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}