standardtickunitsource.java

jfreechart安装程序和使用说明

/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-2004, 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., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * ---------------------------
 * StandardTickUnitSource.java
 * ---------------------------
 * (C) Copyright 2003, 2004, by Object Refinery Limited.
 *
 * Original Author:  David Gilbert (for Object Refinery Limited);
 * Contributor(s):   -;
 *
 * $Id: StandardTickUnitSource.java,v 1.1 2004/08/31 14:30:24 mungady Exp $
 *
 * Changes
 * -------
 * 23-Sep-2003 : Version 1 (DG);
 *
 */

package org.jfree.chart.axis;

import java.text.DecimalFormat;

/**
 * A source that can used by the {@link NumberAxis} class to obtain a
 * suitable {@link TickUnit}.
 *
 */
public class StandardTickUnitSource implements TickUnitSource {

    /** Constant for log(10.0). */
    private static final double LOG_10_VALUE = Math.log(10.0);
    
    /**
     * Returns a tick unit that is larger than the supplied unit.
     *
     * @param unit   the unit.
     *
     * @return A tick unit that is larger than the supplied unit.
     */
    public TickUnit getLargerTickUnit(TickUnit unit) {
        double x = unit.getSize();
        double log = Math.log(x) / LOG_10_VALUE;
        double higher = Math.ceil(log);
        return new NumberTickUnit(Math.pow(10, higher), new DecimalFormat("0.0E0"));
    }

    /**
     * Returns the tick unit in the collection that is greater than or equal
     * to (in size) the specified unit.
     *
     * @param unit  the unit.
     *
     * @return A unit from the collection.
     */
    public TickUnit getCeilingTickUnit(TickUnit unit) {
        return getLargerTickUnit(unit);
    }

    /**
     * Returns the tick unit in the collection that is greater than or equal
     * to the specified size.
     *
     * @param size  the size.
     *
     * @return A unit from the collection.
     */
    public TickUnit getCeilingTickUnit(double size) {
        double log = Math.log(size) / LOG_10_VALUE;
        double higher = Math.ceil(log);
        return new NumberTickUnit(Math.pow(10, higher), new DecimalFormat("0.0E0"));
    }
    
}