    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}