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 * </p> 030 * 031 * @param <E> the type of elements returned by this iterator. 032 * @since 2.1.1 and 3.1 033 */ 034public class EmptyListIterator<E> extends AbstractEmptyIterator<E> implements ResettableListIterator<E> { 035 036 /** 037 * Singleton instance of the iterator. 038 * 039 * @since 3.1 040 */ 041 @SuppressWarnings("rawtypes") 042 public static final ResettableListIterator RESETTABLE_INSTANCE = new EmptyListIterator<>(); 043 044 /** 045 * Singleton instance of the iterator. 046 * 047 * @since 2.1.1 and 3.1 048 */ 049 @SuppressWarnings("rawtypes") 050 public static final ListIterator INSTANCE = RESETTABLE_INSTANCE; 051 052 /** 053 * Gets a typed instance of the iterator. 054 * 055 * @param <E> the element type 056 * @return {@link ListIterator}<E> 057 */ 058 public static <E> ListIterator<E> emptyListIterator() { 059 return INSTANCE; 060 } 061 062 /** 063 * Gets a typed instance of the iterator. 064 * 065 * @param <E> the element type 066 * @return {@link ResettableListIterator}<E> 067 */ 068 public static <E> ResettableListIterator<E> resettableEmptyListIterator() { 069 return RESETTABLE_INSTANCE; 070 } 071 072 /** 073 * Constructs a new instance. 074 */ 075 protected EmptyListIterator() { 076 } 077 078}