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