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    import com.google.common.base.Supplier;
023    
024    import java.util.Collection;
025    import java.util.Iterator;
026    import java.util.Map;
027    import java.util.Set;
028    
029    import javax.annotation.Nullable;
030    
031    /**
032     * A map which forwards all its method calls to another map. Subclasses should
033     * override one or more methods to modify the behavior of the backing map as
034     * desired per the <a
035     * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
036     *
037     * <p><i>Warning:</i> The methods of {@code ForwardingMap} forward
038     * <i>indiscriminately</i> to the methods of the delegate. For example,
039     * overriding {@link #put} alone <i>will not</i> change the behavior of {@link
040     * #putAll}, which can lead to unexpected behavior. In this case, you should
041     * override {@code putAll} as well, either providing your own implementation, or
042     * delegating to the provided {@code standardPutAll} method.
043     *
044     * <p>Each of the {@code standard} methods, where appropriate, use {@link
045     * Objects#equal} to test equality for both keys and values. This may not be
046     * the desired behavior for map implementations that use non-standard notions of
047     * key equality, such as a {@code SortedMap} whose comparator is not consistent
048     * with {@code equals}.
049     *
050     * <p>The {@code standard} methods and the collection views they return are not
051     * guaranteed to be thread-safe, even when all of the methods that they depend
052     * on are thread-safe.
053     *
054     * @author Kevin Bourrillion
055     * @author Jared Levy
056     * @author Louis Wasserman
057     * @since 2.0 (imported from Google Collections Library)
058     */
059    @GwtCompatible
060    public abstract class ForwardingMap<K, V> extends ForwardingObject
061        implements Map<K, V> {
062      // TODO(user): identify places where thread safety is actually lost
063    
064      /** Constructor for use by subclasses. */
065      protected ForwardingMap() {}
066    
067      @Override protected abstract Map<K, V> delegate();
068    
069      @Override
070      public int size() {
071        return delegate().size();
072      }
073    
074      @Override
075      public boolean isEmpty() {
076        return delegate().isEmpty();
077      }
078    
079      @Override
080      public V remove(Object object) {
081        return delegate().remove(object);
082      }
083    
084      @Override
085      public void clear() {
086        delegate().clear();
087      }
088    
089      @Override
090      public boolean containsKey(Object key) {
091        return delegate().containsKey(key);
092      }
093    
094      @Override
095      public boolean containsValue(Object value) {
096        return delegate().containsValue(value);
097      }
098    
099      @Override
100      public V get(Object key) {
101        return delegate().get(key);
102      }
103    
104      @Override
105      public V put(K key, V value) {
106        return delegate().put(key, value);
107      }
108    
109      @Override
110      public void putAll(Map<? extends K, ? extends V> map) {
111        delegate().putAll(map);
112      }
113    
114      @Override
115      public Set<K> keySet() {
116        return delegate().keySet();
117      }
118    
119      @Override
120      public Collection<V> values() {
121        return delegate().values();
122      }
123    
124      @Override
125      public Set<Entry<K, V>> entrySet() {
126        return delegate().entrySet();
127      }
128    
129      @Override public boolean equals(@Nullable Object object) {
130        return object == this || delegate().equals(object);
131      }
132    
133      @Override public int hashCode() {
134        return delegate().hashCode();
135      }
136    
137      /**
138       * A sensible definition of {@link #putAll(Map)} in terms of {@link
139       * #put(Object, Object)}. If you override {@link #put(Object, Object)}, you
140       * may wish to override {@link #putAll(Map)} to forward to this
141       * implementation.
142       *
143       * @since 7.0
144       */
145      @Beta protected void standardPutAll(Map<? extends K, ? extends V> map) {
146        Maps.putAllImpl(this, map);
147      }
148    
149      /**
150       * A sensible, albeit inefficient, definition of {@link #remove} in terms of
151       * the {@code iterator} method of {@link #entrySet}. If you override {@link
152       * #entrySet}, you may wish to override {@link #remove} to forward to this
153       * implementation.
154       *
155       * <p>Alternately, you may wish to override {@link #remove} with {@code
156       * keySet().remove}, assuming that approach would not lead to an infinite
157       * loop.
158       *
159       * @since 7.0
160       */
161      @Beta protected V standardRemove(@Nullable Object key) {
162        Iterator<Entry<K, V>> entryIterator = entrySet().iterator();
163        while (entryIterator.hasNext()) {
164          Entry<K, V> entry = entryIterator.next();
165          if (Objects.equal(entry.getKey(), key)) {
166            V value = entry.getValue();
167            entryIterator.remove();
168            return value;
169          }
170        }
171        return null;
172      }
173    
174      /**
175       * A sensible definition of {@link #clear} in terms of the {@code iterator}
176       * method of {@link #entrySet}. In many cases, you may wish to override
177       * {@link #clear} to forward to this implementation.
178       *
179       * @since 7.0
180       */
181      @Beta protected void standardClear() {
182        Iterator<Entry<K, V>> entryIterator = entrySet().iterator();
183        while (entryIterator.hasNext()) {
184          entryIterator.next();
185          entryIterator.remove();
186        }
187      }
188    
189      /**
190       * A sensible definition of {@link #keySet} in terms of the following methods:
191       * {@link #clear}, {@link #containsKey}, {@link #isEmpty}, {@link #remove},
192       * {@link #size}, and the {@code iterator} method of {@link #entrySet}. In
193       * many cases, you may wish to override {@link #keySet} to forward to this
194       * implementation.
195       *
196       * @since 7.0
197       * @deprecated Use the {@code StandardKeySet} constructor instead.  This
198       *             method will be removed from Guava in Guava release 11.0.
199       */
200      @Beta @Deprecated protected Set<K> standardKeySet() {
201        return new StandardKeySet();
202      }
203    
204      /**
205       * A sensible implementation of {@link Map#keySet} in terms of the following
206       * methods: {@link ForwardingMap#clear}, {@link ForwardingMap#containsKey},
207       * {@link ForwardingMap#isEmpty}, {@link ForwardingMap#remove}, {@link
208       * ForwardingMap#size}, and the {@link Set#iterator} method of {@link
209       * ForwardingMap#entrySet}. In many cases, you may wish to override {@link
210       * ForwardingMap#keySet} to forward to this implementation or a subclass
211       * thereof.
212       *
213       * @since 10.0
214       */
215      @Beta
216      protected class StandardKeySet extends Maps.KeySet<K, V> {
217        public StandardKeySet() {}
218    
219        @Override
220        Map<K, V> map() {
221          return ForwardingMap.this;
222        }
223      }
224    
225      /**
226       * A sensible, albeit inefficient, definition of {@link #containsKey} in terms
227       * of the {@code iterator} method of {@link #entrySet}. If you override {@link
228       * #entrySet}, you may wish to override {@link #containsKey} to forward to
229       * this implementation.
230       *
231       * @since 7.0
232       */
233      @Beta protected boolean standardContainsKey(@Nullable Object key) {
234        return Maps.containsKeyImpl(this, key);
235      }
236    
237      /**
238       * A sensible definition of {@link #values} in terms of the following methods:
239       * {@link #clear}, {@link #containsValue}, {@link #isEmpty}, {@link #size},
240       * and the {@code iterator} method of {@link #entrySet}. In many cases, you
241       * may wish to override {@link #values} to forward to this implementation.
242       *
243       * @since 7.0
244       * @deprecated Use the {@code StandardValues} constructor instead.  This
245       *             method will be removed from Guava in Guava release 11.0.
246       */
247      @Beta @Deprecated protected Collection<V> standardValues() {
248        return new StandardValues();
249      }
250    
251      /**
252       * A sensible implementation of {@link Map#values} in terms of the following
253       * methods: {@link ForwardingMap#clear}, {@link ForwardingMap#containsValue},
254       * {@link ForwardingMap#isEmpty}, {@link ForwardingMap#size}, and the {@link
255       * Set#iterator} method of {@link ForwardingMap#entrySet}. In many cases, you
256       * may wish to override {@link ForwardingMap#values} to forward to this
257       * implementation or a subclass thereof.
258       *
259       * @since 10.0
260       */
261      @Beta
262      protected class StandardValues extends Maps.Values<K, V> {
263        public StandardValues() {}
264    
265        @Override
266        Map<K, V> map() {
267          return ForwardingMap.this;
268        }
269      }
270    
271      /**
272       * A sensible definition of {@link #containsValue} in terms of the {@code
273       * iterator} method of {@link #entrySet}. If you override {@link #entrySet},
274       * you may wish to override {@link #containsValue} to forward to this
275       * implementation.
276       *
277       * @since 7.0
278       */
279      @Beta protected boolean standardContainsValue(@Nullable Object value) {
280        return Maps.containsValueImpl(this, value);
281      }
282    
283      /**
284       * A sensible definition of {@link #entrySet} in terms of the specified {@code
285       * Supplier}, which is used to generate iterators over the entry set, and in
286       * terms of the following methods: {@link #clear}, {@link #containsKey},
287       * {@link #get}, {@link #isEmpty}, {@link #remove}, and {@link #size}. In many
288       * cases, you may wish to override {@link #entrySet} to forward to this
289       * implementation.
290       *
291       * @param entryIteratorSupplier A creator for iterators over the entry set.
292       *        Each call to {@code get} must return an iterator that will
293       *        traverse the entire entry set.
294       *
295       * @since 7.0
296       * @deprecated Use {@code StandardEntrySet} instead.  This method will be
297       *             removed from Guava in Guava release 11.0.
298       */
299      @Deprecated @Beta
300       protected Set<Entry<K, V>> standardEntrySet(
301          final Supplier<Iterator<Entry<K, V>>> entryIteratorSupplier) {
302        return new StandardEntrySet() {
303          @Override public Iterator<Map.Entry<K, V>> iterator() {
304            return entryIteratorSupplier.get();
305          }
306        };
307      }
308    
309      /**
310       * A sensible implementation of {@link Map#entrySet} in terms of the following
311       * methods: {@link ForwardingMap#clear}, {@link ForwardingMap#containsKey},
312       * {@link ForwardingMap#get}, {@link ForwardingMap#isEmpty}, {@link
313       * ForwardingMap#remove}, and {@link ForwardingMap#size}. In many cases, you
314       * may wish to override {@link #entrySet} to forward to this implementation
315       * or a subclass thereof.
316       *
317       * @since 10.0
318       */
319      @Beta
320      protected abstract class StandardEntrySet extends Maps.EntrySet<K, V> {
321        public StandardEntrySet() {}
322    
323        @Override
324        Map<K, V> map() {
325          return ForwardingMap.this;
326        }
327      }
328    
329      /**
330       * A sensible definition of {@link #isEmpty} in terms of the {@code iterator}
331       * method of {@link #entrySet}. If you override {@link #entrySet}, you may
332       * wish to override {@link #isEmpty} to forward to this implementation.
333       *
334       * @since 7.0
335       */
336      @Beta protected boolean standardIsEmpty() {
337        return !entrySet().iterator().hasNext();
338      }
339    
340      /**
341       * A sensible definition of {@link #equals} in terms of the {@code equals}
342       * method of {@link #entrySet}. If you override {@link #entrySet}, you may
343       * wish to override {@link #equals} to forward to this implementation.
344       *
345       * @since 7.0
346       */
347      @Beta protected boolean standardEquals(@Nullable Object object) {
348        return Maps.equalsImpl(this, object);
349      }
350    
351      /**
352       * A sensible definition of {@link #hashCode} in terms of the {@code iterator}
353       * method of {@link #entrySet}. If you override {@link #entrySet}, you may
354       * wish to override {@link #hashCode} to forward to this implementation.
355       *
356       * @since 7.0
357       */
358      @Beta protected int standardHashCode() {
359        return Sets.hashCodeImpl(entrySet());
360      }
361    
362      /**
363       * A sensible definition of {@link #toString} in terms of the {@code iterator}
364       * method of {@link #entrySet}. If you override {@link #entrySet}, you may
365       * wish to override {@link #toString} to forward to this implementation.
366       *
367       * @since 7.0
368       */
369      @Beta protected String standardToString() {
370        return Maps.toStringImpl(this);
371      }
372    }