001    /*
002     * Copyright (C) 2008 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.GwtCompatible;
020    
021    import java.util.Map;
022    
023    import javax.annotation.Nullable;
024    
025    /**
026     * An immutable {@link BiMap} with reliable user-specified iteration order. Does
027     * not permit null keys or values. An {@code ImmutableBiMap} and its inverse
028     * have the same iteration ordering.
029     *
030     * <p>An instance of {@code ImmutableBiMap} contains its own data and will
031     * <i>never</i> change. {@code ImmutableBiMap} is convenient for
032     * {@code public static final} maps ("constant maps") and also lets you easily
033     * make a "defensive copy" of a bimap provided to your class by a caller.
034     *
035     * <p><b>Note</b>: Although this class is not final, it cannot be subclassed as
036     * it has no public or protected constructors. Thus, instances of this class are
037     * guaranteed to be immutable.
038     *
039     * @author Jared Levy
040     * @since 2 (imported from Google Collections Library)
041     */
042    @GwtCompatible(serializable = true, emulated = true)
043    public abstract class ImmutableBiMap<K, V> extends ImmutableMap<K, V>
044        implements BiMap<K, V> {
045    
046      private static final ImmutableBiMap<Object, Object> EMPTY_IMMUTABLE_BIMAP
047          = new EmptyBiMap();
048    
049      /**
050       * Returns the empty bimap.
051       */
052      // Casting to any type is safe because the set will never hold any elements.
053      @SuppressWarnings("unchecked")
054      public static <K, V> ImmutableBiMap<K, V> of() {
055        return (ImmutableBiMap<K, V>) EMPTY_IMMUTABLE_BIMAP;
056      }
057    
058      /**
059       * Returns an immutable bimap containing a single entry.
060       */
061      public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1) {
062        return new RegularImmutableBiMap<K, V>(ImmutableMap.of(k1, v1));
063      }
064    
065      /**
066       * Returns an immutable map containing the given entries, in order.
067       *
068       * @throws IllegalArgumentException if duplicate keys or values are added
069       */
070      public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2) {
071        return new RegularImmutableBiMap<K, V>(ImmutableMap.of(k1, v1, k2, v2));
072      }
073    
074      /**
075       * Returns an immutable map containing the given entries, in order.
076       *
077       * @throws IllegalArgumentException if duplicate keys or values are added
078       */
079      public static <K, V> ImmutableBiMap<K, V> of(
080          K k1, V v1, K k2, V v2, K k3, V v3) {
081        return new RegularImmutableBiMap<K, V>(ImmutableMap.of(
082            k1, v1, k2, v2, k3, v3));
083      }
084    
085      /**
086       * Returns an immutable map containing the given entries, in order.
087       *
088       * @throws IllegalArgumentException if duplicate keys or values are added
089       */
090      public static <K, V> ImmutableBiMap<K, V> of(
091          K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
092        return new RegularImmutableBiMap<K, V>(ImmutableMap.of(
093            k1, v1, k2, v2, k3, v3, k4, v4));
094      }
095    
096      /**
097       * Returns an immutable map containing the given entries, in order.
098       *
099       * @throws IllegalArgumentException if duplicate keys or values are added
100       */
101      public static <K, V> ImmutableBiMap<K, V> of(
102          K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
103        return new RegularImmutableBiMap<K, V>(ImmutableMap.of(
104            k1, v1, k2, v2, k3, v3, k4, v4, k5, v5));
105      }
106    
107      // looking for of() with > 5 entries? Use the builder instead.
108    
109      /**
110       * Returns a new builder. The generated builder is equivalent to the builder
111       * created by the {@link Builder} constructor.
112       */
113      public static <K, V> Builder<K, V> builder() {
114        return new Builder<K, V>();
115      }
116    
117      /**
118       * A builder for creating immutable bimap instances, especially {@code public
119       * static final} bimaps ("constant bimaps"). Example: <pre>   {@code
120       *
121       *   static final ImmutableBiMap<String, Integer> WORD_TO_INT =
122       *       new ImmutableBiMap.Builder<String, Integer>()
123       *           .put("one", 1)
124       *           .put("two", 2)
125       *           .put("three", 3)
126       *           .build();}</pre>
127       *
128       * For <i>small</i> immutable bimaps, the {@code ImmutableBiMap.of()} methods
129       * are even more convenient.
130       *
131       * <p>Builder instances can be reused - it is safe to call {@link #build}
132       * multiple times to build multiple bimaps in series. Each bimap is a superset
133       * of the bimaps created before it.
134       *
135       * @since 2 (imported from Google Collections Library)
136       */
137      public static final class Builder<K, V> extends ImmutableMap.Builder<K, V> {
138    
139        /**
140         * Creates a new builder. The returned builder is equivalent to the builder
141         * generated by {@link ImmutableBiMap#builder}.
142         */
143        public Builder() {}
144    
145        /**
146         * Associates {@code key} with {@code value} in the built bimap. Duplicate
147         * keys or values are not allowed, and will cause {@link #build} to fail.
148         */
149        @Override public Builder<K, V> put(K key, V value) {
150          super.put(key, value);
151          return this;
152        }
153    
154        /**
155         * Associates all of the given map's keys and values in the built bimap.
156         * Duplicate keys or values are not allowed, and will cause {@link #build}
157         * to fail.
158         *
159         * @throws NullPointerException if any key or value in {@code map} is null
160         */
161        @Override public Builder<K, V> putAll(Map<? extends K, ? extends V> map) {
162          super.putAll(map);
163          return this;
164        }
165    
166        /**
167         * Returns a newly-created immutable bimap.
168         *
169         * @throws IllegalArgumentException if duplicate keys or values were added
170         */
171        @Override public ImmutableBiMap<K, V> build() {
172          ImmutableMap<K, V> map = super.build();
173          if (map.isEmpty()) {
174            return of();
175          }
176          return new RegularImmutableBiMap<K, V>(map);
177        }
178      }
179    
180      /**
181       * Returns an immutable bimap containing the same entries as {@code map}. If
182       * {@code map} somehow contains entries with duplicate keys (for example, if
183       * it is a {@code SortedMap} whose comparator is not <i>consistent with
184       * equals</i>), the results of this method are undefined.
185       *
186       * <p>Despite the method name, this method attempts to avoid actually copying
187       * the data when it is safe to do so. The exact circumstances under which a
188       * copy will or will not be performed are undocumented and subject to change.
189       *
190       * @throws IllegalArgumentException if two keys have the same value
191       * @throws NullPointerException if any key or value in {@code map} is null
192       */
193      public static <K, V> ImmutableBiMap<K, V> copyOf(
194          Map<? extends K, ? extends V> map) {
195        if (map instanceof ImmutableBiMap) {
196          @SuppressWarnings("unchecked") // safe since map is not writable
197          ImmutableBiMap<K, V> bimap = (ImmutableBiMap<K, V>) map;
198          // TODO(user): if we need to make a copy of a BiMap because the
199          // forward map is a view, don't make a copy of the non-view delegate map
200          if (!bimap.isPartialView()) {
201            return bimap;
202          }
203        }
204    
205        if (map.isEmpty()) {
206          return of();
207        }
208    
209        ImmutableMap<K, V> immutableMap = ImmutableMap.copyOf(map);
210        return new RegularImmutableBiMap<K, V>(immutableMap);
211      }
212    
213      ImmutableBiMap() {}
214    
215      abstract ImmutableMap<K, V> delegate();
216    
217      /**
218       * {@inheritDoc}
219       *
220       * <p>The inverse of an {@code ImmutableBiMap} is another
221       * {@code ImmutableBiMap}.
222       */
223      @Override
224      public abstract ImmutableBiMap<V, K> inverse();
225    
226      @Override public boolean containsKey(@Nullable Object key) {
227        return delegate().containsKey(key);
228      }
229    
230      @Override public boolean containsValue(@Nullable Object value) {
231        return inverse().containsKey(value);
232      }
233    
234      @Override public ImmutableSet<Entry<K, V>> entrySet() {
235        return delegate().entrySet();
236      }
237    
238      @Override public V get(@Nullable Object key) {
239        return delegate().get(key);
240      }
241    
242      @Override public ImmutableSet<K> keySet() {
243        return delegate().keySet();
244      }
245    
246      /**
247       * Returns an immutable set of the values in this map. The values are in the
248       * same order as the parameters used to build this map.
249       */
250      @Override public ImmutableSet<V> values() {
251        return inverse().keySet();
252      }
253    
254      /**
255       * Guaranteed to throw an exception and leave the bimap unmodified.
256       *
257       * @throws UnsupportedOperationException always
258       */
259      @Override
260      public V forcePut(K key, V value) {
261        throw new UnsupportedOperationException();
262      }
263    
264      @Override public boolean isEmpty() {
265        return delegate().isEmpty();
266      }
267    
268      @Override
269      public int size() {
270        return delegate().size();
271      }
272    
273      @Override public boolean equals(@Nullable Object object) {
274        return object == this || delegate().equals(object);
275      }
276    
277      @Override public int hashCode() {
278        return delegate().hashCode();
279      }
280    
281      @Override public String toString() {
282        return delegate().toString();
283      }
284    
285      /** Bimap with no mappings. */
286      @SuppressWarnings("serial") // uses writeReplace(), not default serialization
287      static class EmptyBiMap extends ImmutableBiMap<Object, Object> {
288        @Override ImmutableMap<Object, Object> delegate() {
289          return ImmutableMap.of();
290        }
291        @Override public ImmutableBiMap<Object, Object> inverse() {
292          return this;
293        }
294        @Override boolean isPartialView() {
295          return false;
296        }
297        Object readResolve() {
298          return EMPTY_IMMUTABLE_BIMAP; // preserve singleton property
299        }
300      }
301    
302      /**
303       * Serialized type for all ImmutableBiMap instances. It captures the logical
304       * contents and they are reconstructed using public factory methods. This
305       * ensures that the implementation types remain as implementation details.
306       *
307       * Since the bimap is immutable, ImmutableBiMap doesn't require special logic
308       * for keeping the bimap and its inverse in sync during serialization, the way
309       * AbstractBiMap does.
310       */
311      private static class SerializedForm extends ImmutableMap.SerializedForm {
312        SerializedForm(ImmutableBiMap<?, ?> bimap) {
313          super(bimap);
314        }
315        @Override Object readResolve() {
316          Builder<Object, Object> builder = new Builder<Object, Object>();
317          return createMap(builder);
318        }
319        private static final long serialVersionUID = 0;
320      }
321    
322      @Override Object writeReplace() {
323        return new SerializedForm(this);
324      }
325    }