| /* |
| * Copyright (C) 2008 The Guava Authors |
| * |
| * Licensed 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 com.google.common.collect; |
| |
| import com.google.common.annotations.GwtCompatible; |
| import com.google.errorprone.annotations.CanIgnoreReturnValue; |
| import java.util.Iterator; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * An iterator that supports a one-element lookahead while iterating. |
| * |
| * <p>See the Guava User Guide article on <a href= |
| * "https://github.com/google/guava/wiki/CollectionHelpersExplained#peekingiterator"> {@code |
| * PeekingIterator}</a>. |
| * |
| * @author Mick Killianey |
| * @since 2.0 |
| */ |
| @GwtCompatible |
| public interface PeekingIterator<E> extends Iterator<E> { |
| /** |
| * Returns the next element in the iteration, without advancing the iteration. |
| * |
| * <p>Calls to {@code peek()} should not change the state of the iteration, except that it |
| * <i>may</i> prevent removal of the most recent element via {@link #remove()}. |
| * |
| * @throws NoSuchElementException if the iteration has no more elements according to {@link |
| * #hasNext()} |
| */ |
| E peek(); |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>The objects returned by consecutive calls to {@link #peek()} then {@link #next()} are |
| * guaranteed to be equal to each other. |
| */ |
| @CanIgnoreReturnValue |
| @Override |
| E next(); |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>Implementations may or may not support removal when a call to {@link #peek()} has occurred |
| * since the most recent call to {@link #next()}. |
| * |
| * @throws IllegalStateException if there has been a call to {@link #peek()} since the most recent |
| * call to {@link #next()} and this implementation does not support this sequence of calls |
| * (optional) |
| */ |
| @Override |
| void remove(); |
| } |