001    /* ===========================================================
002     * JFreeChart : a free chart library for the Java(tm) platform
003     * ===========================================================
004     *
005     * (C) Copyright 2000-2005, 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 2003-2005, by Object Refinery Limited.
031     *
032     * Original Author:  David Gilbert (for Object Refinery Limited);
033     * Contributor(s):   -;
034     *
035     * $Id $
036     *
037     * Changes
038     * -------
039     * 27-Mar-2003 : Version 1 (DG);
040     * 18-Aug-2003 : Implemented Cloneable (DG);
041     * 03-Mar-2005 : Implemented PublicCloneable (DG);
042     * 
043     */
044    
045    package org.jfree.data.general;
046    
047    import java.io.Serializable;
048    
049    import org.jfree.util.ObjectUtilities;
050    import org.jfree.util.PublicCloneable;
051    
052    /**
053     * A dataset that stores a single value.  This class provides a default 
054     * implementation of the {@link ValueDataset} interface.
055     */
056    public class DefaultValueDataset extends AbstractDataset
057                                     implements ValueDataset, 
058                                                Cloneable, PublicCloneable,
059                                                Serializable {
060    
061        /** For serialization. */
062        private static final long serialVersionUID = 8137521217249294891L;
063        
064        /** The value. */
065        private Number value;
066    
067        /**
068         * Constructs a new dataset, initially empty.
069         */
070        public DefaultValueDataset() {
071            this(null);
072        }
073        
074        /**
075         * Creates a new dataset.
076         * 
077         * @param value  the value.
078         */
079        public DefaultValueDataset(double value) {
080            this(new Double(value));
081        }
082    
083        /**
084         * Creates a new dataset.
085         *
086         * @param value  the initial value.
087         */
088        public DefaultValueDataset(Number value) {
089            this.value = value;
090        }
091    
092        /**
093         * Returns the value.
094         *
095         * @return The value (possibly <code>null</code>).
096         */
097        public Number getValue() {
098            return this.value;
099        }
100    
101        /**
102         * Sets the value and sends a {@link DatasetChangeEvent} to all registered 
103         * listeners.
104         *
105         * @param value  the new value (<code>null</code> permitted).
106         */
107        public void setValue(Number value) {
108            this.value = value;
109            notifyListeners(new DatasetChangeEvent(this, this));
110        }
111    
112        /**
113         * Tests this dataset for equality with an arbitrary object.
114         *
115         * @param obj  the object.
116         *
117         * @return A boolean.
118         */
119        public boolean equals(Object obj) {
120    
121            if (obj == null) {
122                return false;
123            }
124    
125            if (obj == this) {
126                return true;
127            }
128    
129            if (obj instanceof ValueDataset) {
130                ValueDataset vd = (ValueDataset) obj;
131                return ObjectUtilities.equal(this.value, vd.getValue());
132            }
133    
134            return false;
135        }
136    
137        /**
138         * Returns a hash code.
139         * 
140         * @return A hash code.
141         */
142        public int hashCode() {
143            return (this.value != null ? this.value.hashCode() : 0);
144        }
145        
146    }