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Java > Open Source Codes > net > sf > cglib > core > CollectionUtils


1 /*
2  * Copyright 2003,2004 The Apache Software Foundation
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 net.sf.cglib.core;
17
18 import java.util.*;
19 import java.lang.reflect.Array JavaDoc;
20
21 /**
22  * @author Chris Nokleberg
23  * @version $Id: CollectionUtils.java,v 1.7 2004/06/24 21:15:21 herbyderby Exp $
24  */
25 public class CollectionUtils {
26     private CollectionUtils() { }
27
28     public static Map bucket(Collection c, Transformer t) {
29         Map buckets = new HashMap();
30         for (Iterator it = c.iterator(); it.hasNext();) {
31             Object JavaDoc value = (Object JavaDoc)it.next();
32             Object JavaDoc key = t.transform(value);
33             List bucket = (List)buckets.get(key);
34             if (bucket == null) {
35                 buckets.put(key, bucket = new LinkedList());
36             }
37             bucket.add(value);
38         }
39         return buckets;
40     }
41
42     public static void reverse(Map source, Map target) {
43         for (Iterator it = source.keySet().iterator(); it.hasNext();) {
44             Object JavaDoc key = it.next();
45             target.put(source.get(key), key);
46         }
47     }
48
49     public static Collection filter(Collection c, Predicate p) {
50         Iterator it = c.iterator();
51         while (it.hasNext()) {
52             if (!p.evaluate(it.next())) {
53                 it.remove();
54             }
55         }
56         return c;
57     }
58
59     public static List transform(Collection c, Transformer t) {
60         List result = new ArrayList(c.size());
61         for (Iterator it = c.iterator(); it.hasNext();) {
62             result.add(t.transform(it.next()));
63         }
64         return result;
65     }
66
67     public static Map getIndexMap(List list) {
68         Map indexes = new HashMap();
69         int index = 0;
70         for (Iterator it = list.iterator(); it.hasNext();) {
71             indexes.put(it.next(), new Integer JavaDoc(index++));
72         }
73         return indexes;
74     }
75 }
76     
77
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