src/java.desktop/share/classes/javax/swing/SwingWorker.java

/*
 * Copyright (c) 2005, 2024, 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.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.lang.ref.WeakReference;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.RunnableFuture;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

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

/**
 * An abstract class to perform lengthy GUI-interaction tasks in a
 * background thread. Several background threads can be used to execute such
 * tasks. However, the exact strategy of choosing a thread for any particular
 * {@code SwingWorker} is unspecified and should not be relied on.
 * <p>
 * When writing a multi-threaded application using Swing, there are
 * two constraints to keep in mind:
 * (refer to
 * <a href="https://docs.oracle.com/javase/tutorial/uiswing/concurrency/index.html">
 *   Concurrency in Swing
 * </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>
 * 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.
     */
    private static final int MAX_WORKER_THREADS = 10;

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

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

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

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

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

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

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

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

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

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

       future = new FutureTask<T>(callable);

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

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

    /**
     * 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
     *
     */
    @SafeVarargs
    @SuppressWarnings("varargs") // Passing chunks to add is safe
    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 {@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 <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 {@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 invocations:
     *
     * <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 {@code progress} bound property.
     *
     * @return the progress bound property.
     */
    public final int getProgress() {
        return progress;
    }

    /**
     * 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}
     */
    public final boolean cancel(boolean mayInterruptIfRunning) {
        return future.cancel(mayInterruptIfRunning);
    }

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

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

    /**
     * {@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 implements 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>
     *
     * @throws CancellationException {@inheritDoc}
     */
    public final T get() throws InterruptedException, ExecutionException {
        return future.get();
    }

    /**
     * {@inheritDoc}
     * <p>
     * Please refer to {@link #get} for more details.
     *
     * @throws CancellationException {@inheritDoc}
     */
    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 {@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 {@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 {@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 {@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 {@code SwingWorker} state bound property.
     *
     * @return the current state
     */
    public final StateValue getState() {
        /*
         * DONE is a special case
         * to keep getState and isDone is sync
         */
        if (isDone()) {
            return StateValue.DONE;
        } else {
            return state;
        }
    }

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

    /**
     * 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.
     *
     * @return ExecutorService for the {@code SwingWorkers}
     */
    private static synchronized ExecutorService getWorkersExecutorService() {
        final AppContext appContext = AppContext.getAppContext();
        ExecutorService executorService =
            (ExecutorService) appContext.get(SwingWorker.class);
        if (executorService == null) {
            //this creates 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());
                        thread.setDaemon(true);
                        return thread;
                    }
                };

            executorService =
                new ThreadPoolExecutor(MAX_WORKER_THREADS, MAX_WORKER_THREADS,
                                       10L, TimeUnit.MINUTES,
                                       new LinkedBlockingQueue<Runnable>(),
                                       threadFactory);
            appContext.put(SwingWorker.class, executorService);

            // 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;
            appContext.addPropertyChangeListener(AppContext.DISPOSED_PROPERTY_NAME,
                new PropertyChangeListener() {
                    @Override
                    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) {
                                executorService.shutdown();
                            }
                        }
                    }
                }
            );
        }
        return executorService;
    }

    private static final Object DO_SUBMIT_KEY = new StringBuilder("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);
            }
            @SuppressWarnings("unchecked")
            AccumulativeRunnable<Runnable> tmp = (AccumulativeRunnable<Runnable>) doSubmit;
            return tmp;
        }
    }
    private static class DoSubmitAccumulativeRunnable
          extends AccumulativeRunnable<Runnable> implements ActionListener {
        private static final int DELAY = 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();
        }
    }

    @SuppressWarnings("serial") // JDK-implementation class
    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);
                        }
                    });
            }
        }
    }
}