001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2020, 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 * [Oracle and Java are registered trademarks of Oracle and/or its affiliates. 
025 * Other names may be trademarks of their respective owners.]
026 *
027 * ------------------------
028 * DefaultValueDataset.java
029 * ------------------------
030 * (C) Copyright 2003-2008, 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;
048import org.jfree.chart.util.ObjectUtils;
049import org.jfree.chart.util.PublicCloneable;
050
051/**
052 * A dataset that stores a single value (that is possibly {@code null}).
053 * This class provides a default implementation of the {@link ValueDataset}
054 * interface.
055 */
056public class DefaultValueDataset extends AbstractDataset
057        implements ValueDataset, Cloneable, PublicCloneable, Serializable {
058
059    /** For serialization. */
060    private static final long serialVersionUID = 8137521217249294891L;
061
062    /** The value. */
063    private Number value;
064
065    /**
066     * Constructs a new dataset, initially empty.
067     */
068    public DefaultValueDataset() {
069        this(null);
070    }
071
072    /**
073     * Creates a new dataset with the specified value.
074     *
075     * @param value  the value.
076     */
077    public DefaultValueDataset(double value) {
078        this(Double.valueOf(value));
079    }
080
081    /**
082     * Creates a new dataset with the specified value.
083     *
084     * @param value  the initial value ({@code null} permitted).
085     */
086    public DefaultValueDataset(Number value) {
087        super();
088        this.value = value;
089    }
090
091    /**
092     * Returns the value.
093     *
094     * @return The value (possibly {@code null}).
095     */
096    @Override
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} 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 ({@code null} permitted).
116     *
117     * @return A boolean.
118     */
119    @Override
120    public boolean equals(Object obj) {
121        if (obj == this) {
122            return true;
123        }
124        if (obj instanceof ValueDataset) {
125            ValueDataset vd = (ValueDataset) obj;
126            return ObjectUtils.equal(this.value, vd.getValue());
127        }
128        return false;
129    }
130
131    /**
132     * Returns a hash code.
133     *
134     * @return A hash code.
135     */
136    @Override
137    public int hashCode() {
138        return (this.value != null ? this.value.hashCode() : 0);
139    }
140
141}