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 2.0 (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      /**
047       * Returns the empty bimap.
048       */
049      // Casting to any type is safe because the set will never hold any elements.
050      @SuppressWarnings("unchecked")
051      public static <K, V> ImmutableBiMap<K, V> of() {
052        return (ImmutableBiMap<K, V>) EmptyImmutableBiMap.INSTANCE;
053      }
054    
055      /**
056       * Returns an immutable bimap containing a single entry.
057       */
058      public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1) {
059        return new RegularImmutableBiMap<K, V>(ImmutableMap.of(k1, v1));
060      }
061    
062      /**
063       * Returns an immutable map containing the given entries, in order.
064       *
065       * @throws IllegalArgumentException if duplicate keys or values are added
066       */
067      public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2) {
068        return new RegularImmutableBiMap<K, V>(ImmutableMap.of(k1, v1, k2, v2));
069      }
070    
071      /**
072       * Returns an immutable map containing the given entries, in order.
073       *
074       * @throws IllegalArgumentException if duplicate keys or values are added
075       */
076      public static <K, V> ImmutableBiMap<K, V> of(
077          K k1, V v1, K k2, V v2, K k3, V v3) {
078        return new RegularImmutableBiMap<K, V>(ImmutableMap.of(
079            k1, v1, k2, v2, k3, v3));
080      }
081    
082      /**
083       * Returns an immutable map containing the given entries, in order.
084       *
085       * @throws IllegalArgumentException if duplicate keys or values are added
086       */
087      public static <K, V> ImmutableBiMap<K, V> of(
088          K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
089        return new RegularImmutableBiMap<K, V>(ImmutableMap.of(
090            k1, v1, k2, v2, k3, v3, k4, v4));
091      }
092    
093      /**
094       * Returns an immutable map containing the given entries, in order.
095       *
096       * @throws IllegalArgumentException if duplicate keys or values are added
097       */
098      public static <K, V> ImmutableBiMap<K, V> of(
099          K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
100        return new RegularImmutableBiMap<K, V>(ImmutableMap.of(
101            k1, v1, k2, v2, k3, v3, k4, v4, k5, v5));
102      }
103    
104      // looking for of() with > 5 entries? Use the builder instead.
105    
106      /**
107       * Returns a new builder. The generated builder is equivalent to the builder
108       * created by the {@link Builder} constructor.
109       */
110      public static <K, V> Builder<K, V> builder() {
111        return new Builder<K, V>();
112      }
113    
114      /**
115       * A builder for creating immutable bimap instances, especially {@code public
116       * static final} bimaps ("constant bimaps"). Example: <pre>   {@code
117       *
118       *   static final ImmutableBiMap<String, Integer> WORD_TO_INT =
119       *       new ImmutableBiMap.Builder<String, Integer>()
120       *           .put("one", 1)
121       *           .put("two", 2)
122       *           .put("three", 3)
123       *           .build();}</pre>
124       *
125       * For <i>small</i> immutable bimaps, the {@code ImmutableBiMap.of()} methods
126       * are even more convenient.
127       *
128       * <p>Builder instances can be reused - it is safe to call {@link #build}
129       * multiple times to build multiple bimaps in series. Each bimap is a superset
130       * of the bimaps created before it.
131       *
132       * @since 2.0 (imported from Google Collections Library)
133       */
134      public static final class Builder<K, V> extends ImmutableMap.Builder<K, V> {
135    
136        /**
137         * Creates a new builder. The returned builder is equivalent to the builder
138         * generated by {@link ImmutableBiMap#builder}.
139         */
140        public Builder() {}
141    
142        /**
143         * Associates {@code key} with {@code value} in the built bimap. Duplicate
144         * keys or values are not allowed, and will cause {@link #build} to fail.
145         */
146        @Override public Builder<K, V> put(K key, V value) {
147          super.put(key, value);
148          return this;
149        }
150    
151        /**
152         * Associates all of the given map's keys and values in the built bimap.
153         * Duplicate keys or values are not allowed, and will cause {@link #build}
154         * to fail.
155         *
156         * @throws NullPointerException if any key or value in {@code map} is null
157         */
158        @Override public Builder<K, V> putAll(Map<? extends K, ? extends V> map) {
159          super.putAll(map);
160          return this;
161        }
162    
163        /**
164         * Returns a newly-created immutable bimap.
165         *
166         * @throws IllegalArgumentException if duplicate keys or values were added
167         */
168        @Override public ImmutableBiMap<K, V> build() {
169          ImmutableMap<K, V> map = super.build();
170          if (map.isEmpty()) {
171            return of();
172          }
173          return new RegularImmutableBiMap<K, V>(map);
174        }
175      }
176    
177      /**
178       * Returns an immutable bimap containing the same entries as {@code map}. If
179       * {@code map} somehow contains entries with duplicate keys (for example, if
180       * it is a {@code SortedMap} whose comparator is not <i>consistent with
181       * equals</i>), the results of this method are undefined.
182       *
183       * <p>Despite the method name, this method attempts to avoid actually copying
184       * the data when it is safe to do so. The exact circumstances under which a
185       * copy will or will not be performed are undocumented and subject to change.
186       *
187       * @throws IllegalArgumentException if two keys have the same value
188       * @throws NullPointerException if any key or value in {@code map} is null
189       */
190      public static <K, V> ImmutableBiMap<K, V> copyOf(
191          Map<? extends K, ? extends V> map) {
192        if (map instanceof ImmutableBiMap) {
193          @SuppressWarnings("unchecked") // safe since map is not writable
194          ImmutableBiMap<K, V> bimap = (ImmutableBiMap<K, V>) map;
195          // TODO(user): if we need to make a copy of a BiMap because the
196          // forward map is a view, don't make a copy of the non-view delegate map
197          if (!bimap.isPartialView()) {
198            return bimap;
199          }
200        }
201    
202        if (map.isEmpty()) {
203          return of();
204        }
205    
206        ImmutableMap<K, V> immutableMap = ImmutableMap.copyOf(map);
207        return new RegularImmutableBiMap<K, V>(immutableMap);
208      }
209    
210      ImmutableBiMap() {}
211    
212      abstract ImmutableMap<K, V> delegate();
213    
214      /**
215       * {@inheritDoc}
216       *
217       * <p>The inverse of an {@code ImmutableBiMap} is another
218       * {@code ImmutableBiMap}.
219       */
220      @Override
221      public abstract ImmutableBiMap<V, K> inverse();
222    
223      @Override public boolean containsKey(@Nullable Object key) {
224        return delegate().containsKey(key);
225      }
226    
227      @Override public boolean containsValue(@Nullable Object value) {
228        return inverse().containsKey(value);
229      }
230    
231      @Override ImmutableSet<Entry<K, V>> createEntrySet() {
232        return delegate().entrySet();
233      }
234    
235      @Override public V get(@Nullable Object key) {
236        return delegate().get(key);
237      }
238    
239      @Override public ImmutableSet<K> keySet() {
240        return delegate().keySet();
241      }
242    
243      /**
244       * Returns an immutable set of the values in this map. The values are in the
245       * same order as the parameters used to build this map.
246       */
247      @Override public ImmutableSet<V> values() {
248        return inverse().keySet();
249      }
250    
251      /**
252       * Guaranteed to throw an exception and leave the bimap unmodified.
253       *
254       * @throws UnsupportedOperationException always
255       */
256      @Override
257      public V forcePut(K key, V value) {
258        throw new UnsupportedOperationException();
259      }
260    
261      @Override public boolean isEmpty() {
262        return delegate().isEmpty();
263      }
264    
265      @Override
266      public int size() {
267        return delegate().size();
268      }
269    
270      @Override public boolean equals(@Nullable Object object) {
271        return object == this || delegate().equals(object);
272      }
273    
274      @Override public int hashCode() {
275        return delegate().hashCode();
276      }
277    
278      @Override public String toString() {
279        return delegate().toString();
280      }
281    
282      /**
283       * Serialized type for all ImmutableBiMap instances. It captures the logical
284       * contents and they are reconstructed using public factory methods. This
285       * ensures that the implementation types remain as implementation details.
286       *
287       * Since the bimap is immutable, ImmutableBiMap doesn't require special logic
288       * for keeping the bimap and its inverse in sync during serialization, the way
289       * AbstractBiMap does.
290       */
291      private static class SerializedForm extends ImmutableMap.SerializedForm {
292        SerializedForm(ImmutableBiMap<?, ?> bimap) {
293          super(bimap);
294        }
295        @Override Object readResolve() {
296          Builder<Object, Object> builder = new Builder<Object, Object>();
297          return createMap(builder);
298        }
299        private static final long serialVersionUID = 0;
300      }
301    
302      @Override Object writeReplace() {
303        return new SerializedForm(this);
304      }
305    }