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 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}