1 /**
2 *
3 * Copyright 2005 The Apache Software Foundation
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * 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;
20 import java.util.LinkedList;
21 import java.util.List;
22 import java.util.NoSuchElementException;
23
24 /**
25 * @version $Rev: 410741 $ $Date: 2006-05-31 21:35:48 -0700 (Wed, 31 May 2006) $
26 */
27 public final class UnionEnumeration implements Enumeration {
28 private final LinkedList enumerations = new LinkedList();
29
30 public UnionEnumeration(List enumerations) {
31 this.enumerations.addAll(enumerations);
32 }
33
34 public UnionEnumeration(Enumeration first, Enumeration second) {
35 if (first == null) throw new NullPointerException("first is null");
36 if (second == null) throw new NullPointerException("second is null");
37
38 enumerations.add(first);
39 enumerations.add(second);
40 }
41
42 public boolean hasMoreElements() {
43 while (!enumerations.isEmpty()) {
44 Enumeration enumeration = (Enumeration) enumerations.getFirst();
45 if (enumeration.hasMoreElements()) {
46 return true;
47 }
48 enumerations.removeFirst();
49 }
50 return false;
51 }
52
53 public Object nextElement() {
54 while (!enumerations.isEmpty()) {
55 Enumeration enumeration = (Enumeration) enumerations.getFirst();
56 if (enumeration.hasMoreElements()) {
57 return enumeration.nextElement();
58 }
59 enumerations.removeFirst();
60 }
61 throw new NoSuchElementException();
62 }
63 }