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.Iterator; 20 21 import org.apache.commons.collections4.ResettableIterator; 22 23 /** 24 * Provides an implementation of an empty iterator. 25 * <p> 26 * This class provides an implementation of an empty iterator. 27 * This class provides for binary compatibility between Commons Collections 28 * 2.1.1 and 3.1 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 EmptyIterator<E> extends AbstractEmptyIterator<E> implements ResettableIterator<E> { 34 35 /** 36 * Singleton instance of the iterator. 37 * @since 3.1 38 */ 39 @SuppressWarnings("rawtypes") 40 public static final ResettableIterator RESETTABLE_INSTANCE = new EmptyIterator<>(); 41 42 /** 43 * Singleton instance of the iterator. 44 * @since 2.1.1 and 3.1 45 */ 46 @SuppressWarnings("rawtypes") 47 public static final Iterator INSTANCE = RESETTABLE_INSTANCE; 48 49 /** 50 * Gets a typed empty iterator instance. 51 * @param <E> the element type 52 * @return Iterator<E> 53 */ 54 public static <E> Iterator<E> emptyIterator() { 55 return INSTANCE; 56 } 57 58 /** 59 * Gets a typed resettable empty iterator instance. 60 * @param <E> the element type 61 * @return ResettableIterator<E> 62 */ 63 public static <E> ResettableIterator<E> resettableEmptyIterator() { 64 return RESETTABLE_INSTANCE; 65 } 66 67 /** 68 * Constructs a new instance. 69 */ 70 protected EmptyIterator() { 71 } 72 73 }