1090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson/* 21d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * Copyright (C) 2008 The Guava Authors 3090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 4090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Licensed under the Apache License, Version 2.0 (the "License"); 5090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * you may not use this file except in compliance with the License. 6090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * You may obtain a copy of the License at 7090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 8090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * http://www.apache.org/licenses/LICENSE-2.0 9090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 10090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Unless required by applicable law or agreed to in writing, software 11090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * distributed under the License is distributed on an "AS IS" BASIS, 12090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * See the License for the specific language governing permissions and 14090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * limitations under the License. 15090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 16090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 17090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonpackage com.google.common.collect; 18090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 19090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport com.google.common.annotations.GwtCompatible; 20090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 21090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.Iterator; 22090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonimport java.util.NoSuchElementException; 23090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 24090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson/** 25090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * An iterator that supports a one-element lookahead while iterating. 267dd252788645e940eada959bdde927426e2531c9Paul Duffin * 277dd252788645e940eada959bdde927426e2531c9Paul Duffin * <p>See the Guava User Guide article on <a href= 287dd252788645e940eada959bdde927426e2531c9Paul Duffin * "http://code.google.com/p/guava-libraries/wiki/CollectionHelpersExplained#PeekingIterator"> 297dd252788645e940eada959bdde927426e2531c9Paul Duffin * {@code PeekingIterator}</a>. 30090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 31090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @author Mick Killianey 321d580d0f6ee4f21eb309ba7b509d2c6d671c4044Bjorn Bringert * @since 2.0 (imported from Google Collections Library) 33090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 34090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson@GwtCompatible 35090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilsonpublic interface PeekingIterator<E> extends Iterator<E> { 36090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 37090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * Returns the next element in the iteration, without advancing the iteration. 38090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 39090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Calls to {@code peek()} should not change the state of the iteration, 40090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * except that it <i>may</i> prevent removal of the most recent element via 41090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@link #remove()}. 42090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 43090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws NoSuchElementException if the iteration has no more elements 44090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * according to {@link #hasNext()} 45090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 46090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson E peek(); 47090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 48090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 49090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@inheritDoc} 50090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 51090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>The objects returned by consecutive calls to {@link #peek()} then {@link 52090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * #next()} are guaranteed to be equal to each other. 53090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 540888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 55090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson E next(); 56090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson 57090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson /** 58090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * {@inheritDoc} 59090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 60090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * <p>Implementations may or may not support removal when a call to {@link 61090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * #peek()} has occurred since the most recent call to {@link #next()}. 62090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * 63090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * @throws IllegalStateException if there has been a call to {@link #peek()} 64090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * since the most recent call to {@link #next()} and this implementation 65090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson * does not support this sequence of calls (optional) 66090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson */ 670888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 68090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson void remove(); 69090f9b4c879985bc747c214f82c62471e60c7742Jesse Wilson} 70