Java tutorial
/* =========================================================== * JFreeChart : a free chart library for the Java(tm) platform * =========================================================== * * (C) Copyright 2000-2013, by Object Refinery Limited and Contributors. * * Project Info: http://www.jfree.org/jfreechart/index.html * * This library is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation; either version 2.1 of the License, or * (at your option) any later version. * * This library is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public * License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, * USA. * * [Oracle and Java are registered trademarks of Oracle and/or its affiliates. * Other names may be trademarks of their respective owners.] * * -------------- * LogFormat.java * -------------- * (C) Copyright 2007-2013, by Object Refinery Limited and Contributors. * * Original Author: David Gilbert (for Object Refinery Limited); * Contributor(s): -; * * Changes * ------- * 02-Aug-2007 : Version 1 (DG); * 19-Feb-2008 : Implemented equals() and clone(), and added new powerLabel * attribute as per Feature Request 1886036 (DG); * 14-Jan-2009 : Added default constructor, and accessor methods for * exponent formatter (DG); * 03-Jul-2013 : Use ParamChecks (DG); * */ package org.jfree.chart.util; import java.text.DecimalFormat; import java.text.FieldPosition; import java.text.NumberFormat; import java.text.ParsePosition; /** * A number formatter for logarithmic values. This formatter does not support * parsing. * * @since 1.0.7 */ public class LogFormat extends NumberFormat { /** The log base value. */ private double base; /** The natural logarithm of the base value. */ private double baseLog; /** The label for the log base (for example, "e"). */ private String baseLabel; /** * The label for the power symbol. * * @since 1.0.10 */ private String powerLabel; /** A flag that controls whether or not the base is shown. */ private boolean showBase; /** The number formatter for the exponent. */ private NumberFormat formatter = new DecimalFormat("0.0#"); /** * Creates a new instance using base 10. * * @since 1.0.13 */ public LogFormat() { this(10.0, "10", true); } /** * Creates a new instance. * * @param base the base. * @param baseLabel the base label (<code>null</code> not permitted). * @param showBase a flag that controls whether or not the base value is * shown. */ public LogFormat(double base, String baseLabel, boolean showBase) { this(base, baseLabel, "^", showBase); } /** * Creates a new instance. * * @param base the base. * @param baseLabel the base label (<code>null</code> not permitted). * @param powerLabel the power label (<code>null</code> not permitted). * @param showBase a flag that controls whether or not the base value is * shown. * * @since 1.0.10 */ public LogFormat(double base, String baseLabel, String powerLabel, boolean showBase) { ParamChecks.nullNotPermitted(baseLabel, "baseLabel"); ParamChecks.nullNotPermitted(powerLabel, "powerLabel"); this.base = base; this.baseLog = Math.log(this.base); this.baseLabel = baseLabel; this.showBase = showBase; this.powerLabel = powerLabel; } /** * Returns the number format used for the exponent. * * @return The number format (never <code>null</code>). * * @since 1.0.13. */ public NumberFormat getExponentFormat() { return (NumberFormat) this.formatter.clone(); } /** * Sets the number format used for the exponent. * * @param format the formatter (<code>null</code> not permitted). * * @since 1.0.13 */ public void setExponentFormat(NumberFormat format) { ParamChecks.nullNotPermitted(format, "format"); this.formatter = format; } /** * Calculates the log of a given value. * * @param value the value. * * @return The log of the value. */ private double calculateLog(double value) { return Math.log(value) / this.baseLog; } /** * Returns a formatted representation of the specified number. * * @param number the number. * @param toAppendTo the string buffer to append to. * @param pos the position. * * @return A string buffer containing the formatted value. */ @Override public StringBuffer format(double number, StringBuffer toAppendTo, FieldPosition pos) { StringBuffer result = new StringBuffer(); if (this.showBase) { result.append(this.baseLabel); result.append(this.powerLabel); } result.append(this.formatter.format(calculateLog(number))); return result; } /** * Formats the specified number as a hexadecimal string. The decimal * fraction is ignored. * * @param number the number to format. * @param toAppendTo the buffer to append to (ignored here). * @param pos the field position (ignored here). * * @return The string buffer. */ @Override public StringBuffer format(long number, StringBuffer toAppendTo, FieldPosition pos) { StringBuffer result = new StringBuffer(); if (this.showBase) { result.append(this.baseLabel); result.append(this.powerLabel); } result.append(this.formatter.format(calculateLog(number))); return result; } /** * Parsing is not implemented, so this method always returns * <code>null</code>. * * @param source ignored. * @param parsePosition ignored. * * @return Always <code>null</code>. */ @Override public Number parse(String source, ParsePosition parsePosition) { return null; // don't bother with parsing } /** * Tests this formatter for equality with an arbitrary object. * * @param obj the object (<code>null</code> permitted). * * @return A boolean. */ @Override public boolean equals(Object obj) { if (obj == this) { return true; } if (!(obj instanceof LogFormat)) { return false; } LogFormat that = (LogFormat) obj; if (this.base != that.base) { return false; } if (!this.baseLabel.equals(that.baseLabel)) { return false; } if (this.baseLog != that.baseLog) { return false; } if (this.showBase != that.showBase) { return false; } if (!this.formatter.equals(that.formatter)) { return false; } return super.equals(obj); } /** * Returns a clone of this instance. * * @return A clone. */ @Override public Object clone() { LogFormat clone = (LogFormat) super.clone(); clone.formatter = (NumberFormat) this.formatter.clone(); return clone; } }