001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2008, 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 * StandardTickUnitSource.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 * 23-Sep-2003 : Version 1 (DG);
038 * 25-Oct-2007 : Implemented Serializable and equals() method (DG);
039 *
040 */
041
042package org.jfree.chart.axis;
043
044import java.io.Serializable;
045import java.text.DecimalFormat;
046
047/**
048 * A source that can used by the {@link NumberAxis} class to obtain a
049 * suitable {@link TickUnit}.  Instances of this class are {@link Serializable}
050 * from version 1.0.7 onwards.  Cloning is not supported, because instances
051 * are immutable.
052 */
053public class StandardTickUnitSource implements TickUnitSource, Serializable {
054
055    /** Constant for log(10.0). */
056    private static final double LOG_10_VALUE = Math.log(10.0);
057
058    /**
059     * Default constructor.
060     */
061    public StandardTickUnitSource() {
062        super();
063    }
064
065    /**
066     * Returns a tick unit that is larger than the supplied unit.
067     *
068     * @param unit  the unit (<code>null</code> not permitted).
069     *
070     * @return A tick unit that is larger than the supplied unit.
071     */
072    public TickUnit getLargerTickUnit(TickUnit unit) {
073        double x = unit.getSize();
074        double log = Math.log(x) / LOG_10_VALUE;
075        double higher = Math.ceil(log);
076        return new NumberTickUnit(Math.pow(10, higher),
077                new DecimalFormat("0.0E0"));
078    }
079
080    /**
081     * Returns the tick unit in the collection that is greater than or equal
082     * to (in size) the specified unit.
083     *
084     * @param unit  the unit (<code>null</code> not permitted).
085     *
086     * @return A unit from the collection.
087     */
088    public TickUnit getCeilingTickUnit(TickUnit unit) {
089        return getLargerTickUnit(unit);
090    }
091
092    /**
093     * Returns the tick unit in the collection that is greater than or equal
094     * to the specified size.
095     *
096     * @param size  the size.
097     *
098     * @return A unit from the collection.
099     */
100    public TickUnit getCeilingTickUnit(double size) {
101        double log = Math.log(size) / LOG_10_VALUE;
102        double higher = Math.ceil(log);
103        return new NumberTickUnit(Math.pow(10, higher),
104                new DecimalFormat("0.0E0"));
105    }
106
107    /**
108     * Tests this instance for equality with an arbitrary object.
109     *
110     * @param obj  the object (<code>null</code> permitted).
111     *
112     * @return A boolean.
113     */
114    public boolean equals(Object obj) {
115        if (obj == this) {
116            return true;
117        }
118        return (obj instanceof StandardTickUnitSource);
119    }
120
121    /**
122     * Returns a hash code for this instance.
123     *
124     * @return A hash code.
125     */
126    public int hashCode() {
127        return 0;
128    }
129
130}