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Java > Open Source Codes > org > apache > geronimo > kernel > classloader > UnionEnumeration


1 /**
2  * Licensed to the Apache Software Foundation (ASF) under one or more
3  * contributor license agreements. See the NOTICE file distributed with
4  * this work for additional information regarding copyright ownership.
5  * The ASF licenses this file to You under the Apache License, Version 2.0
6  * (the "License"); you may not use this file except in compliance with
7  * the License. You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */

17 package org.apache.geronimo.kernel.classloader;
18
19 import java.util.Enumeration JavaDoc;
20 import java.util.LinkedList JavaDoc;
21 import java.util.List JavaDoc;
22 import java.util.NoSuchElementException JavaDoc;
23
24 /**
25  * @version $Rev: 476049 $ $Date: 2006-11-16 23:35:17 -0500 (Thu, 16 Nov 2006) $
26  */

27 public final class UnionEnumeration implements Enumeration JavaDoc {
28     private final LinkedList JavaDoc enumerations = new LinkedList JavaDoc();
29
30     public UnionEnumeration(List JavaDoc enumerations) {
31         this.enumerations.addAll(enumerations);
32     }
33
34     public UnionEnumeration(Enumeration JavaDoc first, Enumeration JavaDoc second) {
35         if (first == null) throw new NullPointerException JavaDoc("first is null");
36         if (second == null) throw new NullPointerException JavaDoc("second is null");
37
38         enumerations.add(first);
39         enumerations.add(second);
40     }
41
42     public boolean hasMoreElements() {
43         while (!enumerations.isEmpty()) {
44             Enumeration JavaDoc enumeration = (Enumeration JavaDoc) enumerations.getFirst();
45             if (enumeration.hasMoreElements()) {
46                 return true;
47             }
48             enumerations.removeFirst();
49         }
50         return false;
51     }
52
53     public Object JavaDoc nextElement() {
54         while (!enumerations.isEmpty()) {
55             Enumeration JavaDoc enumeration = (Enumeration JavaDoc) enumerations.getFirst();
56             if (enumeration.hasMoreElements()) {
57                 return enumeration.nextElement();
58             }
59             enumerations.removeFirst();
60         }
61         throw new NoSuchElementException JavaDoc();
62     }
63 }
64
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