001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2022, 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 2007-2022, by David Gilbert and Contributors.
031 *
032 * Original Author:  David Gilbert;
033 * Contributor(s):   -;
034 *
035 */
036
037package org.jfree.chart.text.format;
038
039import java.text.DecimalFormat;
040import java.text.FieldPosition;
041import java.text.NumberFormat;
042import java.text.ParsePosition;
043import org.jfree.chart.internal.Args;
044
045/**
046 * A number formatter for logarithmic values.  This formatter does not support
047 * parsing.
048 */
049public class LogFormat extends NumberFormat {
050
051    /** The log base value. */
052    private double base;
053
054    /** The natural logarithm of the base value. */
055    private double baseLog;
056
057    /** The label for the log base (for example, "e"). */
058    private String baseLabel;
059
060    /**
061     * The label for the power symbol.
062     */
063    private String powerLabel;
064
065    /** A flag that controls whether or not the base is shown. */
066    private boolean showBase;
067
068    /** The number formatter for the exponent. */
069    private NumberFormat formatter = new DecimalFormat("0.0#");
070
071    /**
072     * Creates a new instance using base 10.
073     */
074    public LogFormat() {
075        this(10.0, "10", true);
076    }
077
078    /**
079     * Creates a new instance.
080     *
081     * @param base  the base.
082     * @param baseLabel  the base label ({@code null} not permitted).
083     * @param showBase  a flag that controls whether or not the base value is
084     *                  shown.
085     */
086    public LogFormat(double base, String baseLabel, boolean showBase) {
087        this(base, baseLabel, "^", showBase);
088    }
089
090    /**
091     * Creates a new instance.
092     *
093     * @param base  the base.
094     * @param baseLabel  the base label ({@code null} not permitted).
095     * @param powerLabel  the power label ({@code null} 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, String powerLabel,
100            boolean showBase) {
101        Args.nullNotPermitted(baseLabel, "baseLabel");
102        Args.nullNotPermitted(powerLabel, "powerLabel");
103        this.base = base;
104        this.baseLog = Math.log(this.base);
105        this.baseLabel = baseLabel;
106        this.showBase = showBase;
107        this.powerLabel = powerLabel;
108    }
109
110    /**
111     * Returns the number format used for the exponent.
112     *
113     * @return The number format (never {@code null}).
114     */
115    public NumberFormat getExponentFormat() {
116        return (NumberFormat) this.formatter.clone();
117    }
118
119    /**
120     * Sets the number format used for the exponent.
121     *
122     * @param format  the formatter ({@code null} not permitted).
123     */
124    public void setExponentFormat(NumberFormat format) {
125        Args.nullNotPermitted(format, "format");
126        this.formatter = format;
127    }
128
129    /**
130     * Calculates the log of a given value.
131     *
132     * @param value  the value.
133     *
134     * @return The log of the value.
135     */
136    private double calculateLog(double value) {
137        return Math.log(value) / this.baseLog;
138    }
139
140    /**
141     * Returns a formatted representation of the specified number.
142     *
143     * @param number  the number.
144     * @param toAppendTo  the string buffer to append to.
145     * @param pos  the position.
146     *
147     * @return A string buffer containing the formatted value.
148     */
149    @Override
150    public StringBuffer format(double number, StringBuffer toAppendTo,
151            FieldPosition pos) {
152        StringBuffer result = new StringBuffer();
153        if (this.showBase) {
154            result.append(this.baseLabel);
155            result.append(this.powerLabel);
156        }
157        result.append(this.formatter.format(calculateLog(number)));
158        return result;
159    }
160
161    /**
162     * Formats the specified number as a hexadecimal string.  The decimal
163     * fraction is ignored.
164     *
165     * @param number  the number to format.
166     * @param toAppendTo  the buffer to append to (ignored here).
167     * @param pos  the field position (ignored here).
168     *
169     * @return The string buffer.
170     */
171    @Override
172    public StringBuffer format(long number, StringBuffer toAppendTo,
173            FieldPosition pos) {
174        StringBuffer result = new StringBuffer();
175        if (this.showBase) {
176            result.append(this.baseLabel);
177            result.append(this.powerLabel);
178        }
179        result.append(this.formatter.format(calculateLog(number)));
180        return result;
181    }
182
183    /**
184     * Parsing is not implemented, so this method always returns
185     * {@code null}.
186     *
187     * @param source  ignored.
188     * @param parsePosition  ignored.
189     *
190     * @return Always {@code null}.
191     */
192    @Override
193    public Number parse (String source, ParsePosition parsePosition) {
194        return null; // don't bother with parsing
195    }
196
197    /**
198     * Tests this formatter for equality with an arbitrary object.
199     *
200     * @param obj  the object ({@code null} permitted).
201     *
202     * @return A boolean.
203     */
204    @Override
205    public boolean equals(Object obj) {
206        if (obj == this) {
207            return true;
208        }
209        if (!(obj instanceof LogFormat)) {
210            return false;
211        }
212        LogFormat that = (LogFormat) obj;
213        if (this.base != that.base) {
214            return false;
215        }
216        if (!this.baseLabel.equals(that.baseLabel)) {
217            return false;
218        }
219        if (this.baseLog != that.baseLog) {
220            return false;
221        }
222        if (this.showBase != that.showBase) {
223            return false;
224        }
225        if (!this.formatter.equals(that.formatter)) {
226            return false;
227        }
228        return super.equals(obj);
229    }
230
231    /**
232     * Returns a clone of this instance.
233     *
234     * @return A clone.
235     */
236    @Override
237    public Object clone() {
238        LogFormat clone = (LogFormat) super.clone();
239        clone.formatter = (NumberFormat) this.formatter.clone();
240        return clone;
241    }
242
243}