| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.collections4.iterators; |
| |
| import java.util.Iterator; |
| |
| import org.apache.commons.collections4.ResettableIterator; |
| |
| /** |
| * Adapter to make an {@link Iterator Iterator} instance appear to be an |
| * {@link Iterable Iterable} instance. The iterable can be constructed in one |
| * of two variants: single use, multiple use. |
| * |
| * <p> |
| * In the single use iterable case, the iterable is only usable for one |
| * iterative operation over the source iterator. Subsequent iterative |
| * operations use the same, exhausted source iterator. To create a single use |
| * iterable, construct a new {@link IteratorIterable} using a {@link Iterator} |
| * that is NOT a {@link ResettableIterator} iterator: |
| * </p> |
| * |
| * <pre> |
| * Iterator<Integer> iterator = // some non-resettable iterator |
| * Iterable<Integer> iterable = new IteratorIterable<Integer>(iterator); |
| * </pre> |
| * |
| * <p> |
| * In the multiple use iterable case, the iterable is usable for any number of |
| * iterative operations over the source iterator. Of special note, even though |
| * the iterable supports multiple iterations, it does not support concurrent |
| * iterations. To implicitly create a multiple use iterable, construct a new |
| * {@link IteratorIterable} using a {@link ResettableIterator} iterator: |
| * </p> |
| * |
| * <pre> |
| * Integer[] array = {Integer.valueOf(1),Integer.valueOf(2),Integer.valueOf(3)}; |
| * Iterator<Integer> iterator = IteratorUtils.arrayIterator(array); // a resettable iterator |
| * Iterable<Integer> iterable = new IteratorIterable<Integer>(iterator); |
| * </pre> |
| * |
| * <p> |
| * A multiple use iterable can also be explicitly constructed using any |
| * {@link Iterator} and specifying {@code true} for the |
| * {@code multipleUse} flag: |
| * </p> |
| * |
| * <pre> |
| * Iterator<Integer> iterator = // some non-resettable iterator |
| * Iterable<Integer> iterable = new IteratorIterable<Integer>(iterator, true); |
| * </pre> |
| * |
| * @param <E> the type of elements returned by this iterator. |
| * @since 4.0 |
| */ |
| public class IteratorIterable<E> implements Iterable<E> { |
| |
| /** |
| * Factory method to create an {@link Iterator Iterator} from another |
| * iterator over objects of a different subtype. |
| */ |
| private static <E> Iterator<E> createTypesafeIterator(final Iterator<? extends E> iterator) { |
| return new Iterator<E>() { |
| @Override |
| public boolean hasNext() { |
| return iterator.hasNext(); |
| } |
| |
| @Override |
| public E next() { |
| return iterator.next(); |
| } |
| |
| @Override |
| public void remove() { |
| iterator.remove(); |
| } |
| }; |
| } |
| |
| /** the iterator being adapted into an iterable. */ |
| private final Iterator<? extends E> iterator; |
| |
| /** the iterator parameterized as the {@link #iterator()} return type. */ |
| private final Iterator<E> typeSafeIterator; |
| |
| /** |
| * Constructs a new {@code IteratorIterable} that will use the given |
| * iterator. |
| * |
| * @param iterator the iterator to use. |
| */ |
| public IteratorIterable(final Iterator<? extends E> iterator) { |
| this(iterator, false); |
| } |
| |
| /** |
| * Constructs a new {@code IteratorIterable} that will use the given |
| * iterator. |
| * |
| * @param iterator the iterator to use. |
| * @param multipleUse {@code true} if the new iterable can be used in multiple iterations |
| */ |
| public IteratorIterable(final Iterator<? extends E> iterator, final boolean multipleUse) { |
| if (multipleUse && !(iterator instanceof ResettableIterator)) { |
| this.iterator = new ListIteratorWrapper<>(iterator); |
| } else { |
| this.iterator = iterator; |
| } |
| this.typeSafeIterator = createTypesafeIterator(this.iterator); |
| } |
| |
| /** |
| * Gets the iterator wrapped by this iterable. |
| * |
| * @return the iterator |
| */ |
| @Override |
| public Iterator<E> iterator() { |
| if (iterator instanceof ResettableIterator) { |
| ((ResettableIterator<? extends E>) iterator).reset(); |
| } |
| return typeSafeIterator; |
| } |
| } |