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;
022import org.checkerframework.checker.nullness.qual.Nullable;
023
024/**
025 * A list iterator which forwards all its method calls to another list iterator. Subclasses should
026 * override one or more methods to modify the behavior of the backing iterator as desired per the <a
027 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
028 *
029 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code
030 * default} methods. Specifically, it forwards calls only for methods that existed <a
031 * href="https://docs.oracle.com/javase/7/docs/api/java/util/ListIterator.html">before {@code
032 * default} methods were introduced</a>. For newer methods, like {@code forEachRemaining}, it
033 * inherits their default implementations. When those implementations invoke methods, they invoke
034 * methods on the {@code ForwardingListIterator}.
035 *
036 * @author Mike Bostock
037 * @since 2.0
038 */
039@GwtCompatible
040public abstract class ForwardingListIterator<E extends @Nullable Object>
041    extends ForwardingIterator<E> implements ListIterator<E> {
042
043  /** Constructor for use by subclasses. */
044  protected ForwardingListIterator() {}
045
046  @Override
047  protected abstract ListIterator<E> delegate();
048
049  @Override
050  public void add(@ParametricNullness E element) {
051    delegate().add(element);
052  }
053
054  @Override
055  public boolean hasPrevious() {
056    return delegate().hasPrevious();
057  }
058
059  @Override
060  public int nextIndex() {
061    return delegate().nextIndex();
062  }
063
064  @CanIgnoreReturnValue
065  @Override
066  @ParametricNullness
067  public E previous() {
068    return delegate().previous();
069  }
070
071  @Override
072  public int previousIndex() {
073    return delegate().previousIndex();
074  }
075
076  @Override
077  public void set(@ParametricNullness E element) {
078    delegate().set(element);
079  }
080}