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 * LogFormat.java
029 * --------------
030 * (C) Copyright 2007, 2008, 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 *
041 */
042
043 package org.jfree.chart.util;
044
045 import java.text.DecimalFormat;
046 import java.text.FieldPosition;
047 import java.text.NumberFormat;
048 import java.text.ParsePosition;
049
050 /**
051 * A number formatter for logarithmic values. This formatter does not support
052 * parsing.
053 *
054 * @since 1.0.7
055 */
056 public class LogFormat extends NumberFormat {
057
058 /** The log base value. */
059 private double base;
060
061 /** The natural logarithm of the base value. */
062 private double baseLog;
063
064 /** The label for the log base (for example, "e"). */
065 private String baseLabel;
066
067 /**
068 * The label for the power symbol.
069 *
070 * @since 1.0.10
071 */
072 private String powerLabel;
073
074 /** A flag that controls whether or not the base is shown. */
075 private boolean showBase;
076
077 /** The number formatter for the exponent. */
078 private NumberFormat formatter = new DecimalFormat("0.0");
079
080 /**
081 * Creates a new instance.
082 *
083 * @param base the base.
084 * @param baseLabel the base label (<code>null</code> not permitted).
085 * @param showBase a flag that controls whether or not the base value is
086 * shown.
087 */
088 public LogFormat(double base, String baseLabel, boolean showBase) {
089 this(base, baseLabel, "^", showBase);
090 }
091
092 /**
093 * Creates a new instance.
094 *
095 * @param base the base.
096 * @param baseLabel the base label (<code>null</code> not permitted).
097 * @param powerLabel the power label (<code>null</code> not permitted).
098 * @param showBase a flag that controls whether or not the base value is
099 * shown.
100 *
101 * @since 1.0.10
102 */
103 public LogFormat(double base, String baseLabel, String powerLabel,
104 boolean showBase) {
105 if (baseLabel == null) {
106 throw new IllegalArgumentException("Null 'baseLabel' argument.");
107 }
108 if (powerLabel == null) {
109 throw new IllegalArgumentException("Null 'powerLabel' argument.");
110 }
111 this.base = base;
112 this.baseLog = Math.log(this.base);
113 this.baseLabel = baseLabel;
114 this.showBase = showBase;
115 this.powerLabel = powerLabel;
116 }
117
118 /**
119 * Calculates the log of a given value.
120 *
121 * @param value the value.
122 *
123 * @return The log of the value.
124 */
125 private double calculateLog(double value) {
126 return Math.log(value) / this.baseLog;
127 }
128
129 /**
130 * Returns a formatted representation of the specified number.
131 *
132 * @param number the number.
133 * @param toAppendTo the string buffer to append to.
134 * @param pos the position.
135 *
136 * @return A string buffer containing the formatted value.
137 */
138 public StringBuffer format(double number, StringBuffer toAppendTo,
139 FieldPosition pos) {
140 StringBuffer result = new StringBuffer();
141 if (this.showBase) {
142 result.append(this.baseLabel);
143 result.append(this.powerLabel);
144 }
145 result.append(this.formatter.format(calculateLog(number)));
146 return result;
147 }
148
149 /**
150 * Formats the specified number as a hexadecimal string. The decimal
151 * fraction is ignored.
152 *
153 * @param number the number to format.
154 * @param toAppendTo the buffer to append to (ignored here).
155 * @param pos the field position (ignored here).
156 *
157 * @return The string buffer.
158 */
159 public StringBuffer format(long number, StringBuffer toAppendTo,
160 FieldPosition pos) {
161 StringBuffer result = new StringBuffer();
162 if (this.showBase) {
163 result.append(this.baseLabel);
164 result.append("^");
165 }
166 result.append(this.formatter.format(calculateLog(number)));
167 return result;
168 }
169
170 /**
171 * Parsing is not implemented, so this method always returns
172 * <code>null</code>.
173 *
174 * @param source ignored.
175 * @param parsePosition ignored.
176 *
177 * @return Always <code>null</code>.
178 */
179 public Number parse (String source, ParsePosition parsePosition) {
180 return null; // don't bother with parsing
181 }
182
183 /**
184 * Tests this formatter for equality with an arbitrary object.
185 *
186 * @param obj the object (<code>null</code> permitted).
187 *
188 * @return A boolean.
189 */
190 public boolean equals(Object obj) {
191 if (obj == this) {
192 return true;
193 }
194 if (!(obj instanceof LogFormat)) {
195 return false;
196 }
197 LogFormat that = (LogFormat) obj;
198 if (this.base != that.base) {
199 return false;
200 }
201 if (!this.baseLabel.equals(that.baseLabel)) {
202 return false;
203 }
204 if (this.baseLog != that.baseLog) {
205 return false;
206 }
207 if (this.showBase != that.showBase) {
208 return false;
209 }
210 return super.equals(obj);
211 }
212
213 /**
214 * Returns a clone of this instance.
215 *
216 * @return A clone.
217 */
218 public Object clone() {
219 LogFormat clone = (LogFormat) super.clone();
220 clone.formatter = (NumberFormat) this.formatter.clone();
221 return clone;
222 }
223
224 }