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 (imported from Google Collections Library)
050 */
051@GwtCompatible
052public 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    /** Constructor for use by subclasses. */
250    public StandardElementSet() {}
251
252    @Override
253    Multiset<E> multiset() {
254      return ForwardingMultiset.this;
255    }
256  }
257  
258  /**
259   * A sensible definition of {@link #iterator} in terms of {@link #entrySet}
260   * and {@link #remove(Object)}. If you override either of these methods, you
261   * may wish to override {@link #iterator} to forward to this implementation.
262   * 
263   * @since 7.0
264   */
265  @Beta protected Iterator<E> standardIterator() {
266    return Multisets.iteratorImpl(this);
267  }
268
269  /**
270   * A sensible, albeit inefficient, definition of {@link #size} in terms of
271   * {@link #entrySet}. If you override {@link #entrySet}, you may wish to
272   * override {@link #size} to forward to this implementation.
273   * 
274   * @since 7.0
275   */
276  @Beta protected int standardSize() {
277    return Multisets.sizeImpl(this);
278  }
279
280  /**
281   * A sensible, albeit inefficient, definition of {@link #size} in terms of
282   * {@code entrySet().size()} and {@link #count}. If you override either of
283   * these methods, you may wish to override {@link #size} to forward to this
284   * implementation.
285   *
286   * @since 7.0
287   */
288  @Beta protected boolean standardEquals(@Nullable Object object) {
289    return Multisets.equalsImpl(this, object);
290  }
291
292  /**
293   * A sensible definition of {@link #hashCode} as {@code entrySet().hashCode()}
294   * . If you override {@link #entrySet}, you may wish to override {@link
295   * #hashCode} to forward to this implementation.
296   *
297   * @since 7.0
298   */
299  @Beta protected int standardHashCode() {
300    return entrySet().hashCode();
301  }
302
303  /**
304   * A sensible definition of {@link #toString} as {@code entrySet().toString()}
305   * . If you override {@link #entrySet}, you may wish to override {@link
306   * #toString} to forward to this implementation.
307   *
308   * @since 7.0
309   */
310  @Beta @Override protected String standardToString() {
311    return entrySet().toString();
312  }
313}