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        /** 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    }