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 static com.google.common.collect.CollectPreconditions.checkEntryNotNull;
020import static com.google.common.collect.CollectPreconditions.checkNonnegative;
021
022import com.google.common.annotations.Beta;
023import com.google.common.annotations.GwtCompatible;
024import com.google.errorprone.annotations.CanIgnoreReturnValue;
025import com.google.errorprone.annotations.DoNotCall;
026import java.util.Arrays;
027import java.util.Collection;
028import java.util.Comparator;
029import java.util.Map;
030import javax.annotation.CheckForNull;
031
032/**
033 * A {@link BiMap} whose contents will never change, with many other important properties detailed
034 * at {@link ImmutableCollection}.
035 *
036 * @author Jared Levy
037 * @since 2.0
038 */
039@GwtCompatible(serializable = true, emulated = true)
040@ElementTypesAreNonnullByDefault
041public abstract class ImmutableBiMap<K, V> extends ImmutableMap<K, V> implements BiMap<K, V> {
042
043  /**
044   * Returns the empty bimap.
045   *
046   * <p><b>Performance note:</b> the instance returned is a singleton.
047   */
048  // Casting to any type is safe because the set will never hold any elements.
049  @SuppressWarnings("unchecked")
050  public static <K, V> ImmutableBiMap<K, V> of() {
051    return (ImmutableBiMap<K, V>) RegularImmutableBiMap.EMPTY;
052  }
053
054  /** Returns an immutable bimap containing a single entry. */
055  public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1) {
056    checkEntryNotNull(k1, v1);
057    return new RegularImmutableBiMap<>(new Object[] {k1, v1}, 1);
058  }
059
060  /**
061   * Returns an immutable map containing the given entries, in order.
062   *
063   * @throws IllegalArgumentException if duplicate keys or values are added
064   */
065  public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2) {
066    checkEntryNotNull(k1, v1);
067    checkEntryNotNull(k2, v2);
068    return new RegularImmutableBiMap<K, V>(new Object[] {k1, v1, k2, v2}, 2);
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(K k1, V v1, K k2, V v2, K k3, V v3) {
077    checkEntryNotNull(k1, v1);
078    checkEntryNotNull(k2, v2);
079    checkEntryNotNull(k3, v3);
080    return new RegularImmutableBiMap<K, V>(new Object[] {k1, v1, k2, v2, k3, v3}, 3);
081  }
082
083  /**
084   * Returns an immutable map containing the given entries, in order.
085   *
086   * @throws IllegalArgumentException if duplicate keys or values are added
087   */
088  public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
089    checkEntryNotNull(k1, v1);
090    checkEntryNotNull(k2, v2);
091    checkEntryNotNull(k3, v3);
092    checkEntryNotNull(k4, v4);
093    return new RegularImmutableBiMap<K, V>(new Object[] {k1, v1, k2, v2, k3, v3, k4, v4}, 4);
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    checkEntryNotNull(k1, v1);
104    checkEntryNotNull(k2, v2);
105    checkEntryNotNull(k3, v3);
106    checkEntryNotNull(k4, v4);
107    checkEntryNotNull(k5, v5);
108    return new RegularImmutableBiMap<K, V>(
109        new Object[] {k1, v1, k2, v2, k3, v3, k4, v4, k5, v5}, 5);
110  }
111
112  /**
113   * Returns an immutable map containing the given entries, in order.
114   *
115   * @throws IllegalArgumentException if duplicate keys or values are added
116   * @since 31.0
117   */
118  public static <K, V> ImmutableBiMap<K, V> of(
119      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6) {
120    checkEntryNotNull(k1, v1);
121    checkEntryNotNull(k2, v2);
122    checkEntryNotNull(k3, v3);
123    checkEntryNotNull(k4, v4);
124    checkEntryNotNull(k5, v5);
125    checkEntryNotNull(k6, v6);
126    return new RegularImmutableBiMap<K, V>(
127        new Object[] {k1, v1, k2, v2, k3, v3, k4, v4, k5, v5, k6, v6}, 6);
128  }
129  /**
130   * Returns an immutable map containing the given entries, in order.
131   *
132   * @throws IllegalArgumentException if duplicate keys or values are added
133   * @since 31.0
134   */
135  public static <K, V> ImmutableBiMap<K, V> of(
136      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6, K k7, V v7) {
137    checkEntryNotNull(k1, v1);
138    checkEntryNotNull(k2, v2);
139    checkEntryNotNull(k3, v3);
140    checkEntryNotNull(k4, v4);
141    checkEntryNotNull(k5, v5);
142    checkEntryNotNull(k6, v6);
143    checkEntryNotNull(k7, v7);
144    return new RegularImmutableBiMap<K, V>(
145        new Object[] {k1, v1, k2, v2, k3, v3, k4, v4, k5, v5, k6, v6, k7, v7}, 7);
146  }
147  /**
148   * Returns an immutable map containing the given entries, in order.
149   *
150   * @throws IllegalArgumentException if duplicate keys or values are added
151   * @since 31.0
152   */
153  public static <K, V> ImmutableBiMap<K, V> of(
154      K k1,
155      V v1,
156      K k2,
157      V v2,
158      K k3,
159      V v3,
160      K k4,
161      V v4,
162      K k5,
163      V v5,
164      K k6,
165      V v6,
166      K k7,
167      V v7,
168      K k8,
169      V v8) {
170    checkEntryNotNull(k1, v1);
171    checkEntryNotNull(k2, v2);
172    checkEntryNotNull(k3, v3);
173    checkEntryNotNull(k4, v4);
174    checkEntryNotNull(k5, v5);
175    checkEntryNotNull(k6, v6);
176    checkEntryNotNull(k7, v7);
177    checkEntryNotNull(k8, v8);
178    return new RegularImmutableBiMap<K, V>(
179        new Object[] {k1, v1, k2, v2, k3, v3, k4, v4, k5, v5, k6, v6, k7, v7, k8, v8}, 8);
180  }
181  /**
182   * Returns an immutable map containing the given entries, in order.
183   *
184   * @throws IllegalArgumentException if duplicate keys or values are added
185   * @since 31.0
186   */
187  public static <K, V> ImmutableBiMap<K, V> of(
188      K k1,
189      V v1,
190      K k2,
191      V v2,
192      K k3,
193      V v3,
194      K k4,
195      V v4,
196      K k5,
197      V v5,
198      K k6,
199      V v6,
200      K k7,
201      V v7,
202      K k8,
203      V v8,
204      K k9,
205      V v9) {
206    checkEntryNotNull(k1, v1);
207    checkEntryNotNull(k2, v2);
208    checkEntryNotNull(k3, v3);
209    checkEntryNotNull(k4, v4);
210    checkEntryNotNull(k5, v5);
211    checkEntryNotNull(k6, v6);
212    checkEntryNotNull(k7, v7);
213    checkEntryNotNull(k8, v8);
214    checkEntryNotNull(k9, v9);
215    return new RegularImmutableBiMap<K, V>(
216        new Object[] {k1, v1, k2, v2, k3, v3, k4, v4, k5, v5, k6, v6, k7, v7, k8, v8, k9, v9}, 9);
217  }
218  /**
219   * Returns an immutable map containing the given entries, in order.
220   *
221   * @throws IllegalArgumentException if duplicate keys or values are added
222   * @since 31.0
223   */
224  public static <K, V> ImmutableBiMap<K, V> of(
225      K k1,
226      V v1,
227      K k2,
228      V v2,
229      K k3,
230      V v3,
231      K k4,
232      V v4,
233      K k5,
234      V v5,
235      K k6,
236      V v6,
237      K k7,
238      V v7,
239      K k8,
240      V v8,
241      K k9,
242      V v9,
243      K k10,
244      V v10) {
245    checkEntryNotNull(k1, v1);
246    checkEntryNotNull(k2, v2);
247    checkEntryNotNull(k3, v3);
248    checkEntryNotNull(k4, v4);
249    checkEntryNotNull(k5, v5);
250    checkEntryNotNull(k6, v6);
251    checkEntryNotNull(k7, v7);
252    checkEntryNotNull(k8, v8);
253    checkEntryNotNull(k9, v9);
254    checkEntryNotNull(k10, v10);
255    return new RegularImmutableBiMap<K, V>(
256        new Object[] {
257          k1, v1, k2, v2, k3, v3, k4, v4, k5, v5, k6, v6, k7, v7, k8, v8, k9, v9, k10, v10
258        },
259        10);
260  }
261
262  // looking for of() with > 10 entries? Use the builder or ofEntries instead.
263
264  /**
265   * Returns an immutable map containing the given entries, in order.
266   *
267   * @throws IllegalArgumentException if duplicate keys or values are provided
268   * @since 31.0
269   */
270  @SafeVarargs
271  public static <K, V> ImmutableBiMap<K, V> ofEntries(Entry<? extends K, ? extends V>... entries) {
272    @SuppressWarnings("unchecked") // we will only ever read these
273    Entry<K, V>[] entries2 = (Entry<K, V>[]) entries;
274    return copyOf(Arrays.asList(entries2));
275  }
276
277  /**
278   * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
279   * Builder} constructor.
280   */
281  public static <K, V> Builder<K, V> builder() {
282    return new Builder<>();
283  }
284
285  /**
286   * Returns a new builder, expecting the specified number of entries to be added.
287   *
288   * <p>If {@code expectedSize} is exactly the number of entries added to the builder before {@link
289   * Builder#build} is called, the builder is likely to perform better than an unsized {@link
290   * #builder()} would have.
291   *
292   * <p>It is not specified if any performance benefits apply if {@code expectedSize} is close to,
293   * but not exactly, the number of entries added to the builder.
294   *
295   * @since 23.1
296   */
297  @Beta
298  public static <K, V> Builder<K, V> builderWithExpectedSize(int expectedSize) {
299    checkNonnegative(expectedSize, "expectedSize");
300    return new Builder<>(expectedSize);
301  }
302
303  /**
304   * A builder for creating immutable bimap instances, especially {@code public static final} bimaps
305   * ("constant bimaps"). Example:
306   *
307   * <pre>{@code
308   * static final ImmutableBiMap<String, Integer> WORD_TO_INT =
309   *     new ImmutableBiMap.Builder<String, Integer>()
310   *         .put("one", 1)
311   *         .put("two", 2)
312   *         .put("three", 3)
313   *         .buildOrThrow();
314   * }</pre>
315   *
316   * <p>For <i>small</i> immutable bimaps, the {@code ImmutableBiMap.of()} methods are even more
317   * convenient.
318   *
319   * <p>By default, a {@code Builder} will generate bimaps that iterate over entries in the order
320   * they were inserted into the builder. For example, in the above example, {@code
321   * WORD_TO_INT.entrySet()} is guaranteed to iterate over the entries in the order {@code "one"=1,
322   * "two"=2, "three"=3}, and {@code keySet()} and {@code values()} respect the same order. If you
323   * want a different order, consider using {@link #orderEntriesByValue(Comparator)}, which changes
324   * this builder to sort entries by value.
325   *
326   * <p>Builder instances can be reused - it is safe to call {@link #buildOrThrow} multiple times to
327   * build multiple bimaps in series. Each bimap is a superset of the bimaps created before it.
328   *
329   * @since 2.0
330   */
331  public static final class Builder<K, V> extends ImmutableMap.Builder<K, V> {
332    /**
333     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
334     * ImmutableBiMap#builder}.
335     */
336    public Builder() {
337      super();
338    }
339
340    Builder(int size) {
341      super(size);
342    }
343
344    /**
345     * Associates {@code key} with {@code value} in the built bimap. Duplicate keys or values are
346     * not allowed, and will cause {@link #build} to fail.
347     */
348    @CanIgnoreReturnValue
349    @Override
350    public Builder<K, V> put(K key, V value) {
351      super.put(key, value);
352      return this;
353    }
354
355    /**
356     * Adds the given {@code entry} to the bimap. Duplicate keys or values are not allowed, and will
357     * cause {@link #build} to fail.
358     *
359     * @since 19.0
360     */
361    @CanIgnoreReturnValue
362    @Override
363    public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
364      super.put(entry);
365      return this;
366    }
367
368    /**
369     * Associates all of the given map's keys and values in the built bimap. Duplicate keys or
370     * values are not allowed, and will cause {@link #build} to fail.
371     *
372     * @throws NullPointerException if any key or value in {@code map} is null
373     */
374    @CanIgnoreReturnValue
375    @Override
376    public Builder<K, V> putAll(Map<? extends K, ? extends V> map) {
377      super.putAll(map);
378      return this;
379    }
380
381    /**
382     * Adds all of the given entries to the built bimap. Duplicate keys or values are not allowed,
383     * and will cause {@link #build} to fail.
384     *
385     * @throws NullPointerException if any key, value, or entry is null
386     * @since 19.0
387     */
388    @CanIgnoreReturnValue
389    @Beta
390    @Override
391    public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) {
392      super.putAll(entries);
393      return this;
394    }
395
396    /**
397     * Configures this {@code Builder} to order entries by value according to the specified
398     * comparator.
399     *
400     * <p>The sort order is stable, that is, if two entries have values that compare as equivalent,
401     * the entry that was inserted first will be first in the built map's iteration order.
402     *
403     * @throws IllegalStateException if this method was already called
404     * @since 19.0
405     */
406    @CanIgnoreReturnValue
407    @Beta
408    @Override
409    public Builder<K, V> orderEntriesByValue(Comparator<? super V> valueComparator) {
410      super.orderEntriesByValue(valueComparator);
411      return this;
412    }
413
414    @Override
415    @CanIgnoreReturnValue
416    Builder<K, V> combine(ImmutableMap.Builder<K, V> builder) {
417      super.combine(builder);
418      return this;
419    }
420
421    /**
422     * Returns a newly-created immutable bimap. The iteration order of the returned bimap is the
423     * order in which entries were inserted into the builder, unless {@link #orderEntriesByValue}
424     * was called, in which case entries are sorted by value.
425     *
426     * <p>Prefer the equivalent method {@link #buildOrThrow()} to make it explicit that the method
427     * will throw an exception if there are duplicate keys or values. The {@code build()} method
428     * will soon be deprecated.
429     *
430     * @throws IllegalArgumentException if duplicate keys or values were added
431     */
432    @Override
433    public ImmutableBiMap<K, V> build() {
434      return buildOrThrow();
435    }
436
437    /**
438     * Returns a newly-created immutable bimap, or throws an exception if any key or value was added
439     * more than once. The iteration order of the returned bimap is the order in which entries were
440     * inserted into the builder, unless {@link #orderEntriesByValue} was called, in which case
441     * entries are sorted by value.
442     *
443     * @throws IllegalArgumentException if duplicate keys or values were added
444     * @since 31.0
445     */
446    @Override
447    public ImmutableBiMap<K, V> buildOrThrow() {
448      if (size == 0) {
449        return of();
450      }
451      sortEntries();
452      entriesUsed = true;
453      return new RegularImmutableBiMap<K, V>(alternatingKeysAndValues, size);
454    }
455  }
456
457  /**
458   * Returns an immutable bimap containing the same entries as {@code map}. If {@code map} somehow
459   * contains entries with duplicate keys (for example, if it is a {@code SortedMap} whose
460   * comparator is not <i>consistent with equals</i>), the results of this method are undefined.
461   *
462   * <p>The returned {@code BiMap} iterates over entries in the same order as the {@code entrySet}
463   * of the original map.
464   *
465   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
466   * safe to do so. The exact circumstances under which a copy will or will not be performed are
467   * undocumented and subject to change.
468   *
469   * @throws IllegalArgumentException if two keys have the same value or two values have the same
470   *     key
471   * @throws NullPointerException if any key or value in {@code map} is null
472   */
473  public static <K, V> ImmutableBiMap<K, V> copyOf(Map<? extends K, ? extends V> map) {
474    if (map instanceof ImmutableBiMap) {
475      @SuppressWarnings("unchecked") // safe since map is not writable
476      ImmutableBiMap<K, V> bimap = (ImmutableBiMap<K, V>) map;
477      // TODO(lowasser): if we need to make a copy of a BiMap because the
478      // forward map is a view, don't make a copy of the non-view delegate map
479      if (!bimap.isPartialView()) {
480        return bimap;
481      }
482    }
483    return copyOf(map.entrySet());
484  }
485
486  /**
487   * Returns an immutable bimap containing the given entries. The returned bimap iterates over
488   * entries in the same order as the original iterable.
489   *
490   * @throws IllegalArgumentException if two keys have the same value or two values have the same
491   *     key
492   * @throws NullPointerException if any key, value, or entry is null
493   * @since 19.0
494   */
495  @Beta
496  public static <K, V> ImmutableBiMap<K, V> copyOf(
497      Iterable<? extends Entry<? extends K, ? extends V>> entries) {
498    int estimatedSize =
499        (entries instanceof Collection)
500            ? ((Collection<?>) entries).size()
501            : ImmutableCollection.Builder.DEFAULT_INITIAL_CAPACITY;
502    return new Builder<K, V>(estimatedSize).putAll(entries).build();
503  }
504
505  ImmutableBiMap() {}
506
507  /**
508   * {@inheritDoc}
509   *
510   * <p>The inverse of an {@code ImmutableBiMap} is another {@code ImmutableBiMap}.
511   */
512  @Override
513  public abstract ImmutableBiMap<V, K> inverse();
514
515  /**
516   * Returns an immutable set of the values in this map, in the same order they appear in {@link
517   * #entrySet}.
518   */
519  @Override
520  public ImmutableSet<V> values() {
521    return inverse().keySet();
522  }
523
524  @Override
525  final ImmutableSet<V> createValues() {
526    throw new AssertionError("should never be called");
527  }
528
529  /**
530   * Guaranteed to throw an exception and leave the bimap unmodified.
531   *
532   * @throws UnsupportedOperationException always
533   * @deprecated Unsupported operation.
534   */
535  @CanIgnoreReturnValue
536  @Deprecated
537  @Override
538  @DoNotCall("Always throws UnsupportedOperationException")
539  @CheckForNull
540  public final V forcePut(K key, V value) {
541    throw new UnsupportedOperationException();
542  }
543
544  /**
545   * Serialized type for all ImmutableBiMap instances. It captures the logical contents and they are
546   * reconstructed using public factory methods. This ensures that the implementation types remain
547   * as implementation details.
548   *
549   * <p>Since the bimap is immutable, ImmutableBiMap doesn't require special logic for keeping the
550   * bimap and its inverse in sync during serialization, the way AbstractBiMap does.
551   */
552  private static class SerializedForm<K, V> extends ImmutableMap.SerializedForm<K, V> {
553    SerializedForm(ImmutableBiMap<K, V> bimap) {
554      super(bimap);
555    }
556
557    @Override
558    Builder<K, V> makeBuilder(int size) {
559      return new Builder<>(size);
560    }
561
562    private static final long serialVersionUID = 0;
563  }
564
565  @Override
566  Object writeReplace() {
567    return new SerializedForm<>(this);
568  }
569}