001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2007, by Object Refinery Limited and Contributors.
006 *
007 * Project Info:  http://www.jfree.org/jfreechart/index.html
008 *
009 * This library is free software; you can redistribute it and/or modify it 
010 * under the terms of the GNU Lesser General Public License as published by 
011 * the Free Software Foundation; either version 2.1 of the License, or 
012 * (at your option) any later version.
013 *
014 * This library is distributed in the hope that it will be useful, but 
015 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
016 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
017 * License for more details.
018 *
019 * You should have received a copy of the GNU Lesser General Public
020 * License along with this library; if not, write to the Free Software
021 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
022 * USA.  
023 *
024 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
025 * in the United States and other countries.]
026 *
027 * ------------------------
028 * DefaultValueDataset.java
029 * ------------------------
030 * (C) Copyright 2003-2007, by Object Refinery Limited.
031 *
032 * Original Author:  David Gilbert (for Object Refinery Limited);
033 * Contributor(s):   -;
034 *
035 * Changes
036 * -------
037 * 27-Mar-2003 : Version 1 (DG);
038 * 18-Aug-2003 : Implemented Cloneable (DG);
039 * 03-Mar-2005 : Implemented PublicCloneable (DG);
040 * ------------- JFREECHART 1.0.x ---------------------------------------------
041 * 30-Jan-2007 : Added explicit super() call in constructor (for clarity) (DG);
042 * 
043 */
044
045package org.jfree.data.general;
046
047import java.io.Serializable;
048
049import org.jfree.util.ObjectUtilities;
050import org.jfree.util.PublicCloneable;
051
052/**
053 * A dataset that stores a single value (that is possibly <code>null</code>).  
054 * This class provides a default implementation of the {@link ValueDataset} 
055 * interface.
056 */
057public class DefaultValueDataset extends AbstractDataset
058                                 implements ValueDataset, 
059                                            Cloneable, PublicCloneable,
060                                            Serializable {
061
062    /** For serialization. */
063    private static final long serialVersionUID = 8137521217249294891L;
064    
065    /** The value. */
066    private Number value;
067
068    /**
069     * Constructs a new dataset, initially empty.
070     */
071    public DefaultValueDataset() {
072        this(null);
073    }
074    
075    /**
076     * Creates a new dataset with the specified value.
077     * 
078     * @param value  the value.
079     */
080    public DefaultValueDataset(double value) {
081        this(new Double(value));
082    }
083
084    /**
085     * Creates a new dataset with the specified value.
086     *
087     * @param value  the initial value (<code>null</code> permitted).
088     */
089    public DefaultValueDataset(Number value) {
090        super();
091        this.value = value;
092    }
093
094    /**
095     * Returns the value.
096     *
097     * @return The value (possibly <code>null</code>).
098     */
099    public Number getValue() {
100        return this.value;
101    }
102
103    /**
104     * Sets the value and sends a {@link DatasetChangeEvent} to all registered 
105     * listeners.
106     *
107     * @param value  the new value (<code>null</code> permitted).
108     */
109    public void setValue(Number value) {
110        this.value = value;
111        notifyListeners(new DatasetChangeEvent(this, this));
112    }
113
114    /**
115     * Tests this dataset for equality with an arbitrary object.
116     *
117     * @param obj  the object (<code>null</code> permitted).
118     *
119     * @return A boolean.
120     */
121    public boolean equals(Object obj) {
122        if (obj == this) {
123            return true;
124        }
125        if (obj instanceof ValueDataset) {
126            ValueDataset vd = (ValueDataset) obj;
127            return ObjectUtilities.equal(this.value, vd.getValue());
128        }
129        return false;
130    }
131
132    /**
133     * Returns a hash code.
134     * 
135     * @return A hash code.
136     */
137    public int hashCode() {
138        return (this.value != null ? this.value.hashCode() : 0);
139    }
140    
141}