1 /*
2 * Copyright (C) 2012 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.GwtIncompatible;
20 import com.google.errorprone.annotations.CanIgnoreReturnValue;
21 import java.util.Deque;
22 import java.util.Iterator;
23
24 /**
25 * A deque which forwards all its method calls to another deque. Subclasses should override one or
26 * more methods to modify the behavior of the backing deque as desired per the <a
27 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
28 *
29 * <p><b>Warning:</b> The methods of {@code ForwardingDeque} forward <b>indiscriminately</b> to the
30 * methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change the
31 * behavior of {@link #offer} which can lead to unexpected behavior. In this case, you should
32 * override {@code offer} as well.
33 *
34 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
35 * default} methods. Instead, it inherits their default implementations. When those implementations
36 * invoke methods, they invoke methods on the {@code ForwardingDeque}.
37 *
38 * @author Kurt Alfred Kluever
39 * @since 12.0
40 */
41 @GwtIncompatible
42 public abstract class ForwardingDeque<E> extends ForwardingQueue<E> implements Deque<E> {
43
44 /** Constructor for use by subclasses. */
45 protected ForwardingDeque() {}
46
47 @Override
48 protected abstract Deque<E> delegate();
49
50 @Override
51 public void addFirst(E e) {
52 delegate().addFirst(e);
53 }
54
55 @Override
56 public void addLast(E e) {
57 delegate().addLast(e);
58 }
59
60 @Override
61 public Iterator<E> descendingIterator() {
62 return delegate().descendingIterator();
63 }
64
65 @Override
66 public E getFirst() {
67 return delegate().getFirst();
68 }
69
70 @Override
71 public E getLast() {
72 return delegate().getLast();
73 }
74
75 @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
76 @Override
77 public boolean offerFirst(E e) {
78 return delegate().offerFirst(e);
79 }
80
81 @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
82 @Override
83 public boolean offerLast(E e) {
84 return delegate().offerLast(e);
85 }
86
87 @Override
88 public E peekFirst() {
89 return delegate().peekFirst();
90 }
91
92 @Override
93 public E peekLast() {
94 return delegate().peekLast();
95 }
96
97 @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
98 @Override
99 public E pollFirst() {
100 return delegate().pollFirst();
101 }
102
103 @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
104 @Override
105 public E pollLast() {
106 return delegate().pollLast();
107 }
108
109 @CanIgnoreReturnValue
110 @Override
111 public E pop() {
112 return delegate().pop();
113 }
114
115 @Override
116 public void push(E e) {
117 delegate().push(e);
118 }
119
120 @CanIgnoreReturnValue
121 @Override
122 public E removeFirst() {
123 return delegate().removeFirst();
124 }
125
126 @CanIgnoreReturnValue
127 @Override
128 public E removeLast() {
129 return delegate().removeLast();
130 }
131
132 @CanIgnoreReturnValue
133 @Override
134 public boolean removeFirstOccurrence(Object o) {
135 return delegate().removeFirstOccurrence(o);
136 }
137
138 @CanIgnoreReturnValue
139 @Override
140 public boolean removeLastOccurrence(Object o) {
141 return delegate().removeLastOccurrence(o);
142 }
143 }