001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4.queue;
018
019import java.util.Queue;
020
021import org.apache.commons.collections4.collection.AbstractCollectionDecorator;
022
023/**
024 * Decorates another {@link Queue} to provide additional behaviour.
025 * <p>
026 * Methods are forwarded directly to the decorated queue.
027 * <p>
028 * This implementation does not forward the hashCode and equals methods through
029 * to the backing object, but relies on Object's implementation. This is
030 * necessary as some Queue implementations, e.g. LinkedList, have custom a
031 * equals implementation for which symmetry can not be preserved.
032 * See class javadoc of AbstractCollectionDecorator for more information.
033 *
034 * @param <E> the type of the elements in the queue
035 * @since 4.0
036 */
037public abstract class AbstractQueueDecorator<E> extends AbstractCollectionDecorator<E>
038        implements Queue<E> {
039
040    /** Serialization version */
041    private static final long serialVersionUID = -2629815475789577029L;
042
043    /**
044     * Constructor only used in deserialization, do not use otherwise.
045     */
046    protected AbstractQueueDecorator() {
047        super();
048    }
049
050    /**
051     * Constructor that wraps (not copies).
052     *
053     * @param queue  the queue to decorate, must not be null
054     * @throws NullPointerException if queue is null
055     */
056    protected AbstractQueueDecorator(final Queue<E> queue) {
057        super(queue);
058    }
059
060    /**
061     * Gets the queue being decorated.
062     *
063     * @return the decorated queue
064     */
065    @Override
066    protected Queue<E> decorated() {
067        return (Queue<E>) super.decorated();
068    }
069
070    //-----------------------------------------------------------------------
071
072    @Override
073    public boolean offer(final E obj) {
074        return decorated().offer(obj);
075    }
076
077    @Override
078    public E poll() {
079        return decorated().poll();
080    }
081
082    @Override
083    public E peek() {
084        return decorated().peek();
085    }
086
087    @Override
088    public E element() {
089        return decorated().element();
090    }
091
092    @Override
093    public E remove() {
094        return decorated().remove();
095    }
096
097}