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.iterators;
18
19 import java.util.ListIterator;
20
21 import org.apache.commons.collections4.ResettableListIterator;
22
23 /**
24 * Provides an implementation of an empty list iterator.
25 * <p>
26 * This class provides an implementation of an empty list iterator. This class
27 * provides for binary compatibility between Commons Collections 2.1.1 and 3.1
28 * due to issues with {@code IteratorUtils}.
29 *
30 * @param <E> the type of elements returned by this iterator.
31 * @since 2.1.1 and 3.1
32 */
33 public class EmptyListIterator<E> extends AbstractEmptyIterator<E> implements
34 ResettableListIterator<E> {
35
36 /**
37 * Singleton instance of the iterator.
38 * @since 3.1
39 */
40 @SuppressWarnings("rawtypes")
41 public static final ResettableListIterator RESETTABLE_INSTANCE = new EmptyListIterator<>();
42
43 /**
44 * Singleton instance of the iterator.
45 * @since 2.1.1 and 3.1
46 */
47 @SuppressWarnings("rawtypes")
48 public static final ListIterator INSTANCE = RESETTABLE_INSTANCE;
49
50 /**
51 * Gets a typed instance of the iterator.
52 * @param <E> the element type
53 * @return {@link ListIterator}<E>
54 */
55 public static <E> ListIterator<E> emptyListIterator() {
56 return INSTANCE;
57 }
58
59 /**
60 * Gets a typed instance of the iterator.
61 * @param <E> the element type
62 * @return {@link ResettableListIterator}<E>
63 */
64 public static <E> ResettableListIterator<E> resettableEmptyListIterator() {
65 return RESETTABLE_INSTANCE;
66 }
67
68 /**
69 * Constructs a new instance.
70 */
71 protected EmptyListIterator() {
72 }
73
74 }