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