001/* 002 * Copyright (C) 2011 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the 010 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either 011 * express or implied. See the License for the specific language governing permissions and 012 * limitations under the License. 013 */ 014 015package com.google.common.collect; 016 017import com.google.common.annotations.GwtCompatible; 018import java.util.Comparator; 019import java.util.Iterator; 020import java.util.NavigableSet; 021import javax.annotation.CheckForNull; 022import org.checkerframework.checker.nullness.qual.Nullable; 023 024/** 025 * A sorted multiset which forwards all its method calls to another sorted multiset. Subclasses 026 * should override one or more methods to modify the behavior of the backing multiset as desired per 027 * the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 028 * 029 * <p><b>Warning:</b> The methods of {@code ForwardingSortedMultiset} forward 030 * <b>indiscriminately</b> to the methods of the delegate. For example, overriding {@link 031 * #add(Object, int)} alone <b>will not</b> change the behavior of {@link #add(Object)}, which can 032 * lead to unexpected behavior. In this case, you should override {@code add(Object)} as well, 033 * either providing your own implementation, or delegating to the provided {@code standardAdd} 034 * method. 035 * 036 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code 037 * default} methods. Instead, it inherits their default implementations. When those implementations 038 * invoke methods, they invoke methods on the {@code ForwardingSortedMultiset}. 039 * 040 * <p>The {@code standard} methods and any collection views they return are not guaranteed to be 041 * thread-safe, even when all of the methods that they depend on are thread-safe. 042 * 043 * @author Louis Wasserman 044 * @since 15.0 045 */ 046@GwtCompatible(emulated = true) 047@ElementTypesAreNonnullByDefault 048public abstract class ForwardingSortedMultiset<E extends @Nullable Object> 049 extends ForwardingMultiset<E> implements SortedMultiset<E> { 050 /** Constructor for use by subclasses. */ 051 protected ForwardingSortedMultiset() {} 052 053 @Override 054 protected abstract SortedMultiset<E> delegate(); 055 056 @Override 057 public NavigableSet<E> elementSet() { 058 return delegate().elementSet(); 059 } 060 061 /** 062 * A sensible implementation of {@link SortedMultiset#elementSet} in terms of the following 063 * methods: {@link SortedMultiset#clear}, {@link SortedMultiset#comparator}, {@link 064 * SortedMultiset#contains}, {@link SortedMultiset#containsAll}, {@link SortedMultiset#count}, 065 * {@link SortedMultiset#firstEntry} {@link SortedMultiset#headMultiset}, {@link 066 * SortedMultiset#isEmpty}, {@link SortedMultiset#lastEntry}, {@link SortedMultiset#subMultiset}, 067 * {@link SortedMultiset#tailMultiset}, the {@code size()} and {@code iterator()} methods of 068 * {@link SortedMultiset#entrySet}, and {@link SortedMultiset#remove(Object, int)}. In many 069 * situations, you may wish to override {@link SortedMultiset#elementSet} to forward to this 070 * implementation or a subclass thereof. 071 * 072 * @since 15.0 073 */ 074 protected class StandardElementSet extends SortedMultisets.NavigableElementSet<E> { 075 /** Constructor for use by subclasses. */ 076 public StandardElementSet() { 077 super(ForwardingSortedMultiset.this); 078 } 079 } 080 081 @Override 082 public Comparator<? super E> comparator() { 083 return delegate().comparator(); 084 } 085 086 @Override 087 public SortedMultiset<E> descendingMultiset() { 088 return delegate().descendingMultiset(); 089 } 090 091 /** 092 * A skeleton implementation of a descending multiset view. Normally, {@link 093 * #descendingMultiset()} will not reflect any changes you make to the behavior of methods such as 094 * {@link #add(Object)} or {@link #pollFirstEntry}. This skeleton implementation correctly 095 * delegates each of its operations to the appropriate methods of this {@code 096 * ForwardingSortedMultiset}. 097 * 098 * <p>In many cases, you may wish to override {@link #descendingMultiset()} to return an instance 099 * of a subclass of {@code StandardDescendingMultiset}. 100 * 101 * @since 15.0 102 */ 103 protected abstract class StandardDescendingMultiset extends DescendingMultiset<E> { 104 /** Constructor for use by subclasses. */ 105 public StandardDescendingMultiset() {} 106 107 @Override 108 SortedMultiset<E> forwardMultiset() { 109 return ForwardingSortedMultiset.this; 110 } 111 } 112 113 @Override 114 @CheckForNull 115 public Entry<E> firstEntry() { 116 return delegate().firstEntry(); 117 } 118 119 /** 120 * A sensible definition of {@link #firstEntry()} in terms of {@code entrySet().iterator()}. 121 * 122 * <p>If you override {@link #entrySet()}, you may wish to override {@link #firstEntry()} to 123 * forward to this implementation. 124 */ 125 @CheckForNull 126 protected Entry<E> standardFirstEntry() { 127 Iterator<Entry<E>> entryIterator = entrySet().iterator(); 128 if (!entryIterator.hasNext()) { 129 return null; 130 } 131 Entry<E> entry = entryIterator.next(); 132 return Multisets.immutableEntry(entry.getElement(), entry.getCount()); 133 } 134 135 @Override 136 @CheckForNull 137 public Entry<E> lastEntry() { 138 return delegate().lastEntry(); 139 } 140 141 /** 142 * A sensible definition of {@link #lastEntry()} in terms of {@code 143 * descendingMultiset().entrySet().iterator()}. 144 * 145 * <p>If you override {@link #descendingMultiset} or {@link #entrySet()}, you may wish to override 146 * {@link #firstEntry()} to forward to this implementation. 147 */ 148 @CheckForNull 149 protected Entry<E> standardLastEntry() { 150 Iterator<Entry<E>> entryIterator = descendingMultiset().entrySet().iterator(); 151 if (!entryIterator.hasNext()) { 152 return null; 153 } 154 Entry<E> entry = entryIterator.next(); 155 return Multisets.immutableEntry(entry.getElement(), entry.getCount()); 156 } 157 158 @Override 159 @CheckForNull 160 public Entry<E> pollFirstEntry() { 161 return delegate().pollFirstEntry(); 162 } 163 164 /** 165 * A sensible definition of {@link #pollFirstEntry()} in terms of {@code entrySet().iterator()}. 166 * 167 * <p>If you override {@link #entrySet()}, you may wish to override {@link #pollFirstEntry()} to 168 * forward to this implementation. 169 */ 170 @CheckForNull 171 protected Entry<E> standardPollFirstEntry() { 172 Iterator<Entry<E>> entryIterator = entrySet().iterator(); 173 if (!entryIterator.hasNext()) { 174 return null; 175 } 176 Entry<E> entry = entryIterator.next(); 177 entry = Multisets.immutableEntry(entry.getElement(), entry.getCount()); 178 entryIterator.remove(); 179 return entry; 180 } 181 182 @Override 183 @CheckForNull 184 public Entry<E> pollLastEntry() { 185 return delegate().pollLastEntry(); 186 } 187 188 /** 189 * A sensible definition of {@link #pollLastEntry()} in terms of {@code 190 * descendingMultiset().entrySet().iterator()}. 191 * 192 * <p>If you override {@link #descendingMultiset()} or {@link #entrySet()}, you may wish to 193 * override {@link #pollLastEntry()} to forward to this implementation. 194 */ 195 @CheckForNull 196 protected Entry<E> standardPollLastEntry() { 197 Iterator<Entry<E>> entryIterator = descendingMultiset().entrySet().iterator(); 198 if (!entryIterator.hasNext()) { 199 return null; 200 } 201 Entry<E> entry = entryIterator.next(); 202 entry = Multisets.immutableEntry(entry.getElement(), entry.getCount()); 203 entryIterator.remove(); 204 return entry; 205 } 206 207 @Override 208 public SortedMultiset<E> headMultiset(@ParametricNullness E upperBound, BoundType boundType) { 209 return delegate().headMultiset(upperBound, boundType); 210 } 211 212 @Override 213 public SortedMultiset<E> subMultiset( 214 @ParametricNullness E lowerBound, 215 BoundType lowerBoundType, 216 @ParametricNullness E upperBound, 217 BoundType upperBoundType) { 218 return delegate().subMultiset(lowerBound, lowerBoundType, upperBound, upperBoundType); 219 } 220 221 /** 222 * A sensible definition of {@link #subMultiset(Object, BoundType, Object, BoundType)} in terms of 223 * {@link #headMultiset(Object, BoundType) headMultiset} and {@link #tailMultiset(Object, 224 * BoundType) tailMultiset}. 225 * 226 * <p>If you override either of these methods, you may wish to override {@link 227 * #subMultiset(Object, BoundType, Object, BoundType)} to forward to this implementation. 228 */ 229 protected SortedMultiset<E> standardSubMultiset( 230 @ParametricNullness E lowerBound, 231 BoundType lowerBoundType, 232 @ParametricNullness E upperBound, 233 BoundType upperBoundType) { 234 return tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound, upperBoundType); 235 } 236 237 @Override 238 public SortedMultiset<E> tailMultiset(@ParametricNullness E lowerBound, BoundType boundType) { 239 return delegate().tailMultiset(lowerBound, boundType); 240 } 241}