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 behavior.
025 * <p>
026 * Methods are forwarded directly to the decorated queue.
027 * </p>
028 * <p>
029 * This implementation does not forward the hashCode and equals methods through
030 * to the backing object, but relies on Object's implementation. This is
031 * necessary as some Queue implementations, e.g. LinkedList, have a custom
032 * equals implementation for which symmetry can not be preserved.
033 * See class Javadoc of AbstractCollectionDecorator for more information.
034 * </p>
035 *
036 * @param <E> the type of the elements in the queue
037 * @since 4.0
038 */
039public abstract class AbstractQueueDecorator<E> extends AbstractCollectionDecorator<E>
040        implements Queue<E> {
041
042    /** Serialization version */
043    private static final long serialVersionUID = -2629815475789577029L;
044
045    /**
046     * Constructor only used in deserialization, do not use otherwise.
047     */
048    protected AbstractQueueDecorator() {
049    }
050
051    /**
052     * Constructor that wraps (not copies).
053     *
054     * @param queue  the queue to decorate, must not be null
055     * @throws NullPointerException if queue is null
056     */
057    protected AbstractQueueDecorator(final Queue<E> queue) {
058        super(queue);
059    }
060
061    /**
062     * Gets the queue being decorated.
063     *
064     * @return the decorated queue
065     */
066    @Override
067    protected Queue<E> decorated() {
068        return (Queue<E>) super.decorated();
069    }
070
071    @Override
072    public E element() {
073        return decorated().element();
074    }
075
076    @Override
077    public boolean offer(final E obj) {
078        return decorated().offer(obj);
079    }
080
081    @Override
082    public E peek() {
083        return decorated().peek();
084    }
085
086    @Override
087    public E poll() {
088        return decorated().poll();
089    }
090
091    @Override
092    public E remove() {
093        return decorated().remove();
094    }
095
096}