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     * $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     * ------------- JFREECHART 1.0.x ---------------------------------------------
043     * 30-Jan-2007 : Added explicit super() call in constructor (for clarity) (DG);
044     * 
045     */
046    
047    package org.jfree.data.general;
048    
049    import java.io.Serializable;
050    
051    import org.jfree.util.ObjectUtilities;
052    import org.jfree.util.PublicCloneable;
053    
054    /**
055     * A dataset that stores a single value (that is possibly <code>null</code>).  
056     * This class provides a default implementation of the {@link ValueDataset} 
057     * interface.
058     */
059    public class DefaultValueDataset extends AbstractDataset
060                                     implements ValueDataset, 
061                                                Cloneable, PublicCloneable,
062                                                Serializable {
063    
064        /** For serialization. */
065        private static final long serialVersionUID = 8137521217249294891L;
066        
067        /** The value. */
068        private Number value;
069    
070        /**
071         * Constructs a new dataset, initially empty.
072         */
073        public DefaultValueDataset() {
074            this(null);
075        }
076        
077        /**
078         * Creates a new dataset with the specified value.
079         * 
080         * @param value  the value.
081         */
082        public DefaultValueDataset(double value) {
083            this(new Double(value));
084        }
085    
086        /**
087         * Creates a new dataset with the specified value.
088         *
089         * @param value  the initial value (<code>null</code> permitted).
090         */
091        public DefaultValueDataset(Number value) {
092            super();
093            this.value = value;
094        }
095    
096        /**
097         * Returns the value.
098         *
099         * @return The value (possibly <code>null</code>).
100         */
101        public Number getValue() {
102            return this.value;
103        }
104    
105        /**
106         * Sets the value and sends a {@link DatasetChangeEvent} to all registered 
107         * listeners.
108         *
109         * @param value  the new value (<code>null</code> permitted).
110         */
111        public void setValue(Number value) {
112            this.value = value;
113            notifyListeners(new DatasetChangeEvent(this, this));
114        }
115    
116        /**
117         * Tests this dataset for equality with an arbitrary object.
118         *
119         * @param obj  the object (<code>null</code> permitted).
120         *
121         * @return A boolean.
122         */
123        public boolean equals(Object obj) {
124            if (obj == this) {
125                return true;
126            }
127            if (obj instanceof ValueDataset) {
128                ValueDataset vd = (ValueDataset) obj;
129                return ObjectUtilities.equal(this.value, vd.getValue());
130            }
131            return false;
132        }
133    
134        /**
135         * Returns a hash code.
136         * 
137         * @return A hash code.
138         */
139        public int hashCode() {
140            return (this.value != null ? this.value.hashCode() : 0);
141        }
142        
143    }