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.commons.collections4;
18
19 import java.util.ArrayList;
20 import java.util.Enumeration;
21 import java.util.List;
22 import java.util.StringTokenizer;
23
24 import org.apache.commons.collections4.iterators.EnumerationIterator;
25 import org.apache.commons.collections4.iterators.IteratorIterable;
26
27 /**
28 * Provides utility methods for {@link Enumeration} instances.
29 *
30 * @since 3.0
31 */
32 public class EnumerationUtils {
33
34 /**
35 * Creates an {@link Iterable} that wraps an {@link Enumeration}. The returned {@link Iterable} can be used for a
36 * single iteration.
37 *
38 * @param <T> the element type
39 * @param enumeration the enumeration to use, may not be null
40 * @return a new, single use {@link Iterable}
41 * @since 4.5.0-M1
42 */
43 public static <T> Iterable<T> asIterable(final Enumeration<T> enumeration) {
44 return new IteratorIterable<>(new EnumerationIterator<>(enumeration));
45 }
46
47 /**
48 * Returns the {@code index}-th value in the {@link Enumeration}, throwing
49 * {@code IndexOutOfBoundsException} if there is no such element.
50 * <p>
51 * The Enumeration is advanced to {@code index} (or to the end, if
52 * {@code index} exceeds the number of entries) as a side effect of this method.
53 * </p>
54 *
55 * @param e the enumeration to get a value from
56 * @param index the index to get
57 * @param <T> the type of object in the {@link Enumeration}
58 * @return the object at the specified index
59 * @throws IndexOutOfBoundsException if the index is invalid
60 * @throws IllegalArgumentException if the object type is invalid
61 * @since 4.1
62 */
63 public static <T> T get(final Enumeration<T> e, final int index) {
64 CollectionUtils.checkIndexBounds(index);
65 int i = index;
66 while (e.hasMoreElements()) {
67 i--;
68 if (i == -1) {
69 return e.nextElement();
70 }
71 e.nextElement();
72 }
73 throw new IndexOutOfBoundsException("Entry does not exist: " + i);
74 }
75
76 /**
77 * Creates a list based on an enumeration.
78 *
79 * <p>As the enumeration is traversed, an ArrayList of its values is
80 * created. The new list is returned.</p>
81 *
82 * @param <E> the element type
83 * @param enumeration the enumeration to traverse, which should not be {@code null}.
84 * @return a list containing all elements of the given enumeration
85 * @throws NullPointerException if the enumeration parameter is {@code null}.
86 */
87 public static <E> List<E> toList(final Enumeration<? extends E> enumeration) {
88 return IteratorUtils.toList(new EnumerationIterator<>(enumeration));
89 }
90
91 /**
92 * Override toList(Enumeration) for StringTokenizer as it implements Enumeration<Object>
93 * for the sake of backward compatibility.
94 *
95 * @param stringTokenizer the tokenizer to convert to a {@link List}<{@link String}>
96 * @return a list containing all tokens of the given StringTokenizer
97 */
98 public static List<String> toList(final StringTokenizer stringTokenizer) {
99 final List<String> result = new ArrayList<>(stringTokenizer.countTokens());
100 while (stringTokenizer.hasMoreTokens()) {
101 result.add(stringTokenizer.nextToken());
102 }
103 return result;
104 }
105
106 /**
107 * Don't allow instances.
108 */
109 private EnumerationUtils() {
110 // no instances.
111 }
112
113 }