Java tutorial
/* =========================================================== * JFreeChart : a free chart library for the Java(tm) platform * =========================================================== * * (C) Copyright 2000-2013, by Object Refinery Limited and Contributors. * * Project Info: http://www.jfree.org/jfreechart/index.html * * This library is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation; either version 2.1 of the License, or * (at your option) any later version. * * This library 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 Lesser General Public * License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, * USA. * * [Oracle and Java are registered trademarks of Oracle and/or its affiliates. * Other names may be trademarks of their respective owners.] * * -------------------- * AbstractDataset.java * -------------------- * (C)opyright 2000-2013, by Object Refinery Limited. * * Original Author: David Gilbert (for Object Refinery Limited); * Contributor(s): Nicolas Brodu (for Astrium and EADS Corporate Research * Center); * * Changes (from 21-Aug-2001) * -------------------------- * 21-Aug-2001 : Added standard header. Fixed DOS encoding problem (DG); * 18-Sep-2001 : Updated e-mail address in header (DG); * 15-Oct-2001 : Moved to new package (com.jrefinery.data.*) (DG); * 22-Oct-2001 : Renamed DataSource.java --> Dataset.java etc. (DG); * 17-Nov-2001 : Changed constructor from public to protected, created new * AbstractSeriesDataset class and transferred series-related * methods, updated Javadoc comments (DG); * 04-Mar-2002 : Updated import statements (DG); * 11-Jun-2002 : Updated for change in the event constructor (DG); * 07-Aug-2002 : Changed listener list to use * javax.swing.event.EventListenerList (DG); * 04-Oct-2002 : Fixed errors reported by Checkstyle (DG); * 27-Mar-2003 : Implemented Serializable (DG); * 18-Aug-2003 : Implemented Cloneable (DG); * 08-Sep-2003 : Serialization fixes (NB); * 11-Sep-2003 : Cloning Fixes (NB); * 01-Jun-2005 : Added hasListener() method for unit testing (DG); * 03-Jul-2013 : Use ParamChecks (DG); * 21-Nov-2013 : Added notify flag to allow suppressing change events * temporarily (DG); * */ package org.jfree.data.general; import java.io.IOException; import java.io.InvalidObjectException; import java.io.ObjectInputStream; import java.io.ObjectInputValidation; import java.io.ObjectOutputStream; import java.io.Serializable; import java.util.Arrays; import java.util.EventListener; import java.util.List; import javax.swing.event.EventListenerList; import org.jfree.chart.util.ParamChecks; /** * An abstract implementation of the {@link Dataset} interface, containing a * mechanism for registering change listeners. */ public abstract class AbstractDataset implements Dataset, Cloneable, Serializable, ObjectInputValidation { /** For serialization. */ private static final long serialVersionUID = 1918768939869230744L; /** The group that the dataset belongs to. */ private DatasetGroup group; /** Storage for registered change listeners. */ private transient EventListenerList listenerList; /** * A flag that can be used to temporarily suppress dataset change event * notifications. */ private boolean notify; /** * Constructs a dataset. By default, the dataset is assigned to its own * group. */ protected AbstractDataset() { this.group = new DatasetGroup(); this.listenerList = new EventListenerList(); this.notify = true; } /** * Returns the dataset group for the dataset. * * @return The group (never <code>null</code>). * * @see #setGroup(DatasetGroup) */ @Override public DatasetGroup getGroup() { return this.group; } /** * Sets the dataset group for the dataset. * * @param group the group (<code>null</code> not permitted). * * @see #getGroup() */ @Override public void setGroup(DatasetGroup group) { ParamChecks.nullNotPermitted(group, "group"); this.group = group; } /** * Returns the value of the notify flag. The default value is * <code>true</code>. If this is <code>false</code>, calls to the * {@link #fireDatasetChanged()} method will NOT trigger a dataset * change event. * * @return A boolean. * * @since 1.0.17 */ public boolean getNotify() { return this.notify; } /** * Sets the notify flag, which controls whether or not the {@link #fireDatasetChanged()} * method notifies listeners. Setting this flag to <code>true</code> will * trigger a <code>DatasetChangeEvent</code> because there may be * queued up changes. * * @param notify the new flag value. * * @since 1.0.17 */ public void setNotify(boolean notify) { this.notify = notify; if (notify) { fireDatasetChanged(); } } /** * Registers an object to receive notification of changes to the dataset. * * @param listener the object to register. * * @see #removeChangeListener(DatasetChangeListener) */ @Override public void addChangeListener(DatasetChangeListener listener) { this.listenerList.add(DatasetChangeListener.class, listener); } /** * Deregisters an object so that it no longer receives notification of * changes to the dataset. * * @param listener the object to deregister. * * @see #addChangeListener(DatasetChangeListener) */ @Override public void removeChangeListener(DatasetChangeListener listener) { this.listenerList.remove(DatasetChangeListener.class, listener); } /** * Returns <code>true</code> if the specified object is registered with * the dataset as a listener. Most applications won't need to call this * method, it exists mainly for use by unit testing code. * * @param listener the listener. * * @return A boolean. * * @see #addChangeListener(DatasetChangeListener) * @see #removeChangeListener(DatasetChangeListener) */ public boolean hasListener(EventListener listener) { List list = Arrays.asList(this.listenerList.getListenerList()); return list.contains(listener); } /** * Notifies all registered listeners that the dataset has changed, * provided that the <code>notify</code> flag has not been set to * <code>false</code>. * * @see #addChangeListener(DatasetChangeListener) */ protected void fireDatasetChanged() { if (this.notify) { notifyListeners(new DatasetChangeEvent(this, this)); } } /** * Notifies all registered listeners that the dataset has changed. * * @param event contains information about the event that triggered the * notification. * * @see #addChangeListener(DatasetChangeListener) * @see #removeChangeListener(DatasetChangeListener) */ protected void notifyListeners(DatasetChangeEvent event) { Object[] listeners = this.listenerList.getListenerList(); for (int i = listeners.length - 2; i >= 0; i -= 2) { if (listeners[i] == DatasetChangeListener.class) { ((DatasetChangeListener) listeners[i + 1]).datasetChanged(event); } } } /** * Returns a clone of the dataset. The cloned dataset will NOT include the * {@link DatasetChangeListener} references that have been registered with * this dataset. * * @return A clone. * * @throws CloneNotSupportedException if the dataset does not support * cloning. */ @Override public Object clone() throws CloneNotSupportedException { AbstractDataset clone = (AbstractDataset) super.clone(); clone.listenerList = new EventListenerList(); return clone; } /** * Handles serialization. * * @param stream the output stream. * * @throws IOException if there is an I/O problem. */ private void writeObject(ObjectOutputStream stream) throws IOException { stream.defaultWriteObject(); } /** * Restores a serialized object. * * @param stream the input stream. * * @throws IOException if there is an I/O problem. * @throws ClassNotFoundException if there is a problem loading a class. */ private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { stream.defaultReadObject(); this.listenerList = new EventListenerList(); stream.registerValidation(this, 10); // see comments about priority of // 10 in validateObject() } /** * Validates the object. We use this opportunity to call listeners who have * registered during the deserialization process, as listeners are not * serialized. This method is called by the serialization system after the * entire graph is read. * * This object has registered itself to the system with a priority of 10. * Other callbacks may register with a higher priority number to be called * before this object, or with a lower priority number to be called after * the listeners were notified. * * All listeners are supposed to have register by now, either in their * readObject or validateObject methods. Notify them that this dataset has * changed. * * @exception InvalidObjectException If the object cannot validate itself. */ @Override public void validateObject() throws InvalidObjectException { fireDatasetChanged(); } }