     * invocation argument only.
     *
     * <p>
     * For example, the following invokations:
     *
     * <pre>
     * setProgress(1);
     * setProgress(2);
     * setProgress(3);
     * </pre>
     *
     * might result in a single {@code PropertyChangeListener} notification with
     * the value {@code 3}.
     *
     * @param progress the progress value to set
     * @throws IllegalArgumentException is value not from 0 to 100
     */
    protected final void setProgress(int progress) {
        if (progress < 0 || progress > 100) {
            throw new IllegalArgumentException("the value should be from 0 to 100");
        }
        if (this.progress == progress) {
            return;
        }
        int oldProgress = this.progress;
        this.progress = progress;
        if (! getPropertyChangeSupport().hasListeners("progress")) {
            return;
        }
        synchronized (this) {
            if (doNotifyProgressChange == null) {
                doNotifyProgressChange =
                    new AccumulativeRunnable<Integer>() {
                        @Override
                        public void run(List<Integer> args) {
                            firePropertyChange("progress",
                               args.get(0),
                               args.get(args.size() - 1));
                        }
                        @Override
                        protected void submit() {
                            doSubmit.add(this);
                        }
                    };
            }
        }
        doNotifyProgressChange.add(oldProgress, progress);
    }

    Returns the progress bound property. 
Returns: the progress bound property./**
     * Returns the {@code progress} bound property.
     *
     * @return the progress bound property.
     */
    public final int getProgress() {
        return progress;
    }

    Schedules this SwingWorker for execution on a worker
thread. There are a number of worker threads available. In the
event all worker threads are busy handling other SwingWorkers this SwingWorker is placed in a waiting queue.  Note: SwingWorker is only designed to be executed once. Executing a SwingWorker more than once will not result in invoking the doInBackground method twice. /**
     * Schedules this {@code SwingWorker} for execution on a <i>worker</i>
     * thread. There are a number of <i>worker</i> threads available. In the
     * event all <i>worker</i> threads are busy handling other
     * {@code SwingWorkers} this {@code SwingWorker} is placed in a waiting
     * queue.
     *
     * <p>
     * Note:
     * {@code SwingWorker} is only designed to be executed once.  Executing a
     * {@code SwingWorker} more than once will not result in invoking the
     * {@code doInBackground} method twice.
     */
    public final void execute() {
        getWorkersExecutorService().execute(this);
    }

    // Future methods START
    {@inheritDoc}
/**
     * {@inheritDoc}
     */
    public final boolean cancel(boolean mayInterruptIfRunning) {
        return future.cancel(mayInterruptIfRunning);
    }

    {@inheritDoc}
/**
     * {@inheritDoc}
     */
    public final boolean isCancelled() {
        return future.isCancelled();
    }

    {@inheritDoc}
/**
     * {@inheritDoc}
     */
    public final boolean isDone() {
        return future.isDone();
    }

    {@inheritDoc}
 Note: calling get on the Event Dispatch Thread blocks
all events, including repaints, from being processed until this SwingWorker is complete. 
 When you want the SwingWorker to block on the Event
Dispatch Thread we recommend that you use a modal dialog.

For example:
class SwingWorkerCompletionWaiter extends PropertyChangeListener {
    private JDialog dialog;
    public SwingWorkerCompletionWaiter(JDialog dialog) {
        this.dialog = dialog;
    }
    public void propertyChange(PropertyChangeEvent event) {
        if ("state".equals(event.getPropertyName())
                && SwingWorker.StateValue.DONE == event.getNewValue()) {
            dialog.setVisible(false);
            dialog.dispose();
        }
    }
}
JDialog dialog = new JDialog(owner, true);
swingWorker.addPropertyChangeListener(
    new SwingWorkerCompletionWaiter(dialog));
swingWorker.execute();
//the dialog will be visible until the SwingWorker is done
dialog.setVisible(true);

/**
     * {@inheritDoc}
     * <p>
     * Note: calling {@code get} on the <i>Event Dispatch Thread</i> blocks
     * <i>all</i> events, including repaints, from being processed until this
     * {@code SwingWorker} is complete.
     *
     * <p>
     * When you want the {@code SwingWorker} to block on the <i>Event
     * Dispatch Thread</i> we recommend that you use a <i>modal dialog</i>.
     *
     * <p>
     * For example:
     *
     * <pre>
     * class SwingWorkerCompletionWaiter extends PropertyChangeListener {
     *     private JDialog dialog;
     *
     *     public SwingWorkerCompletionWaiter(JDialog dialog) {
     *         this.dialog = dialog;
     *     }
     *
     *     public void propertyChange(PropertyChangeEvent event) {
     *         if (&quot;state&quot;.equals(event.getPropertyName())
     *                 &amp;&amp; SwingWorker.StateValue.DONE == event.getNewValue()) {
     *             dialog.setVisible(false);
     *             dialog.dispose();
     *         }
     *     }
     * }
     * JDialog dialog = new JDialog(owner, true);
     * swingWorker.addPropertyChangeListener(
     *     new SwingWorkerCompletionWaiter(dialog));
     * swingWorker.execute();
     * //the dialog will be visible until the SwingWorker is done
     * dialog.setVisible(true);
     * </pre>
     */
    public final T get() throws InterruptedException, ExecutionException {
        return future.get();
    }

    {@inheritDoc}
 Please refer to get for more details. /**
     * {@inheritDoc}
     * <p>
     * Please refer to {@link #get} for more details.
     */
    public final T get(long timeout, TimeUnit unit) throws InterruptedException,
            ExecutionException, TimeoutException {
        return future.get(timeout, unit);
    }

    // Future methods END

    // PropertyChangeSupports methods START
    Adds a PropertyChangeListener to the listener list. The listener is registered for all properties. The same listener object may be added more than once, and will be called as many times as it is added. If listener is null, no exception is thrown and no action is taken.  Note: This is merely a convenience wrapper. All work is delegated to PropertyChangeSupport from getPropertyChangeSupport. 
Params: listener – the PropertyChangeListener to be added/**
     * Adds a {@code PropertyChangeListener} to the listener list. The listener
     * is registered for all properties. The same listener object may be added
     * more than once, and will be called as many times as it is added. If
     * {@code listener} is {@code null}, no exception is thrown and no action is taken.
     *
     * <p>
     * Note: This is merely a convenience wrapper. All work is delegated to
     * {@code PropertyChangeSupport} from {@link #getPropertyChangeSupport}.
     *
     * @param listener the {@code PropertyChangeListener} to be added
     */
    public final void addPropertyChangeListener(PropertyChangeListener listener) {
        getPropertyChangeSupport().addPropertyChangeListener(listener);
    }

    Removes a PropertyChangeListener from the listener list. This removes a PropertyChangeListener that was registered for all properties. If listener was added more than once to the same event source, it will be notified one less time after being removed. If listener is null, or was never added, no exception is thrown and no action is taken.  Note: This is merely a convenience wrapper. All work is delegated to PropertyChangeSupport from getPropertyChangeSupport. 
Params: listener – the PropertyChangeListener to be removed/**
     * Removes a {@code PropertyChangeListener} from the listener list. This
     * removes a {@code PropertyChangeListener} that was registered for all
     * properties. If {@code listener} was added more than once to the same
     * event source, it will be notified one less time after being removed. If
     * {@code listener} is {@code null}, or was never added, no exception is
     * thrown and no action is taken.
     *
     * <p>
     * Note: This is merely a convenience wrapper. All work is delegated to
     * {@code PropertyChangeSupport} from {@link #getPropertyChangeSupport}.
     *
     * @param listener the {@code PropertyChangeListener} to be removed
     */
    public final void removePropertyChangeListener(PropertyChangeListener listener) {
        getPropertyChangeSupport().removePropertyChangeListener(listener);
    }

    Reports a bound property update to any registered listeners. No event is fired if old and new are equal and non-null.  This SwingWorker will be the source for any generated events. 

When called off the Event Dispatch Thread PropertyChangeListeners are notified asynchronously on the Event Dispatch Thread.
 Note: This is merely a convenience wrapper. All work is delegated to PropertyChangeSupport from getPropertyChangeSupport. 
Params: propertyName – the programmatic name of the property that was
       changed
oldValue – the old value of the property
newValue – the new value of the property/**
     * Reports a bound property update to any registered listeners. No event is
     * fired if {@code old} and {@code new} are equal and non-null.
     *
     * <p>
     * This {@code SwingWorker} will be the source for
     * any generated events.
     *
     * <p>
     * When called off the <i>Event Dispatch Thread</i>
     * {@code PropertyChangeListeners} are notified asynchronously on
     * the <i>Event Dispatch Thread</i>.
     * <p>
     * Note: This is merely a convenience wrapper. All work is delegated to
     * {@code PropertyChangeSupport} from {@link #getPropertyChangeSupport}.
     *
     *
     * @param propertyName the programmatic name of the property that was
     *        changed
     * @param oldValue the old value of the property
     * @param newValue the new value of the property
     */
    public final void firePropertyChange(String propertyName, Object oldValue,
            Object newValue) {
        getPropertyChangeSupport().firePropertyChange(propertyName,
            oldValue, newValue);
    }

    Returns the PropertyChangeSupport for this SwingWorker. This method is used when flexible access to bound properties support is needed.  This SwingWorker will be the source for any generated events. 
 Note: The returned PropertyChangeSupport notifies any PropertyChangeListeners asynchronously on the Event Dispatch
Thread in the event that firePropertyChange or fireIndexedPropertyChange are called off the Event Dispatch
Thread.
Returns: PropertyChangeSupport for this SwingWorker/**
     * Returns the {@code PropertyChangeSupport} for this {@code SwingWorker}.
     * This method is used when flexible access to bound properties support is
     * needed.
     * <p>
     * This {@code SwingWorker} will be the source for
     * any generated events.
     *
     * <p>
     * Note: The returned {@code PropertyChangeSupport} notifies any
     * {@code PropertyChangeListener}s asynchronously on the <i>Event Dispatch
     * Thread</i> in the event that {@code firePropertyChange} or
     * {@code fireIndexedPropertyChange} are called off the <i>Event Dispatch
     * Thread</i>.
     *
     * @return {@code PropertyChangeSupport} for this {@code SwingWorker}
     */
    public final PropertyChangeSupport getPropertyChangeSupport() {
        return propertyChangeSupport;
    }

    // PropertyChangeSupports methods END

    Returns the SwingWorker state bound property. 
Returns: the current state/**
     * Returns the {@code SwingWorker} state bound property.
     *
     * @return the current state
     */
    public final StateValue getState() {
        /*
         * DONE is a speacial case
         * to keep getState and isDone is sync
         */
        if (isDone()) {
            return StateValue.DONE;
        } else {
            return state;
        }
    }

    Sets this SwingWorker state bound property. 
Params: the – state state to set/**
     * Sets this {@code SwingWorker} state bound property.
     * @param the state state to set
     */
    private void setState(StateValue state) {
        StateValue old = this.state;
        this.state = state;
        firePropertyChange("state", old, state);
    }

    Invokes done on the EDT. /**
     * Invokes {@code done} on the EDT.
     */
    private void doneEDT() {
        Runnable doDone =
            new Runnable() {
                public void run() {
                    done();
                }
            };
        if (SwingUtilities.isEventDispatchThread()) {
            doDone.run();
        } else {
            doSubmit.add(doDone);
        }
    }


    returns workersExecutorService.
returns the service stored in the appContext or creates it if
necessary. If the last one it triggers autoShutdown thread to
get started.
See Also: startAutoShutdownThread
Returns: ExecutorService for the SwingWorkers/**
     * returns workersExecutorService.
     *
     * returns the service stored in the appContext or creates it if
     * necessary. If the last one it triggers autoShutdown thread to
     * get started.
     *
     * @return ExecutorService for the {@code SwingWorkers}
     * @see #startAutoShutdownThread
     */
    private static synchronized ExecutorService getWorkersExecutorService() {
        final AppContext appContext = AppContext.getAppContext();
        Object obj = appContext.get(SwingWorker.class);
        if (obj == null) {
            //this creates non-daemon threads.
            ThreadFactory threadFactory =
                new ThreadFactory() {
                    final ThreadFactory defaultFactory =
                        Executors.defaultThreadFactory();
                    public Thread newThread(final Runnable r) {
                        Thread thread =
                            defaultFactory.newThread(r);
                        thread.setName("SwingWorker-"
                            + thread.getName());
                        return thread;
                    }
                };

            /*
             * We want a to have no more than MAX_WORKER_THREADS
             * running threads.
             *
             * We want a worker thread to wait no longer than 1 second
             * for new tasks before terminating.
             */
            obj = new ThreadPoolExecutor(0, MAX_WORKER_THREADS,
                                         1L, TimeUnit.SECONDS,
                                         new LinkedBlockingQueue<Runnable>(),
                                         threadFactory) {

                    private final ReentrantLock pauseLock = new ReentrantLock();
                    private final Condition unpaused = pauseLock.newCondition();
                    private boolean isPaused = false;
                    private final ReentrantLock executeLock = new ReentrantLock();

                    @Override
                    public void execute(Runnable command) {
                        /*
                         * ThreadPoolExecutor first tries to run task
                         * in a corePool. If all threads are busy it
                         * tries to add task to the waiting queue. If it
                         * fails it run task in maximumPool.
                         *
                         * We want corePool to be 0 and
                         * maximumPool to be MAX_WORKER_THREADS
                         * We need to change the order of the execution.
                         * First try corePool then try maximumPool
                         * pool and only then store to the waiting
                         * queue. We can not do that because we would
                         * need access to the private methods.
                         *
                         * Instead we enlarge corePool to
                         * MAX_WORKER_THREADS before the execution and
                         * shrink it back to 0 after.
                         * It does pretty much what we need.
                         *
                         * While we changing the corePoolSize we need
                         * to stop running worker threads from accepting new
                         * tasks.
                         */

                        //we need atomicity for the execute method.
                        executeLock.lock();
                        try {

                            pauseLock.lock();
                            try {
                                isPaused = true;
                            } finally {
                                pauseLock.unlock();
                            }

                            setCorePoolSize(MAX_WORKER_THREADS);
                            super.execute(command);
                            setCorePoolSize(0);

                            pauseLock.lock();
                            try {
                                isPaused = false;
                                unpaused.signalAll();
                            } finally {
                                pauseLock.unlock();
                            }
                        } finally {
                            executeLock.unlock();
                        }
                    }
                    @Override
                    protected void afterExecute(Runnable r, Throwable t) {
                        super.afterExecute(r, t);
                        pauseLock.lock();
                        try {
                            while(isPaused) {
                                unpaused.await();
                            }
                        } catch(InterruptedException ignore) {

                        } finally {
                            pauseLock.unlock();
                        }
                    }
                };
            appContext.put(SwingWorker.class, obj);

            // Don't use ShutdownHook here as it's not enough. We should track
            // AppContext disposal instead of JVM shutdown, see 6799345 for details
            final ExecutorService es = (ExecutorService) obj;
            appContext.addPropertyChangeListener(AppContext.DISPOSED_PROPERTY_NAME,
                new PropertyChangeListener() {
                    public void propertyChange(PropertyChangeEvent pce) {
                        boolean disposed = (Boolean)pce.getNewValue();
                        if (disposed) {
                            final WeakReference<ExecutorService> executorServiceRef =
                                new WeakReference<ExecutorService>(es);
                            final ExecutorService executorService =
                                executorServiceRef.get();
                            if (executorService != null) {
                                AccessController.doPrivileged(
                                    new PrivilegedAction<Void>() {
                                        public Void run() {
                                            executorService.shutdown();
                                            return null;
                                        }
				    }
				);
			    }
			}
		    }
		}
	    );		 
        }
        return (ExecutorService)obj;
    }

    private static final Object DO_SUBMIT_KEY = new Object(); // doSubmit
    private static AccumulativeRunnable<Runnable> getDoSubmit() {
        synchronized (DO_SUBMIT_KEY) {
            final AppContext appContext = AppContext.getAppContext();
            Object doSubmit = appContext.get(DO_SUBMIT_KEY);
            if (doSubmit == null) {
                doSubmit = new DoSubmitAccumulativeRunnable();
                appContext.put(DO_SUBMIT_KEY, doSubmit);
            }
            return (AccumulativeRunnable<Runnable>) doSubmit;
        }
    }
    private static class DoSubmitAccumulativeRunnable
          extends AccumulativeRunnable<Runnable> implements ActionListener {
        private final static int DELAY = (int) (1000 / 30);
        @Override
        protected void run(List<Runnable> args) {
            for (Runnable runnable : args) {
                runnable.run();
            }
        }
        @Override
        protected void submit() {
            Timer timer = new Timer(DELAY, this);
            timer.setRepeats(false);
            timer.start();
        }
        public void actionPerformed(ActionEvent event) {
            run();
        }
    }

    private class SwingWorkerPropertyChangeSupport
            extends PropertyChangeSupport {
        SwingWorkerPropertyChangeSupport(Object source) {
            super(source);
        }
        @Override
        public void firePropertyChange(final PropertyChangeEvent evt) {
            if (SwingUtilities.isEventDispatchThread()) {
                super.firePropertyChange(evt);
            } else {
                doSubmit.add(
                    new Runnable() {
                        public void run() {
                            SwingWorkerPropertyChangeSupport.this
                                .firePropertyChange(evt);
                        }
                    });
            }
        }
    }
}
Author:	Igor Kushnirskiy
Type parameters:	<T> – the result type returned by this `SwingWorker's` `doInBackground` and `get` methods <V> – the type used for carrying out intermediate results by this `SwingWorker's` `publish` and `process` methods
Since:	1.6
Throws:	Exception – if unable to compute a result
Returns:	the computed result
Params:	chunks – intermediate results to process
See Also:	process
Params:	progress – the progress value to set
Throws:	IllegalArgumentException – is value not from 0 to 100
See Also:	startAutoShutdownThread
Returns:	ExecutorService for the `SwingWorkers`
/

java/ 6/ javax/swing/SwingWorker.java
