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.Set;
23 import java.util.StringTokenizer;
24
25 import org.apache.commons.collections4.iterators.EnumerationIterator;
26 import org.apache.commons.collections4.iterators.IteratorIterable;
27
28 /**
29 * Provides utility methods for {@link Enumeration} instances.
30 *
31 * @since 3.0
32 */
33 public class EnumerationUtils {
34
35 /**
36 * Creates an {@link Iterable} that wraps an {@link Enumeration}. The returned {@link Iterable} can be used for a
37 * single iteration.
38 *
39 * @param <T> the element type
40 * @param enumeration the enumeration to use, may not be null
41 * @return a new, single use {@link Iterable}
42 * @since 4.5.0-M1
43 */
44 public static <T> Iterable<T> asIterable(final Enumeration<T> enumeration) {
45 return new IteratorIterable<>(new EnumerationIterator<>(enumeration));
46 }
47
48 /**
49 * Gets the {@code index}-th value in the {@link Enumeration}, throwing
50 * {@code IndexOutOfBoundsException} if there is no such element.
51 * <p>
52 * The Enumeration is advanced to {@code index} (or to the end, if
53 * {@code index} exceeds the number of entries) as a side effect of this method.
54 * </p>
55 *
56 * @param e the enumeration to get a value from
57 * @param index the index to get
58 * @param <T> the type of object in the {@link Enumeration}
59 * @return the object at the specified index
60 * @throws IndexOutOfBoundsException if the index is invalid
61 * @throws IllegalArgumentException if the object type is invalid
62 * @since 4.1
63 */
64 public static <T> T get(final Enumeration<T> e, final int index) {
65 CollectionUtils.checkIndexBounds(index);
66 int i = index;
67 while (e.hasMoreElements()) {
68 i--;
69 if (i == -1) {
70 return e.nextElement();
71 }
72 e.nextElement();
73 }
74 throw new IndexOutOfBoundsException("Entry does not exist: " + i);
75 }
76
77 /**
78 * Creates a list based on an enumeration.
79 *
80 * <p>As the enumeration is traversed, an ArrayList of its values is
81 * created. The new list is returned.</p>
82 *
83 * @param <E> the element type
84 * @param enumeration the enumeration to traverse, which should not be {@code null}.
85 * @return a list containing all elements of the given enumeration
86 * @throws NullPointerException if the enumeration parameter is {@code null}.
87 */
88 public static <E> List<E> toList(final Enumeration<? extends E> enumeration) {
89 return IteratorUtils.toList(new EnumerationIterator<>(enumeration));
90 }
91
92 /**
93 * Override toList(Enumeration) for StringTokenizer as it implements Enumeration<Object>
94 * for the sake of backward compatibility.
95 *
96 * @param stringTokenizer the tokenizer to convert to a {@link List}<{@link String}>
97 * @return a list containing all tokens of the given StringTokenizer
98 */
99 public static List<String> toList(final StringTokenizer stringTokenizer) {
100 final List<String> result = new ArrayList<>(stringTokenizer.countTokens());
101 while (stringTokenizer.hasMoreTokens()) {
102 result.add(stringTokenizer.nextToken());
103 }
104 return result;
105 }
106
107 /**
108 * Creates a set based on an enumeration.
109 *
110 * <p>As the enumeration is traversed, an HashSet of its values is
111 * created. The new set is returned.</p>
112 *
113 * @param <E> the element type
114 * @param enumeration the enumeration to traverse, which should not be {@code null}.
115 * @return a set containing all elements of the given enumeration.
116 * @throws NullPointerException if the enumeration parameter is {@code null}.
117 * @since 4.5.0-M4
118 */
119 public static <E> Set<E> toSet(final Enumeration<? extends E> enumeration) {
120 return IteratorUtils.toSet(new EnumerationIterator<>(enumeration));
121 }
122
123 /**
124 * Don't allow instances.
125 */
126 private EnumerationUtils() {
127 // no instances.
128 }
129
130 }