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.collection; 018 019import java.io.Serializable; 020import java.util.Collection; 021import java.util.Iterator; 022 023/** 024 * Decorates another <code>Collection</code> to provide additional behaviour. 025 * <p> 026 * Each method call made on this <code>Collection</code> is forwarded to the 027 * decorated <code>Collection</code>. This class is used as a framework on which 028 * to build to extensions such as synchronized and unmodifiable behaviour. The 029 * main advantage of decoration is that one decorator can wrap any implementation 030 * of <code>Collection</code>, whereas sub-classing requires a new class to be 031 * written for each implementation. 032 * <p> 033 * This implementation does not perform any special processing with 034 * {@link #iterator()}. Instead it simply returns the value from the 035 * wrapped collection. This may be undesirable, for example if you are trying 036 * to write an unmodifiable implementation it might provide a loophole. 037 * 038 * @param <E> the type of the elements in the collection 039 * @since 3.0 040 * @version $Id: AbstractCollectionDecorator.html 972421 2015-11-14 20:00:04Z tn $ 041 */ 042public abstract class AbstractCollectionDecorator<E> 043 implements Collection<E>, Serializable { 044 045 /** Serialization version */ 046 private static final long serialVersionUID = 6249888059822088500L; 047 048 /** The collection being decorated */ 049 private Collection<E> collection; 050 051 /** 052 * Constructor only used in deserialization, do not use otherwise. 053 * @since 3.1 054 */ 055 protected AbstractCollectionDecorator() { 056 super(); 057 } 058 059 /** 060 * Constructor that wraps (not copies). 061 * 062 * @param coll the collection to decorate, must not be null 063 * @throws IllegalArgumentException if the collection is null 064 */ 065 protected AbstractCollectionDecorator(final Collection<E> coll) { 066 if (coll == null) { 067 throw new IllegalArgumentException("Collection must not be null"); 068 } 069 this.collection = coll; 070 } 071 072 /** 073 * Gets the collection being decorated. 074 * All access to the decorated collection goes via this method. 075 * 076 * @return the decorated collection 077 */ 078 protected Collection<E> decorated() { 079 return collection; 080 } 081 082 /** 083 * Sets the collection being decorated. 084 * <p> 085 * <b>NOTE:</b> this method should only be used during deserialization 086 * 087 * @param coll the decorated collection 088 */ 089 protected void setCollection(final Collection<E> coll) { 090 this.collection = coll; 091 } 092 093 //----------------------------------------------------------------------- 094 095 public boolean add(final E object) { 096 return decorated().add(object); 097 } 098 099 public boolean addAll(final Collection<? extends E> coll) { 100 return decorated().addAll(coll); 101 } 102 103 public void clear() { 104 decorated().clear(); 105 } 106 107 public boolean contains(final Object object) { 108 return decorated().contains(object); 109 } 110 111 public boolean isEmpty() { 112 return decorated().isEmpty(); 113 } 114 115 public Iterator<E> iterator() { 116 return decorated().iterator(); 117 } 118 119 public boolean remove(final Object object) { 120 return decorated().remove(object); 121 } 122 123 public int size() { 124 return decorated().size(); 125 } 126 127 public Object[] toArray() { 128 return decorated().toArray(); 129 } 130 131 public <T> T[] toArray(final T[] object) { 132 return decorated().toArray(object); 133 } 134 135 public boolean containsAll(final Collection<?> coll) { 136 return decorated().containsAll(coll); 137 } 138 139 public boolean removeAll(final Collection<?> coll) { 140 return decorated().removeAll(coll); 141 } 142 143 public boolean retainAll(final Collection<?> coll) { 144 return decorated().retainAll(coll); 145 } 146 147 @Override 148 public boolean equals(final Object object) { 149 return object == this || decorated().equals(object); 150 } 151 152 @Override 153 public int hashCode() { 154 return decorated().hashCode(); 155 } 156 157 @Override 158 public String toString() { 159 return decorated().toString(); 160 } 161 162}