001 /*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package com.google.common.collect;
018
019 import com.google.common.annotations.Beta;
020 import com.google.common.annotations.GwtCompatible;
021 import com.google.common.base.Objects;
022
023 import java.util.Collection;
024 import java.util.Iterator;
025 import java.util.Set;
026
027 import javax.annotation.Nullable;
028
029 /**
030 * A multiset which forwards all its method calls to another multiset.
031 * Subclasses should override one or more methods to modify the behavior of the
032 * backing multiset as desired per the <a
033 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
034 *
035 * <p><b>Warning:</b> The methods of {@code ForwardingMultiset} forward
036 * <b>indiscriminately</b> to the methods of the delegate. For example,
037 * overriding {@link #add(Object, int)} alone <b>will not</b> change the
038 * behavior of {@link #add(Object)}, which can lead to unexpected behavior. In
039 * this case, you should override {@code add(Object)} as well, either providing
040 * your own implementation, or delegating to the provided {@code standardAdd}
041 * method.
042 *
043 * <p>The {@code standard} methods and any collection views they return are not
044 * guaranteed to be thread-safe, even when all of the methods that they depend
045 * on are thread-safe.
046 *
047 * @author Kevin Bourrillion
048 * @author Louis Wasserman
049 * @since 2.0 (imported from Google Collections Library)
050 */
051 @GwtCompatible
052 public abstract class ForwardingMultiset<E> extends ForwardingCollection<E>
053 implements Multiset<E> {
054
055 /** Constructor for use by subclasses. */
056 protected ForwardingMultiset() {}
057
058 @Override protected abstract Multiset<E> delegate();
059
060 @Override
061 public int count(Object element) {
062 return delegate().count(element);
063 }
064
065 @Override
066 public int add(E element, int occurrences) {
067 return delegate().add(element, occurrences);
068 }
069
070 @Override
071 public int remove(Object element, int occurrences) {
072 return delegate().remove(element, occurrences);
073 }
074
075 @Override
076 public Set<E> elementSet() {
077 return delegate().elementSet();
078 }
079
080 @Override
081 public Set<Entry<E>> entrySet() {
082 return delegate().entrySet();
083 }
084
085 @Override public boolean equals(@Nullable Object object) {
086 return object == this || delegate().equals(object);
087 }
088
089 @Override public int hashCode() {
090 return delegate().hashCode();
091 }
092
093 @Override
094 public int setCount(E element, int count) {
095 return delegate().setCount(element, count);
096 }
097
098 @Override
099 public boolean setCount(E element, int oldCount, int newCount) {
100 return delegate().setCount(element, oldCount, newCount);
101 }
102
103 /**
104 * A sensible definition of {@link #contains} in terms of {@link #count}. If
105 * you override {@link #count}, you may wish to override {@link #contains} to
106 * forward to this implementation.
107 *
108 * @since 7.0
109 */
110 @Override @Beta protected boolean standardContains(@Nullable Object object) {
111 return count(object) > 0;
112 }
113
114 /**
115 * A sensible definition of {@link #clear} in terms of the {@code iterator}
116 * method of {@link #entrySet}. If you override {@link #entrySet}, you may
117 * wish to override {@link #clear} to forward to this implementation.
118 *
119 * @since 7.0
120 */
121 @Override @Beta protected void standardClear() {
122 Iterator<Entry<E>> entryIterator = entrySet().iterator();
123 while (entryIterator.hasNext()) {
124 entryIterator.next();
125 entryIterator.remove();
126 }
127 }
128
129 /**
130 * A sensible, albeit inefficient, definition of {@link #count} in terms of
131 * {@link #entrySet}. If you override {@link #entrySet}, you may wish to
132 * override {@link #count} to forward to this implementation.
133 *
134 * @since 7.0
135 */
136 @Beta protected int standardCount(@Nullable Object object) {
137 for (Entry<?> entry : this.entrySet()) {
138 if (Objects.equal(entry.getElement(), object)) {
139 return entry.getCount();
140 }
141 }
142 return 0;
143 }
144
145 /**
146 * A sensible definition of {@link #add(Object)} in terms of {@link
147 * #add(Object, int)}. If you override {@link #add(Object, int)}, you may
148 * wish to override {@link #add(Object)} to forward to this implementation.
149 *
150 * @since 7.0
151 */
152 @Beta protected boolean standardAdd(E element) {
153 add(element, 1);
154 return true;
155 }
156
157 /**
158 * A sensible definition of {@link #addAll(Collection)} in terms of {@link
159 * #add(Object)} and {@link #add(Object, int)}. If you override either of
160 * these methods, you may wish to override {@link #addAll(Collection)} to
161 * forward to this implementation.
162 *
163 * @since 7.0
164 */
165 @Beta @Override protected boolean standardAddAll(
166 Collection<? extends E> elementsToAdd) {
167 return Multisets.addAllImpl(this, elementsToAdd);
168 }
169
170 /**
171 * A sensible definition of {@link #remove(Object)} in terms of {@link
172 * #remove(Object, int)}. If you override {@link #remove(Object, int)}, you
173 * may wish to override {@link #remove(Object)} to forward to this
174 * implementation.
175 *
176 * @since 7.0
177 */
178 @Beta @Override protected boolean standardRemove(Object element) {
179 return remove(element, 1) > 0;
180 }
181
182 /**
183 * A sensible definition of {@link #removeAll} in terms of the {@code
184 * removeAll} method of {@link #elementSet}. If you override {@link
185 * #elementSet}, you may wish to override {@link #removeAll} to forward to
186 * this implementation.
187 *
188 * @since 7.0
189 */
190 @Beta @Override protected boolean standardRemoveAll(
191 Collection<?> elementsToRemove) {
192 return Multisets.removeAllImpl(this, elementsToRemove);
193 }
194
195 /**
196 * A sensible definition of {@link #retainAll} in terms of the {@code
197 * retainAll} method of {@link #elementSet}. If you override {@link
198 * #elementSet}, you may wish to override {@link #retainAll} to forward to
199 * this implementation.
200 *
201 * @since 7.0
202 */
203 @Beta @Override protected boolean standardRetainAll(
204 Collection<?> elementsToRetain) {
205 return Multisets.retainAllImpl(this, elementsToRetain);
206 }
207
208 /**
209 * A sensible definition of {@link #setCount(Object, int)} in terms of {@link
210 * #count(Object)}, {@link #add(Object, int)}, and {@link #remove(Object,
211 * int)}. {@link #entrySet()}. If you override any of these methods, you may
212 * wish to override {@link #setCount(Object, int)} to forward to this
213 * implementation.
214 *
215 * @since 7.0
216 */
217 @Beta protected int standardSetCount(E element, int count) {
218 return Multisets.setCountImpl(this, element, count);
219 }
220
221 /**
222 * A sensible definition of {@link #setCount(Object, int, int)} in terms of
223 * {@link #count(Object)} and {@link #setCount(Object, int)}. If you override
224 * either of these methods, you may wish to override {@link #setCount(Object,
225 * int, int)} to forward to this implementation.
226 *
227 * @since 7.0
228 */
229 @Beta protected boolean standardSetCount(
230 E element, int oldCount, int newCount) {
231 return Multisets.setCountImpl(this, element, oldCount, newCount);
232 }
233
234 /**
235 * A sensible implementation of {@link Multiset#elementSet} in terms of the
236 * following methods: {@link ForwardingMultiset#clear}, {@link
237 * ForwardingMultiset#contains}, {@link ForwardingMultiset#containsAll},
238 * {@link ForwardingMultiset#count}, {@link ForwardingMultiset#isEmpty}, the
239 * {@link Set#size} and {@link Set#iterator} methods of {@link
240 * ForwardingMultiset#entrySet}, and {@link ForwardingMultiset#remove(Object,
241 * int)}. In many situations, you may wish to override {@link
242 * ForwardingMultiset#elementSet} to forward to this implementation or a
243 * subclass thereof.
244 *
245 * @since 10.0
246 */
247 @Beta
248 protected class StandardElementSet extends Multisets.ElementSet<E> {
249 public StandardElementSet() {}
250
251 @Override
252 Multiset<E> multiset() {
253 return ForwardingMultiset.this;
254 }
255 }
256
257 /**
258 * A sensible definition of {@link #iterator} in terms of {@link #entrySet}
259 * and {@link #remove(Object)}. If you override either of these methods, you
260 * may wish to override {@link #iterator} to forward to this implementation.
261 *
262 * @since 7.0
263 */
264 @Beta protected Iterator<E> standardIterator() {
265 return Multisets.iteratorImpl(this);
266 }
267
268 /**
269 * A sensible, albeit inefficient, definition of {@link #size} in terms of
270 * {@link #entrySet}. If you override {@link #entrySet}, you may wish to
271 * override {@link #size} to forward to this implementation.
272 *
273 * @since 7.0
274 */
275 @Beta protected int standardSize() {
276 return Multisets.sizeImpl(this);
277 }
278
279 /**
280 * A sensible, albeit inefficient, definition of {@link #size} in terms of
281 * {@code entrySet().size()} and {@link #count}. If you override either of
282 * these methods, you may wish to override {@link #size} to forward to this
283 * implementation.
284 *
285 * @since 7.0
286 */
287 @Beta protected boolean standardEquals(@Nullable Object object) {
288 return Multisets.equalsImpl(this, object);
289 }
290
291 /**
292 * A sensible definition of {@link #hashCode} as {@code entrySet().hashCode()}
293 * . If you override {@link #entrySet}, you may wish to override {@link
294 * #hashCode} to forward to this implementation.
295 *
296 * @since 7.0
297 */
298 @Beta protected int standardHashCode() {
299 return entrySet().hashCode();
300 }
301
302 /**
303 * A sensible definition of {@link #toString} as {@code entrySet().toString()}
304 * . If you override {@link #entrySet}, you may wish to override {@link
305 * #toString} to forward to this implementation.
306 *
307 * @since 7.0
308 */
309 @Beta @Override protected String standardToString() {
310 return entrySet().toString();
311 }
312 }