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.base.Preconditions.checkNotNull;
020
021import com.google.common.annotations.Beta;
022import com.google.common.annotations.GwtCompatible;
023import com.google.common.annotations.GwtIncompatible;
024import com.google.common.base.Preconditions;
025import com.google.errorprone.annotations.CanIgnoreReturnValue;
026import com.google.errorprone.annotations.concurrent.LazyInit;
027import com.google.j2objc.annotations.RetainedWith;
028import java.io.IOException;
029import java.io.InvalidObjectException;
030import java.io.ObjectInputStream;
031import java.io.ObjectOutputStream;
032import java.util.Collection;
033import java.util.Comparator;
034import java.util.Map.Entry;
035import java.util.function.Function;
036import java.util.stream.Collector;
037import java.util.stream.Collectors;
038import java.util.stream.Stream;
039import javax.annotation.Nullable;
040
041/**
042 * A {@link ListMultimap} whose contents will never change, with many other important properties
043 * detailed at {@link ImmutableCollection}.
044 *
045 * <p>See the Guava User Guide article on <a href=
046 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained">
047 * immutable collections</a>.
048 *
049 * @author Jared Levy
050 * @since 2.0
051 */
052@GwtCompatible(serializable = true, emulated = true)
053public class ImmutableListMultimap<K, V> extends ImmutableMultimap<K, V>
054    implements ListMultimap<K, V> {
055  /**
056   * Returns a {@link Collector} that accumulates elements into an {@code ImmutableListMultimap}
057   * whose keys and values are the result of applying the provided mapping functions to the input
058   * elements.
059   *
060   * <p>For streams with {@linkplain java.util.stream#Ordering defined encounter order}, that order
061   * is preserved, but entries are {@linkplain ImmutableMultimap#iteration grouped by key}.
062   *
063   * Example:
064   * <pre>   {@code
065   *
066   *   static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
067   *       Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
068   *           .collect(toImmutableListMultimap(str -> str.charAt(0), str -> str.substring(1)));
069   *
070   *   // is equivalent to
071   *
072   *   static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
073   *       new ImmutableListMultimap.Builder<Character, String>()
074   *           .put('b', "anana")
075   *           .putAll('a', "pple", "sparagus")
076   *           .putAll('c', "arrot", "herry")
077   *           .build();}</pre>
078   *
079   * @since 21.0
080   */
081  @Beta
082  public static <T, K, V> Collector<T, ?, ImmutableListMultimap<K, V>> toImmutableListMultimap(
083      Function<? super T, ? extends K> keyFunction,
084      Function<? super T, ? extends V> valueFunction) {
085    checkNotNull(keyFunction, "keyFunction");
086    checkNotNull(valueFunction, "valueFunction");
087    return Collector.of(
088        ImmutableListMultimap::<K, V>builder,
089        (builder, t) -> builder.put(keyFunction.apply(t), valueFunction.apply(t)),
090        ImmutableListMultimap.Builder::combine,
091        ImmutableListMultimap.Builder::build);
092  }
093  
094  /**
095   * Returns a {@code Collector} accumulating entries into an {@code ImmutableListMultimap}. Each
096   * input element is mapped to a key and a stream of values, each of which are put into the
097   * resulting {@code Multimap}, in the encounter order of the stream and the encounter order of the
098   * streams of values.
099   *
100   * <p>Example:
101   *
102   * <pre>{@code
103   * static final ImmutableListMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
104   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
105   *         .collect(
106   *             flatteningToImmutableListMultimap(
107   *                  str -> str.charAt(0),
108   *                  str -> str.substring(1).chars().mapToObj(c -> (char) c));
109   *
110   * // is equivalent to
111   *
112   * static final ImmutableListMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
113   *     ImmutableListMultimap.<Character, Character>builder()
114   *         .putAll('b', Arrays.asList('a', 'n', 'a', 'n', 'a'))
115   *         .putAll('a', Arrays.asList('p', 'p', 'l', 'e'))
116   *         .putAll('c', Arrays.asList('a', 'r', 'r', 'o', 't'))
117   *         .putAll('a', Arrays.asList('s', 'p', 'a', 'r', 'a', 'g', 'u', 's'))
118   *         .putAll('c', Arrays.asList('h', 'e', 'r', 'r', 'y'))
119   *         .build();
120   * }
121   * }</pre>
122   *
123   * @since 21.0
124   */
125  @Beta
126  public static <T, K, V>
127      Collector<T, ?, ImmutableListMultimap<K, V>> flatteningToImmutableListMultimap(
128          Function<? super T, ? extends K> keyFunction,
129          Function<? super T, ? extends Stream<? extends V>> valuesFunction) {
130    checkNotNull(keyFunction);
131    checkNotNull(valuesFunction);
132    return Collectors.collectingAndThen(
133        Multimaps.flatteningToMultimap(
134            input -> checkNotNull(keyFunction.apply(input)),
135            input -> valuesFunction.apply(input).peek(Preconditions::checkNotNull),
136            MultimapBuilder.linkedHashKeys().arrayListValues()::<K, V>build),
137        ImmutableListMultimap::copyOf);
138  }
139
140  /** Returns the empty multimap. */
141  // Casting is safe because the multimap will never hold any elements.
142  @SuppressWarnings("unchecked")
143  public static <K, V> ImmutableListMultimap<K, V> of() {
144    return (ImmutableListMultimap<K, V>) EmptyImmutableListMultimap.INSTANCE;
145  }
146
147  /**
148   * Returns an immutable multimap containing a single entry.
149   */
150  public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1) {
151    ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
152    builder.put(k1, v1);
153    return builder.build();
154  }
155
156  /**
157   * Returns an immutable multimap containing the given entries, in order.
158   */
159  public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2) {
160    ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
161    builder.put(k1, v1);
162    builder.put(k2, v2);
163    return builder.build();
164  }
165
166  /**
167   * Returns an immutable multimap containing the given entries, in order.
168   */
169  public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
170    ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
171    builder.put(k1, v1);
172    builder.put(k2, v2);
173    builder.put(k3, v3);
174    return builder.build();
175  }
176
177  /**
178   * Returns an immutable multimap containing the given entries, in order.
179   */
180  public static <K, V> ImmutableListMultimap<K, V> of(
181      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
182    ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
183    builder.put(k1, v1);
184    builder.put(k2, v2);
185    builder.put(k3, v3);
186    builder.put(k4, v4);
187    return builder.build();
188  }
189
190  /**
191   * Returns an immutable multimap containing the given entries, in order.
192   */
193  public static <K, V> ImmutableListMultimap<K, V> of(
194      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
195    ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
196    builder.put(k1, v1);
197    builder.put(k2, v2);
198    builder.put(k3, v3);
199    builder.put(k4, v4);
200    builder.put(k5, v5);
201    return builder.build();
202  }
203
204  // looking for of() with > 5 entries? Use the builder instead.
205
206  /**
207   * Returns a new builder. The generated builder is equivalent to the builder
208   * created by the {@link Builder} constructor.
209   */
210  public static <K, V> Builder<K, V> builder() {
211    return new Builder<K, V>();
212  }
213
214  /**
215   * A builder for creating immutable {@code ListMultimap} instances, especially
216   * {@code public static final} multimaps ("constant multimaps"). Example:
217   * <pre>   {@code
218   *
219   *   static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP =
220   *       new ImmutableListMultimap.Builder<String, Integer>()
221   *           .put("one", 1)
222   *           .putAll("several", 1, 2, 3)
223   *           .putAll("many", 1, 2, 3, 4, 5)
224   *           .build();}</pre>
225   *
226   * <p>Builder instances can be reused; it is safe to call {@link #build} multiple
227   * times to build multiple multimaps in series. Each multimap contains the
228   * key-value mappings in the previously created multimaps.
229   *
230   * @since 2.0
231   */
232  public static final class Builder<K, V> extends ImmutableMultimap.Builder<K, V> {
233    /**
234     * Creates a new builder. The returned builder is equivalent to the builder
235     * generated by {@link ImmutableListMultimap#builder}.
236     */
237    public Builder() {}
238
239    @CanIgnoreReturnValue
240    @Override
241    public Builder<K, V> put(K key, V value) {
242      super.put(key, value);
243      return this;
244    }
245
246    /**
247     * {@inheritDoc}
248     *
249     * @since 11.0
250     */
251    @CanIgnoreReturnValue
252    @Override
253    public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
254      super.put(entry);
255      return this;
256    }
257
258    /**
259     * {@inheritDoc}
260     *
261     * @since 19.0
262     */
263    @CanIgnoreReturnValue
264    @Beta
265    @Override
266    public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) {
267      super.putAll(entries);
268      return this;
269    }
270
271    @CanIgnoreReturnValue
272    @Override
273    public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
274      super.putAll(key, values);
275      return this;
276    }
277
278    @CanIgnoreReturnValue
279    @Override
280    public Builder<K, V> putAll(K key, V... values) {
281      super.putAll(key, values);
282      return this;
283    }
284
285    @CanIgnoreReturnValue
286    @Override
287    public Builder<K, V> putAll(Multimap<? extends K, ? extends V> multimap) {
288      super.putAll(multimap);
289      return this;
290    }
291
292    @CanIgnoreReturnValue
293    @Override
294    Builder<K, V> combine(ImmutableMultimap.Builder<K, V> other) {
295      super.combine(other);
296      return this;
297    }
298
299    /**
300     * {@inheritDoc}
301     *
302     * @since 8.0
303     */
304    @CanIgnoreReturnValue
305    @Override
306    public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) {
307      super.orderKeysBy(keyComparator);
308      return this;
309    }
310
311    /**
312     * {@inheritDoc}
313     *
314     * @since 8.0
315     */
316    @CanIgnoreReturnValue
317    @Override
318    public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
319      super.orderValuesBy(valueComparator);
320      return this;
321    }
322
323    /**
324     * Returns a newly-created immutable list multimap.
325     */
326    @Override
327    public ImmutableListMultimap<K, V> build() {
328      return (ImmutableListMultimap<K, V>) super.build();
329    }
330  }
331
332  /**
333   * Returns an immutable multimap containing the same mappings as {@code
334   * multimap}. The generated multimap's key and value orderings correspond to
335   * the iteration ordering of the {@code multimap.asMap()} view.
336   *
337   * <p>Despite the method name, this method attempts to avoid actually copying
338   * the data when it is safe to do so. The exact circumstances under which a
339   * copy will or will not be performed are undocumented and subject to change.
340   *
341   * @throws NullPointerException if any key or value in {@code multimap} is
342   *         null
343   */
344  public static <K, V> ImmutableListMultimap<K, V> copyOf(
345      Multimap<? extends K, ? extends V> multimap) {
346    if (multimap.isEmpty()) {
347      return of();
348    }
349
350    // TODO(lowasser): copy ImmutableSetMultimap by using asList() on the sets
351    if (multimap instanceof ImmutableListMultimap) {
352      @SuppressWarnings("unchecked") // safe since multimap is not writable
353      ImmutableListMultimap<K, V> kvMultimap = (ImmutableListMultimap<K, V>) multimap;
354      if (!kvMultimap.isPartialView()) {
355        return kvMultimap;
356      }
357    }
358
359    ImmutableMap.Builder<K, ImmutableList<V>> builder =
360        new ImmutableMap.Builder<K, ImmutableList<V>>(multimap.asMap().size());
361    int size = 0;
362
363    for (Entry<? extends K, ? extends Collection<? extends V>> entry :
364        multimap.asMap().entrySet()) {
365      ImmutableList<V> list = ImmutableList.copyOf(entry.getValue());
366      if (!list.isEmpty()) {
367        builder.put(entry.getKey(), list);
368        size += list.size();
369      }
370    }
371
372    return new ImmutableListMultimap<K, V>(builder.build(), size);
373  }
374
375  /**
376   * Returns an immutable multimap containing the specified entries.  The
377   * returned multimap iterates over keys in the order they were first
378   * encountered in the input, and the values for each key are iterated in the
379   * order they were encountered.
380   *
381   * @throws NullPointerException if any key, value, or entry is null
382   * @since 19.0
383   */
384  @Beta
385  public static <K, V> ImmutableListMultimap<K, V> copyOf(
386      Iterable<? extends Entry<? extends K, ? extends V>> entries) {
387    return new Builder<K, V>().putAll(entries).build();
388  }
389
390  ImmutableListMultimap(ImmutableMap<K, ImmutableList<V>> map, int size) {
391    super(map, size);
392  }
393
394  // views
395
396  /**
397   * Returns an immutable list of the values for the given key.  If no mappings
398   * in the multimap have the provided key, an empty immutable list is
399   * returned. The values are in the same order as the parameters used to build
400   * this multimap.
401   */
402  @Override
403  public ImmutableList<V> get(@Nullable K key) {
404    // This cast is safe as its type is known in constructor.
405    ImmutableList<V> list = (ImmutableList<V>) map.get(key);
406    return (list == null) ? ImmutableList.<V>of() : list;
407  }
408
409  @LazyInit
410  @RetainedWith
411  private transient ImmutableListMultimap<V, K> inverse;
412
413  /**
414   * {@inheritDoc}
415   *
416   * <p>Because an inverse of a list multimap can contain multiple pairs with
417   * the same key and value, this method returns an {@code
418   * ImmutableListMultimap} rather than the {@code ImmutableMultimap} specified
419   * in the {@code ImmutableMultimap} class.
420   *
421   * @since 11.0
422   */
423  @Override
424  public ImmutableListMultimap<V, K> inverse() {
425    ImmutableListMultimap<V, K> result = inverse;
426    return (result == null) ? (inverse = invert()) : result;
427  }
428
429  private ImmutableListMultimap<V, K> invert() {
430    Builder<V, K> builder = builder();
431    for (Entry<K, V> entry : entries()) {
432      builder.put(entry.getValue(), entry.getKey());
433    }
434    ImmutableListMultimap<V, K> invertedMultimap = builder.build();
435    invertedMultimap.inverse = this;
436    return invertedMultimap;
437  }
438
439  /**
440   * Guaranteed to throw an exception and leave the multimap unmodified.
441   *
442   * @throws UnsupportedOperationException always
443   * @deprecated Unsupported operation.
444   */
445  @CanIgnoreReturnValue
446  @Deprecated
447  @Override
448  public ImmutableList<V> removeAll(Object key) {
449    throw new UnsupportedOperationException();
450  }
451
452  /**
453   * Guaranteed to throw an exception and leave the multimap unmodified.
454   *
455   * @throws UnsupportedOperationException always
456   * @deprecated Unsupported operation.
457   */
458  @CanIgnoreReturnValue
459  @Deprecated
460  @Override
461  public ImmutableList<V> replaceValues(K key, Iterable<? extends V> values) {
462    throw new UnsupportedOperationException();
463  }
464
465  /**
466   * @serialData number of distinct keys, and then for each distinct key: the
467   *     key, the number of values for that key, and the key's values
468   */
469  @GwtIncompatible // java.io.ObjectOutputStream
470  private void writeObject(ObjectOutputStream stream) throws IOException {
471    stream.defaultWriteObject();
472    Serialization.writeMultimap(this, stream);
473  }
474
475  @GwtIncompatible // java.io.ObjectInputStream
476  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
477    stream.defaultReadObject();
478    int keyCount = stream.readInt();
479    if (keyCount < 0) {
480      throw new InvalidObjectException("Invalid key count " + keyCount);
481    }
482    ImmutableMap.Builder<Object, ImmutableList<Object>> builder = ImmutableMap.builder();
483    int tmpSize = 0;
484
485    for (int i = 0; i < keyCount; i++) {
486      Object key = stream.readObject();
487      int valueCount = stream.readInt();
488      if (valueCount <= 0) {
489        throw new InvalidObjectException("Invalid value count " + valueCount);
490      }
491
492      ImmutableList.Builder<Object> valuesBuilder = ImmutableList.builder();
493      for (int j = 0; j < valueCount; j++) {
494        valuesBuilder.add(stream.readObject());
495      }
496      builder.put(key, valuesBuilder.build());
497      tmpSize += valueCount;
498    }
499
500    ImmutableMap<Object, ImmutableList<Object>> tmpMap;
501    try {
502      tmpMap = builder.build();
503    } catch (IllegalArgumentException e) {
504      throw (InvalidObjectException) new InvalidObjectException(e.getMessage()).initCause(e);
505    }
506
507    FieldSettersHolder.MAP_FIELD_SETTER.set(this, tmpMap);
508    FieldSettersHolder.SIZE_FIELD_SETTER.set(this, tmpSize);
509  }
510
511  @GwtIncompatible // Not needed in emulated source
512  private static final long serialVersionUID = 0;
513}