001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2009, 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 * 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("^");
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}