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
017package com.google.common.collect;
018
019import com.google.common.annotations.GwtCompatible;
020
021import java.util.Map;
022
023import 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)
043public 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}