    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}.
    029 *
    030 * @param <E> the type of elements returned by this iterator.
    031 * @since 2.1.1 and 3.1
    032 */
    033public class EmptyListIterator<E> extends AbstractEmptyIterator<E> implements
    034        ResettableListIterator<E> {
    035
    036    /**
    037     * Singleton instance of the iterator.
    038     * @since 3.1
    039     */
    040    @SuppressWarnings("rawtypes")
    041    public static final ResettableListIterator RESETTABLE_INSTANCE = new EmptyListIterator<>();
    042
    043    /**
    044     * Singleton instance of the iterator.
    045     * @since 2.1.1 and 3.1
    046     */
    047    @SuppressWarnings("rawtypes")
    048    public static final ListIterator INSTANCE = RESETTABLE_INSTANCE;
    049
    050    /**
    051     * Gets a typed instance of the iterator.
    052     * @param <E> the element type
    053     * @return {@link ListIterator}&lt;E&gt;
    054     */
    055    public static <E> ListIterator<E> emptyListIterator() {
    056        return INSTANCE;
    057    }
    058
    059    /**
    060     * Gets a typed instance of the iterator.
    061     * @param <E> the element type
    062     * @return {@link ResettableListIterator}&lt;E&gt;
    063     */
    064    public static <E> ResettableListIterator<E> resettableEmptyListIterator() {
    065        return RESETTABLE_INSTANCE;
    066    }
    067
    068    /**
    069     * Constructs a new instance.
    070     */
    071    protected EmptyListIterator() {
    072    }
    073
    074}