1 /*
2 * Copyright (C) 2010 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.util.concurrent;
16
17 import com.google.common.annotations.GwtIncompatible;
18 import com.google.common.collect.ForwardingQueue;
19 import com.google.errorprone.annotations.CanIgnoreReturnValue;
20 import java.util.Collection;
21 import java.util.concurrent.BlockingQueue;
22 import java.util.concurrent.TimeUnit;
23 import javax.annotation.CheckForNull;
24
25 /**
26 * A {@link BlockingQueue} which forwards all its method calls to another {@link BlockingQueue}.
27 * Subclasses should override one or more methods to modify the behavior of the backing collection
28 * as desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator
29 * pattern</a>.
30 *
31 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
32 * default} methods. Instead, it inherits their default implementations. When those implementations
33 * invoke methods, they invoke methods on the {@code ForwardingBlockingQueue}.
34 *
35 * @author Raimundo Mirisola
36 * @param <E> the type of elements held in this collection
37 * @since 4.0
38 */
39 @CanIgnoreReturnValue // TODO(cpovirk): Consider being more strict.
40 @GwtIncompatible
41 @ElementTypesAreNonnullByDefault
42 public abstract class ForwardingBlockingQueue<E> extends ForwardingQueue<E>
43 implements BlockingQueue<E> {
44
45 /** Constructor for use by subclasses. */
46 protected ForwardingBlockingQueue() {}
47
48 @Override
49 protected abstract BlockingQueue<E> delegate();
50
51 @Override
52 public int drainTo(Collection<? super E> c, int maxElements) {
53 return delegate().drainTo(c, maxElements);
54 }
55
56 @Override
57 public int drainTo(Collection<? super E> c) {
58 return delegate().drainTo(c);
59 }
60
61 @Override
62 public boolean offer(E e, long timeout, TimeUnit unit) throws InterruptedException {
63 return delegate().offer(e, timeout, unit);
64 }
65
66 @Override
67 @CheckForNull
68 public E poll(long timeout, TimeUnit unit) throws InterruptedException {
69 return delegate().poll(timeout, unit);
70 }
71
72 @Override
73 public void put(E e) throws InterruptedException {
74 delegate().put(e);
75 }
76
77 @Override
78 public int remainingCapacity() {
79 return delegate().remainingCapacity();
80 }
81
82 @Override
83 public E take() throws InterruptedException {
84 return delegate().take();
85 }
86 }