1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections4.queue;
18
19 import java.util.Queue;
20
21 import org.apache.commons.collections4.collection.AbstractCollectionDecorator;
22
23 /**
24 * Decorates another {@link Queue} to provide additional behavior.
25 * <p>
26 * Methods are forwarded directly to the decorated queue.
27 * </p>
28 * <p>
29 * This implementation does not forward the hashCode and equals methods through
30 * to the backing object, but relies on Object's implementation. This is
31 * necessary as some Queue implementations, e.g. LinkedList, have a custom
32 * equals implementation for which symmetry cannot be preserved.
33 * See class Javadoc of AbstractCollectionDecorator for more information.
34 * </p>
35 *
36 * @param <E> the type of the elements in the queue
37 * @since 4.0
38 */
39 public abstract class AbstractQueueDecorator<E> extends AbstractCollectionDecorator<E>
40 implements Queue<E> {
41
42 /** Serialization version */
43 private static final long serialVersionUID = -2629815475789577029L;
44
45 /**
46 * Constructor only used in deserialization, do not use otherwise.
47 */
48 protected AbstractQueueDecorator() {
49 }
50
51 /**
52 * Constructor that wraps (not copies).
53 *
54 * @param queue the queue to decorate, must not be null
55 * @throws NullPointerException if queue is null
56 */
57 protected AbstractQueueDecorator(final Queue<E> queue) {
58 super(queue);
59 }
60
61 /**
62 * Gets the queue being decorated.
63 *
64 * @return the decorated queue
65 */
66 @Override
67 protected Queue<E> decorated() {
68 return (Queue<E>) super.decorated();
69 }
70
71 @Override
72 public E element() {
73 return decorated().element();
74 }
75
76 @Override
77 public boolean offer(final E obj) {
78 return decorated().offer(obj);
79 }
80
81 @Override
82 public E peek() {
83 return decorated().peek();
84 }
85
86 @Override
87 public E poll() {
88 return decorated().poll();
89 }
90
91 @Override
92 public E remove() {
93 return decorated().remove();
94 }
95
96 }