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.util.concurrent;
18
19 import com.google.common.annotations.GwtIncompatible;
20 import com.google.common.collect.ForwardingDeque;
21 import java.util.Collection;
22 import java.util.concurrent.BlockingDeque;
23 import java.util.concurrent.TimeUnit;
24 import javax.annotation.CheckForNull;
25
26 /**
27 * A {@link BlockingDeque} which forwards all its method calls to another {@code BlockingDeque}.
28 * Subclasses should override one or more methods to modify the behavior of the backing deque as
29 * desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
30 *
31 * <p><b>Warning:</b> The methods of {@code ForwardingBlockingDeque} forward <b>indiscriminately</b>
32 * to the methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change
33 * the behaviour of {@link #offer} which can lead to unexpected behaviour. In this case, you should
34 * override {@code offer} as well, either providing your own implementation, or delegating to the
35 * provided {@code standardOffer} method.
36 *
37 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
38 * default} methods. Instead, it inherits their default implementations. When those implementations
39 * invoke methods, they invoke methods on the {@code ForwardingBlockingDeque}.
40 *
41 * <p>The {@code standard} methods are not guaranteed to be thread-safe, even when all of the
42 * methods that they depend on are thread-safe.
43 *
44 * @author Emily Soldal
45 * @since 21.0 (since 14.0 as {@link com.google.common.collect.ForwardingBlockingDeque})
46 */
47 @GwtIncompatible
48 @ElementTypesAreNonnullByDefault
49 public abstract class ForwardingBlockingDeque<E> extends ForwardingDeque<E>
50 implements BlockingDeque<E> {
51
52 /** Constructor for use by subclasses. */
53 protected ForwardingBlockingDeque() {}
54
55 @Override
56 protected abstract BlockingDeque<E> delegate();
57
58 @Override
59 public int remainingCapacity() {
60 return delegate().remainingCapacity();
61 }
62
63 @Override
64 public void putFirst(E e) throws InterruptedException {
65 delegate().putFirst(e);
66 }
67
68 @Override
69 public void putLast(E e) throws InterruptedException {
70 delegate().putLast(e);
71 }
72
73 @Override
74 public boolean offerFirst(E e, long timeout, TimeUnit unit) throws InterruptedException {
75 return delegate().offerFirst(e, timeout, unit);
76 }
77
78 @Override
79 public boolean offerLast(E e, long timeout, TimeUnit unit) throws InterruptedException {
80 return delegate().offerLast(e, timeout, unit);
81 }
82
83 @Override
84 public E takeFirst() throws InterruptedException {
85 return delegate().takeFirst();
86 }
87
88 @Override
89 public E takeLast() throws InterruptedException {
90 return delegate().takeLast();
91 }
92
93 @Override
94 @CheckForNull
95 public E pollFirst(long timeout, TimeUnit unit) throws InterruptedException {
96 return delegate().pollFirst(timeout, unit);
97 }
98
99 @Override
100 @CheckForNull
101 public E pollLast(long timeout, TimeUnit unit) throws InterruptedException {
102 return delegate().pollLast(timeout, unit);
103 }
104
105 @Override
106 public void put(E e) throws InterruptedException {
107 delegate().put(e);
108 }
109
110 @Override
111 public boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException {
112 return delegate().offer(e, timeout, unit);
113 }
114
115 @Override
116 public E take() throws InterruptedException {
117 return delegate().take();
118 }
119
120 @Override
121 @CheckForNull
122 public E poll(long timeout, TimeUnit unit) throws InterruptedException {
123 return delegate().poll(timeout, unit);
124 }
125
126 @Override
127 public int drainTo(Collection<? super E> c) {
128 return delegate().drainTo(c);
129 }
130
131 @Override
132 public int drainTo(Collection<? super E> c, int maxElements) {
133 return delegate().drainTo(c, maxElements);
134 }
135 }