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