1 /*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package com.google.common.collect;
18
19 import com.google.common.annotations.Beta;
20 import com.google.common.annotations.GwtCompatible;
21 import com.google.common.base.Objects;
22
23 import java.util.Collection;
24 import java.util.Iterator;
25 import java.util.Set;
26
27 import javax.annotation.Nullable;
28
29 /**
30 * A multiset which forwards all its method calls to another multiset.
31 * Subclasses should override one or more methods to modify the behavior of the
32 * backing multiset as desired per the <a
33 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
34 *
35 * <p><b>Warning:</b> The methods of {@code ForwardingMultiset} forward
36 * <b>indiscriminately</b> to the methods of the delegate. For example,
37 * overriding {@link #add(Object, int)} alone <b>will not</b> change the
38 * behavior of {@link #add(Object)}, which can lead to unexpected behavior. In
39 * this case, you should override {@code add(Object)} as well, either providing
40 * your own implementation, or delegating to the provided {@code standardAdd}
41 * method.
42 *
43 * <p>The {@code standard} methods and any collection views they return are not
44 * guaranteed to be thread-safe, even when all of the methods that they depend
45 * on are thread-safe.
46 *
47 * @author Kevin Bourrillion
48 * @author Louis Wasserman
49 * @since 2.0 (imported from Google Collections Library)
50 */
51 @GwtCompatible
52 public abstract class ForwardingMultiset<E> extends ForwardingCollection<E>
53 implements Multiset<E> {
54
55 /** Constructor for use by subclasses. */
56 protected ForwardingMultiset() {}
57
58 @Override protected abstract Multiset<E> delegate();
59
60 @Override
61 public int count(Object element) {
62 return delegate().count(element);
63 }
64
65 @Override
66 public int add(E element, int occurrences) {
67 return delegate().add(element, occurrences);
68 }
69
70 @Override
71 public int remove(Object element, int occurrences) {
72 return delegate().remove(element, occurrences);
73 }
74
75 @Override
76 public Set<E> elementSet() {
77 return delegate().elementSet();
78 }
79
80 @Override
81 public Set<Entry<E>> entrySet() {
82 return delegate().entrySet();
83 }
84
85 @Override public boolean equals(@Nullable Object object) {
86 return object == this || delegate().equals(object);
87 }
88
89 @Override public int hashCode() {
90 return delegate().hashCode();
91 }
92
93 @Override
94 public int setCount(E element, int count) {
95 return delegate().setCount(element, count);
96 }
97
98 @Override
99 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 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 protected void standardClear() {
122 Iterators.clear(entrySet().iterator());
123 }
124
125 /**
126 * A sensible, albeit inefficient, definition of {@link #count} in terms of
127 * {@link #entrySet}. If you override {@link #entrySet}, you may wish to
128 * override {@link #count} to forward to this implementation.
129 *
130 * @since 7.0
131 */
132 @Beta protected int standardCount(@Nullable Object object) {
133 for (Entry<?> entry : this.entrySet()) {
134 if (Objects.equal(entry.getElement(), object)) {
135 return entry.getCount();
136 }
137 }
138 return 0;
139 }
140
141 /**
142 * A sensible definition of {@link #add(Object)} in terms of {@link
143 * #add(Object, int)}. If you override {@link #add(Object, int)}, you may
144 * wish to override {@link #add(Object)} to forward to this implementation.
145 *
146 * @since 7.0
147 */
148 protected boolean standardAdd(E element) {
149 add(element, 1);
150 return true;
151 }
152
153 /**
154 * A sensible definition of {@link #addAll(Collection)} in terms of {@link
155 * #add(Object)} and {@link #add(Object, int)}. If you override either of
156 * these methods, you may wish to override {@link #addAll(Collection)} to
157 * forward to this implementation.
158 *
159 * @since 7.0
160 */
161 @Beta @Override protected boolean standardAddAll(
162 Collection<? extends E> elementsToAdd) {
163 return Multisets.addAllImpl(this, elementsToAdd);
164 }
165
166 /**
167 * A sensible definition of {@link #remove(Object)} in terms of {@link
168 * #remove(Object, int)}. If you override {@link #remove(Object, int)}, you
169 * may wish to override {@link #remove(Object)} to forward to this
170 * implementation.
171 *
172 * @since 7.0
173 */
174 @Override protected boolean standardRemove(Object element) {
175 return remove(element, 1) > 0;
176 }
177
178 /**
179 * A sensible definition of {@link #removeAll} in terms of the {@code
180 * removeAll} method of {@link #elementSet}. If you override {@link
181 * #elementSet}, you may wish to override {@link #removeAll} to forward to
182 * this implementation.
183 *
184 * @since 7.0
185 */
186 @Override protected boolean standardRemoveAll(
187 Collection<?> elementsToRemove) {
188 return Multisets.removeAllImpl(this, elementsToRemove);
189 }
190
191 /**
192 * A sensible definition of {@link #retainAll} in terms of the {@code
193 * retainAll} method of {@link #elementSet}. If you override {@link
194 * #elementSet}, you may wish to override {@link #retainAll} to forward to
195 * this implementation.
196 *
197 * @since 7.0
198 */
199 @Override protected boolean standardRetainAll(
200 Collection<?> elementsToRetain) {
201 return Multisets.retainAllImpl(this, elementsToRetain);
202 }
203
204 /**
205 * A sensible definition of {@link #setCount(Object, int)} in terms of {@link
206 * #count(Object)}, {@link #add(Object, int)}, and {@link #remove(Object,
207 * int)}. {@link #entrySet()}. If you override any of these methods, you may
208 * wish to override {@link #setCount(Object, int)} to forward to this
209 * implementation.
210 *
211 * @since 7.0
212 */
213 protected int standardSetCount(E element, int count) {
214 return Multisets.setCountImpl(this, element, count);
215 }
216
217 /**
218 * A sensible definition of {@link #setCount(Object, int, int)} in terms of
219 * {@link #count(Object)} and {@link #setCount(Object, int)}. If you override
220 * either of these methods, you may wish to override {@link #setCount(Object,
221 * int, int)} to forward to this implementation.
222 *
223 * @since 7.0
224 */
225 protected boolean standardSetCount(E element, int oldCount, int newCount) {
226 return Multisets.setCountImpl(this, element, oldCount, newCount);
227 }
228
229 /**
230 * A sensible implementation of {@link Multiset#elementSet} in terms of the
231 * following methods: {@link ForwardingMultiset#clear}, {@link
232 * ForwardingMultiset#contains}, {@link ForwardingMultiset#containsAll},
233 * {@link ForwardingMultiset#count}, {@link ForwardingMultiset#isEmpty}, the
234 * {@link Set#size} and {@link Set#iterator} methods of {@link
235 * ForwardingMultiset#entrySet}, and {@link ForwardingMultiset#remove(Object,
236 * int)}. In many situations, you may wish to override {@link
237 * ForwardingMultiset#elementSet} to forward to this implementation or a
238 * subclass thereof.
239 *
240 * @since 10.0
241 */
242 @Beta
243 protected class StandardElementSet extends Multisets.ElementSet<E> {
244 /** Constructor for use by subclasses. */
245 public StandardElementSet() {}
246
247 @Override
248 Multiset<E> multiset() {
249 return ForwardingMultiset.this;
250 }
251 }
252
253 /**
254 * A sensible definition of {@link #iterator} in terms of {@link #entrySet}
255 * and {@link #remove(Object)}. If you override either of these methods, you
256 * may wish to override {@link #iterator} to forward to this implementation.
257 *
258 * @since 7.0
259 */
260 protected Iterator<E> standardIterator() {
261 return Multisets.iteratorImpl(this);
262 }
263
264 /**
265 * A sensible, albeit inefficient, definition of {@link #size} in terms of
266 * {@link #entrySet}. If you override {@link #entrySet}, you may wish to
267 * override {@link #size} to forward to this implementation.
268 *
269 * @since 7.0
270 */
271 protected int standardSize() {
272 return Multisets.sizeImpl(this);
273 }
274
275 /**
276 * A sensible, albeit inefficient, definition of {@link #size} in terms of
277 * {@code entrySet().size()} and {@link #count}. If you override either of
278 * these methods, you may wish to override {@link #size} to forward to this
279 * implementation.
280 *
281 * @since 7.0
282 */
283 protected boolean standardEquals(@Nullable Object object) {
284 return Multisets.equalsImpl(this, object);
285 }
286
287 /**
288 * A sensible definition of {@link #hashCode} as {@code entrySet().hashCode()}
289 * . If you override {@link #entrySet}, you may wish to override {@link
290 * #hashCode} to forward to this implementation.
291 *
292 * @since 7.0
293 */
294 protected int standardHashCode() {
295 return entrySet().hashCode();
296 }
297
298 /**
299 * A sensible definition of {@link #toString} as {@code entrySet().toString()}
300 * . If you override {@link #entrySet}, you may wish to override {@link
301 * #toString} to forward to this implementation.
302 *
303 * @since 7.0
304 */
305 @Override protected String standardToString() {
306 return entrySet().toString();
307 }
308 }