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
017package com.google.common.collect;
018
019import com.google.common.annotations.Beta;
020import com.google.common.annotations.GwtCompatible;
021import com.google.common.base.Objects;
022
023import java.util.Collection;
024import java.util.Iterator;
025import java.util.Set;
026
027import 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
050 */
051@GwtCompatible
052public abstract class ForwardingMultiset<E> extends ForwardingCollection<E> implements Multiset<E> {
053
054  /** Constructor for use by subclasses. */
055  protected ForwardingMultiset() {}
056
057  @Override
058  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
086  public boolean equals(@Nullable Object object) {
087    return object == this || delegate().equals(object);
088  }
089
090  @Override
091  public int hashCode() {
092    return delegate().hashCode();
093  }
094
095  @Override
096  public int setCount(E element, int count) {
097    return delegate().setCount(element, count);
098  }
099
100  @Override
101  public boolean setCount(E element, int oldCount, int newCount) {
102    return delegate().setCount(element, oldCount, newCount);
103  }
104
105  /**
106   * A sensible definition of {@link #contains} in terms of {@link #count}. If
107   * you override {@link #count}, you may wish to override {@link #contains} to
108   * forward to this implementation.
109   *
110   * @since 7.0
111   */
112  @Override
113  protected boolean standardContains(@Nullable Object object) {
114    return count(object) > 0;
115  }
116
117  /**
118   * A sensible definition of {@link #clear} in terms of the {@code iterator}
119   * method of {@link #entrySet}. If you override {@link #entrySet}, you may
120   * wish to override {@link #clear} to forward to this implementation.
121   *
122   * @since 7.0
123   */
124  @Override
125  protected void standardClear() {
126    Iterators.clear(entrySet().iterator());
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
137  protected int standardCount(@Nullable Object object) {
138    for (Entry<?> entry : this.entrySet()) {
139      if (Objects.equal(entry.getElement(), object)) {
140        return entry.getCount();
141      }
142    }
143    return 0;
144  }
145
146  /**
147   * A sensible definition of {@link #add(Object)} in terms of {@link
148   * #add(Object, int)}. If you override {@link #add(Object, int)}, you may
149   * wish to override {@link #add(Object)} to forward to this implementation.
150   *
151   * @since 7.0
152   */
153  protected boolean standardAdd(E element) {
154    add(element, 1);
155    return true;
156  }
157
158  /**
159   * A sensible definition of {@link #addAll(Collection)} in terms of {@link
160   * #add(Object)} and {@link #add(Object, int)}. If you override either of
161   * these methods, you may wish to override {@link #addAll(Collection)} to
162   * forward to this implementation.
163   *
164   * @since 7.0
165   */
166  @Beta
167  @Override
168  protected boolean standardAddAll(Collection<? extends E> elementsToAdd) {
169    return Multisets.addAllImpl(this, elementsToAdd);
170  }
171
172  /**
173   * A sensible definition of {@link #remove(Object)} in terms of {@link
174   * #remove(Object, int)}. If you override {@link #remove(Object, int)}, you
175   * may wish to override {@link #remove(Object)} to forward to this
176   * implementation.
177   *
178   * @since 7.0
179   */
180  @Override
181  protected boolean standardRemove(Object element) {
182    return remove(element, 1) > 0;
183  }
184
185  /**
186   * A sensible definition of {@link #removeAll} in terms of the {@code
187   * removeAll} method of {@link #elementSet}. If you override {@link
188   * #elementSet}, you may wish to override {@link #removeAll} to forward to
189   * this implementation.
190   *
191   * @since 7.0
192   */
193  @Override
194  protected boolean standardRemoveAll(Collection<?> elementsToRemove) {
195    return Multisets.removeAllImpl(this, elementsToRemove);
196  }
197
198  /**
199   * A sensible definition of {@link #retainAll} in terms of the {@code
200   * retainAll} method of {@link #elementSet}. If you override {@link
201   * #elementSet}, you may wish to override {@link #retainAll} to forward to
202   * this implementation.
203   *
204   * @since 7.0
205   */
206  @Override
207  protected boolean standardRetainAll(Collection<?> elementsToRetain) {
208    return Multisets.retainAllImpl(this, elementsToRetain);
209  }
210
211  /**
212   * A sensible definition of {@link #setCount(Object, int)} in terms of {@link
213   * #count(Object)}, {@link #add(Object, int)}, and {@link #remove(Object,
214   * int)}. {@link #entrySet()}. If you override any of these methods, you may
215   * wish to override {@link #setCount(Object, int)} to forward to this
216   * implementation.
217   *
218   * @since 7.0
219   */
220  protected int standardSetCount(E element, int count) {
221    return Multisets.setCountImpl(this, element, count);
222  }
223
224  /**
225   * A sensible definition of {@link #setCount(Object, int, int)} in terms of
226   * {@link #count(Object)} and {@link #setCount(Object, int)}. If you override
227   * either of these methods, you may wish to override {@link #setCount(Object,
228   * int, int)} to forward to this implementation.
229   *
230   * @since 7.0
231   */
232  protected boolean standardSetCount(E element, int oldCount, int newCount) {
233    return Multisets.setCountImpl(this, element, oldCount, newCount);
234  }
235
236  /**
237   * A sensible implementation of {@link Multiset#elementSet} in terms of the
238   * following methods: {@link ForwardingMultiset#clear}, {@link
239   * ForwardingMultiset#contains}, {@link ForwardingMultiset#containsAll},
240   * {@link ForwardingMultiset#count}, {@link ForwardingMultiset#isEmpty}, the
241   * {@link Set#size} and {@link Set#iterator} methods of {@link
242   * ForwardingMultiset#entrySet}, and {@link ForwardingMultiset#remove(Object,
243   * int)}.  In many situations, you may wish to override {@link
244   * ForwardingMultiset#elementSet} to forward to this implementation or a
245   * subclass thereof.
246   *
247   * @since 10.0
248   */
249  @Beta
250  protected class StandardElementSet extends Multisets.ElementSet<E> {
251    /** Constructor for use by subclasses. */
252    public StandardElementSet() {}
253
254    @Override
255    Multiset<E> multiset() {
256      return ForwardingMultiset.this;
257    }
258  }
259
260  /**
261   * A sensible definition of {@link #iterator} in terms of {@link #entrySet}
262   * and {@link #remove(Object)}. If you override either of these methods, you
263   * may wish to override {@link #iterator} to forward to this implementation.
264   *
265   * @since 7.0
266   */
267  protected Iterator<E> standardIterator() {
268    return Multisets.iteratorImpl(this);
269  }
270
271  /**
272   * A sensible, albeit inefficient, definition of {@link #size} in terms of
273   * {@link #entrySet}. If you override {@link #entrySet}, you may wish to
274   * override {@link #size} to forward to this implementation.
275   *
276   * @since 7.0
277   */
278  protected int standardSize() {
279    return Multisets.sizeImpl(this);
280  }
281
282  /**
283   * A sensible, albeit inefficient, definition of {@link #size} in terms of
284   * {@code entrySet().size()} and {@link #count}. If you override either of
285   * these methods, you may wish to override {@link #size} to forward to this
286   * implementation.
287   *
288   * @since 7.0
289   */
290  protected boolean standardEquals(@Nullable Object object) {
291    return Multisets.equalsImpl(this, object);
292  }
293
294  /**
295   * A sensible definition of {@link #hashCode} as {@code entrySet().hashCode()}
296   * . If you override {@link #entrySet}, you may wish to override {@link
297   * #hashCode} to forward to this implementation.
298   *
299   * @since 7.0
300   */
301  protected int standardHashCode() {
302    return entrySet().hashCode();
303  }
304
305  /**
306   * A sensible definition of {@link #toString} as {@code entrySet().toString()}
307   * . If you override {@link #entrySet}, you may wish to override {@link
308   * #toString} to forward to this implementation.
309   *
310   * @since 7.0
311   */
312  @Override
313  protected String standardToString() {
314    return entrySet().toString();
315  }
316}