jdk/src/java.desktop/share/classes/sun/swing/AccumulativeRunnable.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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 sun.swing;

import java.util.*;
import java.lang.reflect.Array;
import javax.swing.SwingUtilities;

/**
 * An abstract class to be used in the cases where we need {@code Runnable}
 * to perform  some actions on an appendable set of data.
 * The set of data might be appended after the {@code Runnable} is
 * sent for the execution. Usually such {@code Runnables} are sent to
 * the EDT.
 *
 * <p>
 * Usage example:
 *
 * <p>
 * Say we want to implement JLabel.setText(String text) which sends
 * {@code text} string to the JLabel.setTextImpl(String text) on the EDT.
 * In the event JLabel.setText is called rapidly many times off the EDT
 * we will get many updates on the EDT but only the last one is important.
 * (Every next updates overrides the previous one.)
 * We might want to implement this {@code setText} in a way that only
 * the last update is delivered.
 * <p>
 * Here is how one can do this using {@code AccumulativeRunnable}:
 * <pre>
 * {@code AccumulativeRunnable<String> doSetTextImpl =
 *  new  AccumulativeRunnable<String>()} {
 *    {@literal @Override}
 *    {@code protected void run(List<String> args)} {
 *         //set to the last string being passed
 *         setTextImpl(args.get(args.size() - 1));
 *     }
 * }
 * void setText(String text) {
 *     //add text and send for the execution if needed.
 *     doSetTextImpl.add(text);
 * }
 * </pre>
 *
 * <p>
 * Say we want to implement addDirtyRegion(Rectangle rect)
 * which sends this region to the
 * {@code handleDirtyRegions(List<Rect> regiouns)} on the EDT.
 * addDirtyRegions better be accumulated before handling on the EDT.
 *
 * <p>
 * Here is how it can be implemented using AccumulativeRunnable:
 * <pre>
 * {@code AccumulativeRunnable<Rectangle> doHandleDirtyRegions =}
 *    {@code new AccumulativeRunnable<Rectangle>()} {
 *        {@literal @Override}
 *        {@code protected void run(List<Rectangle> args)} {
 *             handleDirtyRegions(args);
 *         }
 *     };
 *  void addDirtyRegion(Rectangle rect) {
 *      doHandleDirtyRegions.add(rect);
 *  }
 * </pre>
 *
 * @author Igor Kushnirskiy
 *
 * @param <T> the type this {@code Runnable} accumulates
 *
 * @since 1.6
 */
public abstract class AccumulativeRunnable<T> implements Runnable {
    private List<T> arguments = null;

    /**
     * Equivalent to {@code Runnable.run} method with the
     * accumulated arguments to process.
     *
     * @param args accumulated argumets to process.
     */
    protected abstract void run(List<T> args);

    /**
     * {@inheritDoc}
     *
     * <p>
     * This implementation calls {@code run(List<T> args)} mehtod
     * with the list of accumulated arguments.
     */
    public final void run() {
        run(flush());
    }

    /**
     * appends arguments and sends this {@code Runnable} for the
     * execution if needed.
     * <p>
     * This implementation uses {@see #submit} to send this
     * {@code Runnable} for execution.
     * @param args the arguments to accumulate
     */
    @SafeVarargs
    @SuppressWarnings("varargs") // Copying args is safe
    public final synchronized void add(T... args) {
        boolean isSubmitted = true;
        if (arguments == null) {
            isSubmitted = false;
            arguments = new ArrayList<T>();
        }
        Collections.addAll(arguments, args);
        if (!isSubmitted) {
            submit();
        }
    }

    /**
     * Sends this {@code Runnable} for the execution
     *
     * <p>
     * This method is to be executed only from {@code add} method.
     *
     * <p>
     * This implementation uses {@code SwingWorker.invokeLater}.
     */
    protected void submit() {
        SwingUtilities.invokeLater(this);
    }

    /**
     * Returns accumulated arguments and flashes the arguments storage.
     *
     * @return accumulated arguments
     */
    private final synchronized List<T> flush() {
        List<T> list = arguments;
        arguments = null;
        return list;
    }
}