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Java > Open Source Codes > org > jfree > chart > axis > StandardTickUnitSource


1 /* ===========================================================
2  * JFreeChart : a free chart library for the Java(tm) platform
3  * ===========================================================
4  *
5  * (C) Copyright 2000-2005, 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 License
20  * along with this library; if not, write to the Free Software Foundation,
21  * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
22  *
23  * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
24  * in the United States and other countries.]
25  *
26  * ---------------------------
27  * StandardTickUnitSource.java
28  * ---------------------------
29  * (C) Copyright 2003, 2004, by Object Refinery Limited.
30  *
31  * Original Author: David Gilbert (for Object Refinery Limited);
32  * Contributor(s): -;
33  *
34  * $Id: StandardTickUnitSource.java,v 1.2 2005/03/16 12:09:18 mungady Exp $
35  *
36  * Changes
37  * -------
38  * 23-Sep-2003 : Version 1 (DG);
39  *
40  */
41
42 package org.jfree.chart.axis;
43
44 import java.text.DecimalFormat JavaDoc;
45
46 /**
47  * A source that can used by the {@link NumberAxis} class to obtain a
48  * suitable {@link TickUnit}.
49  *
50  */
51 public class StandardTickUnitSource implements TickUnitSource {
52
53     /** Constant for log(10.0). */
54     private static final double LOG_10_VALUE = Math.log(10.0);
55     
56     /**
57      * Returns a tick unit that is larger than the supplied unit.
58      *
59      * @param unit the unit.
60      *
61      * @return A tick unit that is larger than the supplied unit.
62      */
63     public TickUnit getLargerTickUnit(TickUnit unit) {
64         double x = unit.getSize();
65         double log = Math.log(x) / LOG_10_VALUE;
66         double higher = Math.ceil(log);
67         return new NumberTickUnit(
68             Math.pow(10, higher), new DecimalFormat JavaDoc("0.0E0")
69         );
70     }
71
72     /**
73      * Returns the tick unit in the collection that is greater than or equal
74      * to (in size) the specified unit.
75      *
76      * @param unit the unit.
77      *
78      * @return A unit from the collection.
79      */
80     public TickUnit getCeilingTickUnit(TickUnit unit) {
81         return getLargerTickUnit(unit);
82     }
83
84     /**
85      * Returns the tick unit in the collection that is greater than or equal
86      * to the specified size.
87      *
88      * @param size the size.
89      *
90      * @return A unit from the collection.
91      */
92     public TickUnit getCeilingTickUnit(double size) {
93         double log = Math.log(size) / LOG_10_VALUE;
94         double higher = Math.ceil(log);
95         return new NumberTickUnit(
96             Math.pow(10, higher), new DecimalFormat JavaDoc("0.0E0")
97         );
98     }
99     
100 }
101
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