1 /*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package com.google.common.collect;
18
19 import com.google.common.annotations.GwtCompatible;
20 import com.google.errorprone.annotations.CanIgnoreReturnValue;
21 import java.util.ListIterator;
22
23 /**
24 * A list iterator which forwards all its method calls to another list iterator. Subclasses should
25 * override one or more methods to modify the behavior of the backing iterator as desired per the <a
26 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
27 *
28 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code
29 * default} methods. Specifically, it forwards calls only for methods that existed <a
30 * href="https://docs.oracle.com/javase/7/docs/api/java/util/ListIterator.html">before {@code
31 * default} methods were introduced</a>. For newer methods, like {@code forEachRemaining}, it
32 * inherits their default implementations. When those implementations invoke methods, they invoke
33 * methods on the {@code ForwardingListIterator}.
34 *
35 * @author Mike Bostock
36 * @since 2.0
37 */
38 @GwtCompatible
39 public abstract class ForwardingListIterator<E> extends ForwardingIterator<E>
40 implements ListIterator<E> {
41
42 /** Constructor for use by subclasses. */
43 protected ForwardingListIterator() {}
44
45 @Override
46 protected abstract ListIterator<E> delegate();
47
48 @Override
49 public void add(E element) {
50 delegate().add(element);
51 }
52
53 @Override
54 public boolean hasPrevious() {
55 return delegate().hasPrevious();
56 }
57
58 @Override
59 public int nextIndex() {
60 return delegate().nextIndex();
61 }
62
63 @CanIgnoreReturnValue
64 @Override
65 public E previous() {
66 return delegate().previous();
67 }
68
69 @Override
70 public int previousIndex() {
71 return delegate().previousIndex();
72 }
73
74 @Override
75 public void set(E element) {
76 delegate().set(element);
77 }
78 }