001/*
002 * Copyright (C) 2009 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.base.Preconditions.checkNotNull;
020import static java.util.Objects.requireNonNull;
021
022import com.google.common.annotations.GwtCompatible;
023import com.google.common.annotations.GwtIncompatible;
024import com.google.common.annotations.J2ktIncompatible;
025import com.google.common.base.MoreObjects;
026import com.google.errorprone.annotations.CanIgnoreReturnValue;
027import com.google.errorprone.annotations.DoNotCall;
028import com.google.errorprone.annotations.concurrent.LazyInit;
029import com.google.j2objc.annotations.RetainedWith;
030import com.google.j2objc.annotations.Weak;
031import java.io.IOException;
032import java.io.InvalidObjectException;
033import java.io.ObjectInputStream;
034import java.io.ObjectOutputStream;
035import java.util.Arrays;
036import java.util.Collection;
037import java.util.Comparator;
038import java.util.Map;
039import java.util.Map.Entry;
040import javax.annotation.CheckForNull;
041
042/**
043 * A {@link SetMultimap} whose contents will never change, with many other important properties
044 * detailed at {@link ImmutableCollection}.
045 *
046 * <p><b>Warning:</b> As in all {@link SetMultimap}s, do not modify either a key <i>or a value</i>
047 * of a {@code ImmutableSetMultimap} in a way that affects its {@link Object#equals} behavior.
048 * Undefined behavior and bugs will result.
049 *
050 * <p>See the Guava User Guide article on <a href=
051 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained">immutable collections</a>.
052 *
053 * @author Mike Ward
054 * @since 2.0
055 */
056@GwtCompatible(serializable = true, emulated = true)
057@ElementTypesAreNonnullByDefault
058public class ImmutableSetMultimap<K, V> extends ImmutableMultimap<K, V>
059    implements SetMultimap<K, V> {
060
061  /**
062   * Returns the empty multimap.
063   *
064   * <p><b>Performance note:</b> the instance returned is a singleton.
065   */
066  // Casting is safe because the multimap will never hold any elements.
067  @SuppressWarnings("unchecked")
068  public static <K, V> ImmutableSetMultimap<K, V> of() {
069    return (ImmutableSetMultimap<K, V>) EmptyImmutableSetMultimap.INSTANCE;
070  }
071
072  /** Returns an immutable multimap containing a single entry. */
073  public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1) {
074    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
075    builder.put(k1, v1);
076    return builder.build();
077  }
078
079  /**
080   * Returns an immutable multimap containing the given entries, in order. Repeated occurrences of
081   * an entry (according to {@link Object#equals}) after the first are ignored.
082   */
083  public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2) {
084    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
085    builder.put(k1, v1);
086    builder.put(k2, v2);
087    return builder.build();
088  }
089
090  /**
091   * Returns an immutable multimap containing the given entries, in order. Repeated occurrences of
092   * an entry (according to {@link Object#equals}) after the first are ignored.
093   */
094  public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
095    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
096    builder.put(k1, v1);
097    builder.put(k2, v2);
098    builder.put(k3, v3);
099    return builder.build();
100  }
101
102  /**
103   * Returns an immutable multimap containing the given entries, in order. Repeated occurrences of
104   * an entry (according to {@link Object#equals}) after the first are ignored.
105   */
106  public static <K, V> ImmutableSetMultimap<K, V> of(
107      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
108    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
109    builder.put(k1, v1);
110    builder.put(k2, v2);
111    builder.put(k3, v3);
112    builder.put(k4, v4);
113    return builder.build();
114  }
115
116  /**
117   * Returns an immutable multimap containing the given entries, in order. Repeated occurrences of
118   * an entry (according to {@link Object#equals}) after the first are ignored.
119   */
120  public static <K, V> ImmutableSetMultimap<K, V> of(
121      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
122    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
123    builder.put(k1, v1);
124    builder.put(k2, v2);
125    builder.put(k3, v3);
126    builder.put(k4, v4);
127    builder.put(k5, v5);
128    return builder.build();
129  }
130
131  // looking for of() with > 5 entries? Use the builder instead.
132
133  /** Returns a new {@link Builder}. */
134  public static <K, V> Builder<K, V> builder() {
135    return new Builder<>();
136  }
137
138  /**
139   * A builder for creating immutable {@code SetMultimap} instances, especially {@code public static
140   * final} multimaps ("constant multimaps"). Example:
141   *
142   * <pre>{@code
143   * static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP =
144   *     new ImmutableSetMultimap.Builder<String, Integer>()
145   *         .put("one", 1)
146   *         .putAll("several", 1, 2, 3)
147   *         .putAll("many", 1, 2, 3, 4, 5)
148   *         .build();
149   * }</pre>
150   *
151   * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build
152   * multiple multimaps in series. Each multimap contains the key-value mappings in the previously
153   * created multimaps.
154   *
155   * @since 2.0
156   */
157  public static final class Builder<K, V> extends ImmutableMultimap.Builder<K, V> {
158    /**
159     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
160     * ImmutableSetMultimap#builder}.
161     */
162    public Builder() {
163      super();
164    }
165
166    @Override
167    Collection<V> newMutableValueCollection() {
168      return Platform.preservesInsertionOrderOnAddsSet();
169    }
170
171    /** Adds a key-value mapping to the built multimap if it is not already present. */
172    @CanIgnoreReturnValue
173    @Override
174    public Builder<K, V> put(K key, V value) {
175      super.put(key, value);
176      return this;
177    }
178
179    /**
180     * Adds an entry to the built multimap if it is not already present.
181     *
182     * @since 11.0
183     */
184    @CanIgnoreReturnValue
185    @Override
186    public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
187      super.put(entry);
188      return this;
189    }
190
191    /**
192     * {@inheritDoc}
193     *
194     * @since 19.0
195     */
196    @CanIgnoreReturnValue
197    @Override
198    public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) {
199      super.putAll(entries);
200      return this;
201    }
202
203    @CanIgnoreReturnValue
204    @Override
205    public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
206      super.putAll(key, values);
207      return this;
208    }
209
210    @CanIgnoreReturnValue
211    @Override
212    public Builder<K, V> putAll(K key, V... values) {
213      return putAll(key, Arrays.asList(values));
214    }
215
216    @CanIgnoreReturnValue
217    @Override
218    public Builder<K, V> putAll(Multimap<? extends K, ? extends V> multimap) {
219      for (Entry<? extends K, ? extends Collection<? extends V>> entry :
220          multimap.asMap().entrySet()) {
221        putAll(entry.getKey(), entry.getValue());
222      }
223      return this;
224    }
225
226    @CanIgnoreReturnValue
227    @Override
228    Builder<K, V> combine(ImmutableMultimap.Builder<K, V> other) {
229      super.combine(other);
230      return this;
231    }
232
233    /**
234     * {@inheritDoc}
235     *
236     * @since 8.0
237     */
238    @CanIgnoreReturnValue
239    @Override
240    public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) {
241      super.orderKeysBy(keyComparator);
242      return this;
243    }
244
245    /**
246     * Specifies the ordering of the generated multimap's values for each key.
247     *
248     * <p>If this method is called, the sets returned by the {@code get()} method of the generated
249     * multimap and its {@link Multimap#asMap()} view are {@link ImmutableSortedSet} instances.
250     * However, serialization does not preserve that property, though it does maintain the key and
251     * value ordering.
252     *
253     * @since 8.0
254     */
255    // TODO: Make serialization behavior consistent.
256    @CanIgnoreReturnValue
257    @Override
258    public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
259      super.orderValuesBy(valueComparator);
260      return this;
261    }
262
263    /** Returns a newly-created immutable set multimap. */
264    @Override
265    public ImmutableSetMultimap<K, V> build() {
266      Collection<Map.Entry<K, Collection<V>>> mapEntries = builderMap.entrySet();
267      if (keyComparator != null) {
268        mapEntries = Ordering.from(keyComparator).<K>onKeys().immutableSortedCopy(mapEntries);
269      }
270      return fromMapEntries(mapEntries, valueComparator);
271    }
272  }
273
274  /**
275   * Returns an immutable set multimap containing the same mappings as {@code multimap}. The
276   * generated multimap's key and value orderings correspond to the iteration ordering of the {@code
277   * multimap.asMap()} view. Repeated occurrences of an entry in the multimap after the first are
278   * ignored.
279   *
280   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
281   * safe to do so. The exact circumstances under which a copy will or will not be performed are
282   * undocumented and subject to change.
283   *
284   * @throws NullPointerException if any key or value in {@code multimap} is null
285   */
286  public static <K, V> ImmutableSetMultimap<K, V> copyOf(
287      Multimap<? extends K, ? extends V> multimap) {
288    return copyOf(multimap, null);
289  }
290
291  private static <K, V> ImmutableSetMultimap<K, V> copyOf(
292      Multimap<? extends K, ? extends V> multimap,
293      @CheckForNull Comparator<? super V> valueComparator) {
294    checkNotNull(multimap); // eager for GWT
295    if (multimap.isEmpty() && valueComparator == null) {
296      return of();
297    }
298
299    if (multimap instanceof ImmutableSetMultimap) {
300      @SuppressWarnings("unchecked") // safe since multimap is not writable
301      ImmutableSetMultimap<K, V> kvMultimap = (ImmutableSetMultimap<K, V>) multimap;
302      if (!kvMultimap.isPartialView()) {
303        return kvMultimap;
304      }
305    }
306
307    return fromMapEntries(multimap.asMap().entrySet(), valueComparator);
308  }
309
310  /**
311   * Returns an immutable multimap containing the specified entries. The returned multimap iterates
312   * over keys in the order they were first encountered in the input, and the values for each key
313   * are iterated in the order they were encountered. If two values for the same key are {@linkplain
314   * Object#equals equal}, the first value encountered is used.
315   *
316   * @throws NullPointerException if any key, value, or entry is null
317   * @since 19.0
318   */
319  public static <K, V> ImmutableSetMultimap<K, V> copyOf(
320      Iterable<? extends Entry<? extends K, ? extends V>> entries) {
321    return new Builder<K, V>().putAll(entries).build();
322  }
323
324  /** Creates an ImmutableSetMultimap from an asMap.entrySet. */
325  static <K, V> ImmutableSetMultimap<K, V> fromMapEntries(
326      Collection<? extends Map.Entry<? extends K, ? extends Collection<? extends V>>> mapEntries,
327      @CheckForNull Comparator<? super V> valueComparator) {
328    if (mapEntries.isEmpty()) {
329      return of();
330    }
331    ImmutableMap.Builder<K, ImmutableSet<V>> builder =
332        new ImmutableMap.Builder<>(mapEntries.size());
333    int size = 0;
334
335    for (Entry<? extends K, ? extends Collection<? extends V>> entry : mapEntries) {
336      K key = entry.getKey();
337      Collection<? extends V> values = entry.getValue();
338      ImmutableSet<V> set = valueSet(valueComparator, values);
339      if (!set.isEmpty()) {
340        builder.put(key, set);
341        size += set.size();
342      }
343    }
344
345    return new ImmutableSetMultimap<>(builder.buildOrThrow(), size, valueComparator);
346  }
347
348  /**
349   * Returned by get() when a missing key is provided. Also holds the comparator, if any, used for
350   * values.
351   */
352  private final transient ImmutableSet<V> emptySet;
353
354  ImmutableSetMultimap(
355      ImmutableMap<K, ImmutableSet<V>> map,
356      int size,
357      @CheckForNull Comparator<? super V> valueComparator) {
358    super(map, size);
359    this.emptySet = emptySet(valueComparator);
360  }
361
362  // views
363
364  /**
365   * Returns an immutable set of the values for the given key. If no mappings in the multimap have
366   * the provided key, an empty immutable set is returned. The values are in the same order as the
367   * parameters used to build this multimap.
368   */
369  @Override
370  public ImmutableSet<V> get(K key) {
371    // This cast is safe as its type is known in constructor.
372    ImmutableSet<V> set = (ImmutableSet<V>) map.get(key);
373    return MoreObjects.firstNonNull(set, emptySet);
374  }
375
376  @LazyInit @RetainedWith @CheckForNull private transient ImmutableSetMultimap<V, K> inverse;
377
378  /**
379   * {@inheritDoc}
380   *
381   * <p>Because an inverse of a set multimap cannot contain multiple pairs with the same key and
382   * value, this method returns an {@code ImmutableSetMultimap} rather than the {@code
383   * ImmutableMultimap} specified in the {@code ImmutableMultimap} class.
384   */
385  @Override
386  public ImmutableSetMultimap<V, K> inverse() {
387    ImmutableSetMultimap<V, K> result = inverse;
388    return (result == null) ? (inverse = invert()) : result;
389  }
390
391  private ImmutableSetMultimap<V, K> invert() {
392    Builder<V, K> builder = builder();
393    for (Entry<K, V> entry : entries()) {
394      builder.put(entry.getValue(), entry.getKey());
395    }
396    ImmutableSetMultimap<V, K> invertedMultimap = builder.build();
397    invertedMultimap.inverse = this;
398    return invertedMultimap;
399  }
400
401  /**
402   * Guaranteed to throw an exception and leave the multimap unmodified.
403   *
404   * @throws UnsupportedOperationException always
405   * @deprecated Unsupported operation.
406   */
407  @CanIgnoreReturnValue
408  @Deprecated
409  @Override
410  @DoNotCall("Always throws UnsupportedOperationException")
411  public final ImmutableSet<V> removeAll(@CheckForNull Object key) {
412    throw new UnsupportedOperationException();
413  }
414
415  /**
416   * Guaranteed to throw an exception and leave the multimap unmodified.
417   *
418   * @throws UnsupportedOperationException always
419   * @deprecated Unsupported operation.
420   */
421  @CanIgnoreReturnValue
422  @Deprecated
423  @Override
424  @DoNotCall("Always throws UnsupportedOperationException")
425  public final ImmutableSet<V> replaceValues(K key, Iterable<? extends V> values) {
426    throw new UnsupportedOperationException();
427  }
428
429  @LazyInit @RetainedWith @CheckForNull private transient ImmutableSet<Entry<K, V>> entries;
430
431  /**
432   * Returns an immutable collection of all key-value pairs in the multimap. Its iterator traverses
433   * the values for the first key, the values for the second key, and so on.
434   */
435  @Override
436  public ImmutableSet<Entry<K, V>> entries() {
437    ImmutableSet<Entry<K, V>> result = entries;
438    return result == null ? (entries = new EntrySet<>(this)) : result;
439  }
440
441  private static final class EntrySet<K, V> extends ImmutableSet<Entry<K, V>> {
442    @Weak private final transient ImmutableSetMultimap<K, V> multimap;
443
444    EntrySet(ImmutableSetMultimap<K, V> multimap) {
445      this.multimap = multimap;
446    }
447
448    @Override
449    public boolean contains(@CheckForNull Object object) {
450      if (object instanceof Entry) {
451        Entry<?, ?> entry = (Entry<?, ?>) object;
452        return multimap.containsEntry(entry.getKey(), entry.getValue());
453      }
454      return false;
455    }
456
457    @Override
458    public int size() {
459      return multimap.size();
460    }
461
462    @Override
463    public UnmodifiableIterator<Entry<K, V>> iterator() {
464      return multimap.entryIterator();
465    }
466
467    @Override
468    boolean isPartialView() {
469      return false;
470    }
471  }
472
473  private static <V> ImmutableSet<V> valueSet(
474      @CheckForNull Comparator<? super V> valueComparator, Collection<? extends V> values) {
475    return (valueComparator == null)
476        ? ImmutableSet.copyOf(values)
477        : ImmutableSortedSet.copyOf(valueComparator, values);
478  }
479
480  private static <V> ImmutableSet<V> emptySet(@CheckForNull Comparator<? super V> valueComparator) {
481    return (valueComparator == null)
482        ? ImmutableSet.<V>of()
483        : ImmutableSortedSet.<V>emptySet(valueComparator);
484  }
485
486  private static <V> ImmutableSet.Builder<V> valuesBuilder(
487      @CheckForNull Comparator<? super V> valueComparator) {
488    return (valueComparator == null)
489        ? new ImmutableSet.Builder<V>()
490        : new ImmutableSortedSet.Builder<V>(valueComparator);
491  }
492
493  /**
494   * @serialData number of distinct keys, and then for each distinct key: the key, the number of
495   *     values for that key, and the key's values
496   */
497  @GwtIncompatible // java.io.ObjectOutputStream
498  @J2ktIncompatible
499  private void writeObject(ObjectOutputStream stream) throws IOException {
500    stream.defaultWriteObject();
501    stream.writeObject(valueComparator());
502    Serialization.writeMultimap(this, stream);
503  }
504
505  @CheckForNull
506  Comparator<? super V> valueComparator() {
507    return emptySet instanceof ImmutableSortedSet
508        ? ((ImmutableSortedSet<V>) emptySet).comparator()
509        : null;
510  }
511
512  @GwtIncompatible // java serialization
513  @J2ktIncompatible
514  private static final class SetFieldSettersHolder {
515    static final Serialization.FieldSetter<ImmutableSetMultimap> EMPTY_SET_FIELD_SETTER =
516        Serialization.getFieldSetter(ImmutableSetMultimap.class, "emptySet");
517  }
518
519  @GwtIncompatible // java.io.ObjectInputStream
520  @J2ktIncompatible
521  // Serialization type safety is at the caller's mercy.
522  @SuppressWarnings("unchecked")
523  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
524    stream.defaultReadObject();
525    Comparator<Object> valueComparator = (Comparator<Object>) stream.readObject();
526    int keyCount = stream.readInt();
527    if (keyCount < 0) {
528      throw new InvalidObjectException("Invalid key count " + keyCount);
529    }
530    ImmutableMap.Builder<Object, ImmutableSet<Object>> builder = ImmutableMap.builder();
531    int tmpSize = 0;
532
533    for (int i = 0; i < keyCount; i++) {
534      Object key = requireNonNull(stream.readObject());
535      int valueCount = stream.readInt();
536      if (valueCount <= 0) {
537        throw new InvalidObjectException("Invalid value count " + valueCount);
538      }
539
540      ImmutableSet.Builder<Object> valuesBuilder = valuesBuilder(valueComparator);
541      for (int j = 0; j < valueCount; j++) {
542        valuesBuilder.add(requireNonNull(stream.readObject()));
543      }
544      ImmutableSet<Object> valueSet = valuesBuilder.build();
545      if (valueSet.size() != valueCount) {
546        throw new InvalidObjectException("Duplicate key-value pairs exist for key " + key);
547      }
548      builder.put(key, valueSet);
549      tmpSize += valueCount;
550    }
551
552    ImmutableMap<Object, ImmutableSet<Object>> tmpMap;
553    try {
554      tmpMap = builder.buildOrThrow();
555    } catch (IllegalArgumentException e) {
556      throw (InvalidObjectException) new InvalidObjectException(e.getMessage()).initCause(e);
557    }
558
559    FieldSettersHolder.MAP_FIELD_SETTER.set(this, tmpMap);
560    FieldSettersHolder.SIZE_FIELD_SETTER.set(this, tmpSize);
561    SetFieldSettersHolder.EMPTY_SET_FIELD_SETTER.set(this, emptySet(valueComparator));
562  }
563
564  @GwtIncompatible // not needed in emulated source.
565  @J2ktIncompatible
566  private static final long serialVersionUID = 0;
567}