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Java > Open Source Codes > org > riotfamily > common > collection > TypeDifferenceComparator


1 /* ***** BEGIN LICENSE BLOCK *****
2  * Version: MPL 1.1
3  * The contents of this file are subject to the Mozilla Public License Version
4  * 1.1 (the "License"); you may not use this file except in compliance with
5  * the License. You may obtain a copy of the License at
6  * http://www.mozilla.org/MPL/
7  *
8  * Software distributed under the License is distributed on an "AS IS" basis,
9  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
10  * for the specific language governing rights and limitations under the
11  * License.
12  *
13  * The Original Code is Riot.
14  *
15  * The Initial Developer of the Original Code is
16  * Neteye GmbH.
17  * Portions created by the Initial Developer are Copyright (C) 2006
18  * the Initial Developer. All Rights Reserved.
19  *
20  * Contributor(s):
21  * Felix Gnass [fgnass at neteye dot de]
22  *
23  * ***** END LICENSE BLOCK ***** */
24 package org.riotfamily.common.collection;
25
26 import java.util.Comparator JavaDoc;
27
28 /**
29  * Comparator that compares two classes by their hierarchy differnce to a
30  * target class.
31  * <p>
32  * Example:
33  * <pre>
34  * c = new TypeDifferenceComparator(Integer.class);
35  *
36  * c.compare(Object.class, Number.class); // returns 1
37  * c.compare(Integer.class, Number.class); // returns -1
38  * c.compare(Collection.class, Number.class); // returns Integer.MAX_VALUE - 1
39  * c.compare(Collection.class, Object.class); // returns Integer.MAX_VALUE - 2
40  * </pre>
41  * </p>
42  */
43 public class TypeDifferenceComparator implements Comparator JavaDoc {
44
45     private Class JavaDoc targetClass;
46     
47     public TypeDifferenceComparator(Class JavaDoc targetClass) {
48         this.targetClass = targetClass;
49     }
50
51     public int compare(Object JavaDoc o1, Object JavaDoc o2) {
52         return getTypeDifference((Class JavaDoc) o1, targetClass)
53                 - getTypeDifference((Class JavaDoc) o2, targetClass);
54     }
55     
56     /**
57      * <p>
58      * Example:
59      * <pre>
60      * getTypeDifference(Object.class, Integer.class); // returns 2
61      * getTypeDifference(Number.class, Integer.class); // returns 1
62      * getTypeDifference(Integer.class, Integer.class); // returns 0
63      *
64      * getTypeDifference(Integer.class, Float.class); // returns Integer.MAX_VALUE
65      * getTypeDifference(Integer.class, Number.class); // returns Integer.MAX_VALUE
66      * </pre>
67      * </p>
68      */
69     public static int getTypeDifference(Class JavaDoc baseClass, Class JavaDoc subClass) {
70         if (!baseClass.isAssignableFrom(subClass)) {
71             return Integer.MAX_VALUE;
72         }
73         int result = 0;
74         Class JavaDoc superClass = subClass.getSuperclass();
75         while (superClass != null) {
76             if (baseClass.isAssignableFrom(superClass)) {
77                 result++;
78                 superClass = superClass.getSuperclass();
79             }
80             else {
81                 superClass = null;
82             }
83         }
84         return result;
85     }
86
87 }
88
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