1 /*
2 * Copyright 2005-2008 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package org.springframework.ldap.support;
17
18 import java.io.Serializable;
19 import java.util.Comparator;
20 import java.util.List;
21
22 /**
23 * Comparator for comparing lists of Comparable objects.
24 *
25 * @author Mattias Hellborg Arthursson
26 */
27 public class ListComparator implements Comparator, Serializable {
28 private static final long serialVersionUID = -3068381879731157178L;
29
30 /**
31 * Compare two lists of Comparable objects.
32 *
33 * @param o1 the first object to be compared.
34 * @param o2 the second object to be compared.
35 * @throws ClassCastException if any of the lists contains an object that
36 * is not Comparable.
37 */
38 public int compare(Object o1, Object o2) {
39 List list1 = (List) o1;
40 List list2 = (List) o2;
41
42 for (int i = 0; i < list1.size(); i++) {
43 if (list2.size() > i) {
44 Comparable component1 = (Comparable) list1.get(i);
45 Comparable component2 = (Comparable) list2.get(i);
46 int componentsCompared = component1.compareTo(component2);
47 if (componentsCompared != 0) {
48 return componentsCompared;
49 }
50 }
51 else {
52 // First instance has more components, so that instance is
53 // greater.
54 return 1;
55 }
56 }
57
58 // All components so far are equal - if the other instance has
59 // more components it is greater otherwise they are equal.
60 if (list2.size() > list1.size()) {
61 return -1;
62 }
63 else {
64 return 0;
65 }
66 }
67 }