    001/* ===========================================================
    002 * JFreeChart : a free chart library for the Java(tm) platform
    003 * ===========================================================
    004 *
    005 * (C) Copyright 2000-2011, 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 * LogFormat.java
    029 * --------------
    030 * (C) Copyright 2007-2009, by Object Refinery Limited and Contributors.
    031 *
    032 * Original Author:  David Gilbert (for Object Refinery Limited);
    033 * Contributor(s):   -;
    034 *
    035 * Changes
    036 * -------
    037 * 02-Aug-2007 : Version 1 (DG);
    038 * 19-Feb-2008 : Implemented equals() and clone(), and added new powerLabel
    039 *               attribute as per Feature Request 1886036 (DG);
    040 * 14-Jan-2009 : Added default constructor, and accessor methods for
    041 *               exponent formatter (DG);
    042 *
    043 */
    044
    045package org.jfree.chart.util;
    046
    047import java.text.DecimalFormat;
    048import java.text.FieldPosition;
    049import java.text.NumberFormat;
    050import java.text.ParsePosition;
    051
    052/**
    053 * A number formatter for logarithmic values.  This formatter does not support
    054 * parsing.
    055 *
    056 * @since 1.0.7
    057 */
    058public class LogFormat extends NumberFormat {
    059
    060    /** The log base value. */
    061    private double base;
    062
    063    /** The natural logarithm of the base value. */
    064    private double baseLog;
    065
    066    /** The label for the log base (for example, "e"). */
    067    private String baseLabel;
    068
    069    /**
    070     * The label for the power symbol.
    071     *
    072     * @since 1.0.10
    073     */
    074    private String powerLabel;
    075
    076    /** A flag that controls whether or not the base is shown. */
    077    private boolean showBase;
    078
    079    /** The number formatter for the exponent. */
    080    private NumberFormat formatter = new DecimalFormat("0.0#");
    081
    082    /**
    083     * Creates a new instance using base 10.
    084     *
    085     * @since 1.0.13
    086     */
    087    public LogFormat() {
    088        this(10.0, "10", true);
    089    }
    090
    091    /**
    092     * Creates a new instance.
    093     *
    094     * @param base  the base.
    095     * @param baseLabel  the base label (<code>null</code> not permitted).
    096     * @param showBase  a flag that controls whether or not the base value is
    097     *                  shown.
    098     */
    099    public LogFormat(double base, String baseLabel, boolean showBase) {
    100        this(base, baseLabel, "^", showBase);
    101    }
    102
    103    /**
    104     * Creates a new instance.
    105     *
    106     * @param base  the base.
    107     * @param baseLabel  the base label (<code>null</code> not permitted).
    108     * @param powerLabel  the power label (<code>null</code> not permitted).
    109     * @param showBase  a flag that controls whether or not the base value is
    110     *                  shown.
    111     *
    112     * @since 1.0.10
    113     */
    114    public LogFormat(double base, String baseLabel, String powerLabel,
    115            boolean showBase) {
    116        if (baseLabel == null) {
    117            throw new IllegalArgumentException("Null 'baseLabel' argument.");
    118        }
    119        if (powerLabel == null) {
    120            throw new IllegalArgumentException("Null 'powerLabel' argument.");
    121        }
    122        this.base = base;
    123        this.baseLog = Math.log(this.base);
    124        this.baseLabel = baseLabel;
    125        this.showBase = showBase;
    126        this.powerLabel = powerLabel;
    127    }
    128
    129    /**
    130     * Returns the number format used for the exponent.
    131     *
    132     * @return The number format (never <code>null</code>).
    133     *
    134     * @since 1.0.13.
    135     */
    136    public NumberFormat getExponentFormat() {
    137        return (NumberFormat) this.formatter.clone();
    138    }
    139
    140    /**
    141     * Sets the number format used for the exponent.
    142     *
    143     * @param format  the formatter (<code>null</code> not permitted).
    144     *
    145     * @since 1.0.13
    146     */
    147    public void setExponentFormat(NumberFormat format) {
    148        if (format == null) {
    149            throw new IllegalArgumentException("Null 'format' argument.");
    150        }
    151        this.formatter = format;
    152    }
    153
    154    /**
    155     * Calculates the log of a given value.
    156     *
    157     * @param value  the value.
    158     *
    159     * @return The log of the value.
    160     */
    161    private double calculateLog(double value) {
    162        return Math.log(value) / this.baseLog;
    163    }
    164
    165    /**
    166     * Returns a formatted representation of the specified number.
    167     *
    168     * @param number  the number.
    169     * @param toAppendTo  the string buffer to append to.
    170     * @param pos  the position.
    171     *
    172     * @return A string buffer containing the formatted value.
    173     */
    174    public StringBuffer format(double number, StringBuffer toAppendTo,
    175            FieldPosition pos) {
    176        StringBuffer result = new StringBuffer();
    177        if (this.showBase) {
    178            result.append(this.baseLabel);
    179            result.append(this.powerLabel);
    180        }
    181        result.append(this.formatter.format(calculateLog(number)));
    182        return result;
    183    }
    184
    185    /**
    186     * Formats the specified number as a hexadecimal string.  The decimal
    187     * fraction is ignored.
    188     *
    189     * @param number  the number to format.
    190     * @param toAppendTo  the buffer to append to (ignored here).
    191     * @param pos  the field position (ignored here).
    192     *
    193     * @return The string buffer.
    194     */
    195    public StringBuffer format(long number, StringBuffer toAppendTo,
    196            FieldPosition pos) {
    197        StringBuffer result = new StringBuffer();
    198        if (this.showBase) {
    199            result.append(this.baseLabel);
    200            result.append(this.powerLabel);
    201        }
    202        result.append(this.formatter.format(calculateLog(number)));
    203        return result;
    204    }
    205
    206    /**
    207     * Parsing is not implemented, so this method always returns
    208     * <code>null</code>.
    209     *
    210     * @param source  ignored.
    211     * @param parsePosition  ignored.
    212     *
    213     * @return Always <code>null</code>.
    214     */
    215    public Number parse (String source, ParsePosition parsePosition) {
    216        return null; // don't bother with parsing
    217    }
    218
    219    /**
    220     * Tests this formatter for equality with an arbitrary object.
    221     *
    222     * @param obj  the object (<code>null</code> permitted).
    223     *
    224     * @return A boolean.
    225     */
    226    public boolean equals(Object obj) {
    227        if (obj == this) {
    228            return true;
    229        }
    230        if (!(obj instanceof LogFormat)) {
    231            return false;
    232        }
    233        LogFormat that = (LogFormat) obj;
    234        if (this.base != that.base) {
    235            return false;
    236        }
    237        if (!this.baseLabel.equals(that.baseLabel)) {
    238            return false;
    239        }
    240        if (this.baseLog != that.baseLog) {
    241            return false;
    242        }
    243        if (this.showBase != that.showBase) {
    244            return false;
    245        }
    246        if (!this.formatter.equals(that.formatter)) {
    247            return false;
    248        }
    249        return super.equals(obj);
    250    }
    251
    252    /**
    253     * Returns a clone of this instance.
    254     *
    255     * @return A clone.
    256     */
    257    public Object clone() {
    258        LogFormat clone = (LogFormat) super.clone();
    259        clone.formatter = (NumberFormat) this.formatter.clone();
    260        return clone;
    261    }
    262
    263}