001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4.iterators;
018
019import java.util.ListIterator;
020
021import org.apache.commons.collections4.ResettableListIterator;
022
023/**
024 * Provides an implementation of an empty list iterator.
025 * <p>
026 * This class provides an implementation of an empty list iterator. This class
027 * provides for binary compatibility between Commons Collections 2.1.1 and 3.1
028 * due to issues with <code>IteratorUtils</code>.
029 *
030 * @since 2.1.1 and 3.1
031 */
032public class EmptyListIterator<E> extends AbstractEmptyIterator<E> implements
033        ResettableListIterator<E> {
034
035    /**
036     * Singleton instance of the iterator.
037     * @since 3.1
038     */
039    @SuppressWarnings("rawtypes")
040    public static final ResettableListIterator RESETTABLE_INSTANCE = new EmptyListIterator<>();
041
042    /**
043     * Singleton instance of the iterator.
044     * @since 2.1.1 and 3.1
045     */
046    @SuppressWarnings("rawtypes")
047    public static final ListIterator INSTANCE = RESETTABLE_INSTANCE;
048
049    /**
050     * Get a typed instance of the iterator.
051     * @param <E> the element type
052     * @return {@link ResettableListIterator}&lt;E&gt;
053     */
054    @SuppressWarnings("unchecked")
055    public static <E> ResettableListIterator<E> resettableEmptyListIterator() {
056        return RESETTABLE_INSTANCE;
057    }
058
059    /**
060     * Get a typed instance of the iterator.
061     * @param <E> the element type
062     * @return {@link ListIterator}&lt;E&gt;
063     */
064    @SuppressWarnings("unchecked")
065    public static <E> ListIterator<E> emptyListIterator() {
066        return INSTANCE;
067    }
068
069    /**
070     * Constructor.
071     */
072    protected EmptyListIterator() {
073        super();
074    }
075
076}