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}