001/*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.collect;
018
019import com.google.common.annotations.GwtCompatible;
020import com.google.errorprone.annotations.CanIgnoreReturnValue;
021import java.util.ListIterator;
022
023/**
024 * A list iterator which forwards all its method calls to another list iterator. Subclasses should
025 * override one or more methods to modify the behavior of the backing iterator as desired per the <a
026 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
027 *
028 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code
029 * default} methods. Specifically, it forwards calls only for methods that existed <a
030 * href="https://docs.oracle.com/javase/7/docs/api/java/util/ListIterator.html">before {@code
031 * default} methods were introduced</a>. For newer methods, like {@code forEachRemaining}, it
032 * inherits their default implementations. When those implementations invoke methods, they invoke
033 * methods on the {@code ForwardingListIterator}.
034 *
035 * @author Mike Bostock
036 * @since 2.0
037 */
038@GwtCompatible
039public abstract class ForwardingListIterator<E> extends ForwardingIterator<E>
040    implements ListIterator<E> {
041
042  /** Constructor for use by subclasses. */
043  protected ForwardingListIterator() {}
044
045  @Override
046  protected abstract ListIterator<E> delegate();
047
048  @Override
049  public void add(E element) {
050    delegate().add(element);
051  }
052
053  @Override
054  public boolean hasPrevious() {
055    return delegate().hasPrevious();
056  }
057
058  @Override
059  public int nextIndex() {
060    return delegate().nextIndex();
061  }
062
063  @CanIgnoreReturnValue
064  @Override
065  public E previous() {
066    return delegate().previous();
067  }
068
069  @Override
070  public int previousIndex() {
071    return delegate().previousIndex();
072  }
073
074  @Override
075  public void set(E element) {
076    delegate().set(element);
077  }
078}