Source for org.jfree.chart.util.LogFormat

   1: /* ===========================================================
   2:  * JFreeChart : a free chart library for the Java(tm) platform
   3:  * ===========================================================
   4:  *
   5:  * (C) Copyright 2000-2008, by Object Refinery Limited and Contributors.
   6:  *
   7:  * Project Info:  http://www.jfree.org/jfreechart/index.html
   8:  *
   9:  * This library is free software; you can redistribute it and/or modify it
  10:  * under the terms of the GNU Lesser General Public License as published by
  11:  * the Free Software Foundation; either version 2.1 of the License, or
  12:  * (at your option) any later version.
  13:  *
  14:  * This library is distributed in the hope that it will be useful, but
  15:  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  16:  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
  17:  * License for more details.
  18:  *
  19:  * You should have received a copy of the GNU Lesser General Public
  20:  * License along with this library; if not, write to the Free Software
  21:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
  22:  * USA.  
  23:  *
  24:  * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
  25:  * in the United States and other countries.]
  26:  *
  27:  * --------------
  28:  * LogFormat.java
  29:  * --------------
  30:  * (C) Copyright 2007, 2008, by Object Refinery Limited and Contributors.
  31:  *
  32:  * Original Author:  David Gilbert (for Object Refinery Limited);
  33:  * Contributor(s):   -;
  34:  *
  35:  * Changes
  36:  * -------
  37:  * 02-Aug-2007 : Version 1 (DG);
  38:  * 19-Feb-2008 : Implemented equals() and clone(), and added new powerLabel
  39:  *               attribute as per Feature Request 1886036 (DG);
  40:  * 
  41:  */
  42: 
  43: package org.jfree.chart.util;
  44: 
  45: import java.text.DecimalFormat;
  46: import java.text.FieldPosition;
  47: import java.text.NumberFormat;
  48: import java.text.ParsePosition;
  49: 
  50: /**
  51:  * A number formatter for logarithmic values.  This formatter does not support
  52:  * parsing.
  53:  * 
  54:  * @since 1.0.7
  55:  */
  56: public class LogFormat extends NumberFormat {
  57:     
  58:     /** The log base value. */
  59:     private double base;
  60:     
  61:     /** The natural logarithm of the base value. */
  62:     private double baseLog;
  63:     
  64:     /** The label for the log base (for example, "e"). */
  65:     private String baseLabel;
  66:     
  67:     /** 
  68:      * The label for the power symbol.
  69:      * 
  70:      * @since 1.0.10
  71:      */
  72:     private String powerLabel;
  73:     
  74:     /** A flag that controls whether or not the base is shown. */
  75:     private boolean showBase;
  76:     
  77:     /** The number formatter for the exponent. */
  78:     private NumberFormat formatter = new DecimalFormat("0.0");
  79:     
  80:     /**
  81:      * Creates a new instance.
  82:      * 
  83:      * @param base  the base.
  84:      * @param baseLabel  the base label (<code>null</code> not permitted).
  85:      * @param showBase  a flag that controls whether or not the base value is
  86:      *                  shown.
  87:      */
  88:     public LogFormat(double base, String baseLabel, boolean showBase) {
  89:         this(base, baseLabel, "^", showBase);
  90:     }
  91:     
  92:     /**
  93:      * Creates a new instance.
  94:      * 
  95:      * @param base  the base.
  96:      * @param baseLabel  the base label (<code>null</code> not permitted).
  97:      * @param powerLabel  the power label (<code>null</code> not permitted).
  98:      * @param showBase  a flag that controls whether or not the base value is
  99:      *                  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: }