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jfreechart example source code file (LogFormat.java)

This example jfreechart source code file (LogFormat.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - jfreechart tags/keywords

decimalformat, fieldposition, illegalargumentexception, logformat, logformat, null, number, numberformat, numberformat, parseposition, string, string, stringbuffer, stringbuffer, text

The jfreechart LogFormat.java source code

/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-2009, 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.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
 * in the United States and other countries.]
 *
 * --------------
 * LogFormat.java
 * --------------
 * (C) Copyright 2007-2009, 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);
 *
 */

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 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 not permitted).
     * @param powerLabel  the power label (<code>null 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) {
        if (baseLabel == null) {
            throw new IllegalArgumentException("Null 'baseLabel' argument.");
        }
        if (powerLabel == null) {
            throw new IllegalArgumentException("Null 'powerLabel' argument.");
        }
        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).
     *
     * @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 not permitted).
     *
     * @since 1.0.13
     */
    public void setExponentFormat(NumberFormat format) {
        if (format == null) {
            throw new IllegalArgumentException("Null 'format' argument.");
        }
        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.
     */
    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.
     */
    public StringBuffer format(long number, StringBuffer toAppendTo,
            FieldPosition pos) {
        StringBuffer result = new StringBuffer();
        if (this.showBase) {
            result.append(this.baseLabel);
            result.append("^");
        }
        result.append(this.formatter.format(calculateLog(number)));
        return result;
    }

    /**
     * Parsing is not implemented, so this method always returns
     * <code>null.
     *
     * @param source  ignored.
     * @param parsePosition  ignored.
     *
     * @return Always <code>null.
     */
    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 permitted).
     *
     * @return A boolean.
     */
    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.
     */
    public Object clone() {
        LogFormat clone = (LogFormat) super.clone();
        clone.formatter = (NumberFormat) this.formatter.clone();
        return clone;
    }

}

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