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 java.util.Objects.requireNonNull;
020
021import com.google.common.annotations.GwtCompatible;
022import com.google.common.annotations.GwtIncompatible;
023import com.google.common.annotations.J2ktIncompatible;
024import com.google.errorprone.annotations.CanIgnoreReturnValue;
025import com.google.errorprone.annotations.DoNotCall;
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.Stream;
039import javax.annotation.CheckForNull;
040import org.checkerframework.checker.nullness.qual.Nullable;
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)
053@ElementTypesAreNonnullByDefault
054public class ImmutableListMultimap<K, V> extends ImmutableMultimap<K, V>
055    implements ListMultimap<K, V> {
056  /**
057   * Returns a {@link Collector} that accumulates elements into an {@code ImmutableListMultimap}
058   * whose keys and values are the result of applying the provided mapping functions to the input
059   * elements.
060   *
061   * <p>For streams with defined encounter order (as defined in the Ordering section of the {@link
062   * java.util.stream} Javadoc), that order is preserved, but entries are <a
063   * href="ImmutableMultimap.html#iteration">grouped by key</a>.
064   *
065   * <p>Example:
066   *
067   * <pre>{@code
068   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
069   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
070   *         .collect(toImmutableListMultimap(str -> str.charAt(0), str -> str.substring(1)));
071   *
072   * // is equivalent to
073   *
074   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
075   *     new ImmutableListMultimap.Builder<Character, String>()
076   *         .put('b', "anana")
077   *         .putAll('a', "pple", "sparagus")
078   *         .putAll('c', "arrot", "herry")
079   *         .build();
080   * }</pre>
081   *
082   * @since 21.0
083   */
084  public static <T extends @Nullable Object, K, V>
085      Collector<T, ?, ImmutableListMultimap<K, V>> toImmutableListMultimap(
086          Function<? super T, ? extends K> keyFunction,
087          Function<? super T, ? extends V> valueFunction) {
088    return CollectCollectors.toImmutableListMultimap(keyFunction, valueFunction);
089  }
090
091  /**
092   * Returns a {@code Collector} accumulating entries into an {@code ImmutableListMultimap}. Each
093   * input element is mapped to a key and a stream of values, each of which are put into the
094   * resulting {@code Multimap}, in the encounter order of the stream and the encounter order of the
095   * streams of values.
096   *
097   * <p>Example:
098   *
099   * <pre>{@code
100   * static final ImmutableListMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
101   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
102   *         .collect(
103   *             flatteningToImmutableListMultimap(
104   *                  str -> str.charAt(0),
105   *                  str -> str.substring(1).chars().mapToObj(c -> (char) c));
106   *
107   * // is equivalent to
108   *
109   * static final ImmutableListMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
110   *     ImmutableListMultimap.<Character, Character>builder()
111   *         .putAll('b', Arrays.asList('a', 'n', 'a', 'n', 'a'))
112   *         .putAll('a', Arrays.asList('p', 'p', 'l', 'e'))
113   *         .putAll('c', Arrays.asList('a', 'r', 'r', 'o', 't'))
114   *         .putAll('a', Arrays.asList('s', 'p', 'a', 'r', 'a', 'g', 'u', 's'))
115   *         .putAll('c', Arrays.asList('h', 'e', 'r', 'r', 'y'))
116   *         .build();
117   * }
118   * }</pre>
119   *
120   * @since 21.0
121   */
122  public static <T extends @Nullable Object, K, V>
123      Collector<T, ?, ImmutableListMultimap<K, V>> flatteningToImmutableListMultimap(
124          Function<? super T, ? extends K> keyFunction,
125          Function<? super T, ? extends Stream<? extends V>> valuesFunction) {
126    return CollectCollectors.flatteningToImmutableListMultimap(keyFunction, valuesFunction);
127  }
128
129  /**
130   * Returns the empty multimap.
131   *
132   * <p><b>Performance note:</b> the instance returned is a singleton.
133   */
134  // Casting is safe because the multimap will never hold any elements.
135  @SuppressWarnings("unchecked")
136  public static <K, V> ImmutableListMultimap<K, V> of() {
137    return (ImmutableListMultimap<K, V>) EmptyImmutableListMultimap.INSTANCE;
138  }
139
140  /** Returns an immutable multimap containing a single entry. */
141  public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1) {
142    ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
143    builder.put(k1, v1);
144    return builder.build();
145  }
146
147  /** Returns an immutable multimap containing the given entries, in order. */
148  public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2) {
149    ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
150    builder.put(k1, v1);
151    builder.put(k2, v2);
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, K k3, V v3) {
157    ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
158    builder.put(k1, v1);
159    builder.put(k2, v2);
160    builder.put(k3, v3);
161    return builder.build();
162  }
163
164  /** Returns an immutable multimap containing the given entries, in order. */
165  public static <K, V> ImmutableListMultimap<K, V> of(
166      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
167    ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
168    builder.put(k1, v1);
169    builder.put(k2, v2);
170    builder.put(k3, v3);
171    builder.put(k4, v4);
172    return builder.build();
173  }
174
175  /** Returns an immutable multimap containing the given entries, in order. */
176  public static <K, V> ImmutableListMultimap<K, V> of(
177      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
178    ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
179    builder.put(k1, v1);
180    builder.put(k2, v2);
181    builder.put(k3, v3);
182    builder.put(k4, v4);
183    builder.put(k5, v5);
184    return builder.build();
185  }
186
187  // looking for of() with > 5 entries? Use the builder instead.
188
189  /**
190   * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
191   * Builder} constructor.
192   */
193  public static <K, V> Builder<K, V> builder() {
194    return new Builder<>();
195  }
196
197  /**
198   * A builder for creating immutable {@code ListMultimap} instances, especially {@code public
199   * static final} multimaps ("constant multimaps"). Example:
200   *
201   * <pre>{@code
202   * static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP =
203   *     new ImmutableListMultimap.Builder<String, Integer>()
204   *         .put("one", 1)
205   *         .putAll("several", 1, 2, 3)
206   *         .putAll("many", 1, 2, 3, 4, 5)
207   *         .build();
208   * }</pre>
209   *
210   * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build
211   * multiple multimaps in series. Each multimap contains the key-value mappings in the previously
212   * created multimaps.
213   *
214   * @since 2.0
215   */
216  public static final class Builder<K, V> extends ImmutableMultimap.Builder<K, V> {
217    /**
218     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
219     * ImmutableListMultimap#builder}.
220     */
221    public Builder() {}
222
223    @CanIgnoreReturnValue
224    @Override
225    public Builder<K, V> put(K key, V value) {
226      super.put(key, value);
227      return this;
228    }
229
230    /**
231     * {@inheritDoc}
232     *
233     * @since 11.0
234     */
235    @CanIgnoreReturnValue
236    @Override
237    public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
238      super.put(entry);
239      return this;
240    }
241
242    /**
243     * {@inheritDoc}
244     *
245     * @since 19.0
246     */
247    @CanIgnoreReturnValue
248    @Override
249    public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) {
250      super.putAll(entries);
251      return this;
252    }
253
254    @CanIgnoreReturnValue
255    @Override
256    public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
257      super.putAll(key, values);
258      return this;
259    }
260
261    @CanIgnoreReturnValue
262    @Override
263    public Builder<K, V> putAll(K key, V... values) {
264      super.putAll(key, values);
265      return this;
266    }
267
268    @CanIgnoreReturnValue
269    @Override
270    public Builder<K, V> putAll(Multimap<? extends K, ? extends V> multimap) {
271      super.putAll(multimap);
272      return this;
273    }
274
275    @CanIgnoreReturnValue
276    @Override
277    Builder<K, V> combine(ImmutableMultimap.Builder<K, V> other) {
278      super.combine(other);
279      return this;
280    }
281
282    /**
283     * {@inheritDoc}
284     *
285     * @since 8.0
286     */
287    @CanIgnoreReturnValue
288    @Override
289    public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) {
290      super.orderKeysBy(keyComparator);
291      return this;
292    }
293
294    /**
295     * {@inheritDoc}
296     *
297     * @since 8.0
298     */
299    @CanIgnoreReturnValue
300    @Override
301    public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
302      super.orderValuesBy(valueComparator);
303      return this;
304    }
305
306    /** Returns a newly-created immutable list multimap. */
307    @Override
308    public ImmutableListMultimap<K, V> build() {
309      return (ImmutableListMultimap<K, V>) super.build();
310    }
311  }
312
313  /**
314   * Returns an immutable multimap containing the same mappings as {@code multimap}. The generated
315   * multimap's key and value orderings correspond to the iteration ordering of the {@code
316   * multimap.asMap()} view.
317   *
318   * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
319   * safe to do so. The exact circumstances under which a copy will or will not be performed are
320   * undocumented and subject to change.
321   *
322   * @throws NullPointerException if any key or value in {@code multimap} is null
323   */
324  public static <K, V> ImmutableListMultimap<K, V> copyOf(
325      Multimap<? extends K, ? extends V> multimap) {
326    if (multimap.isEmpty()) {
327      return of();
328    }
329
330    // TODO(lowasser): copy ImmutableSetMultimap by using asList() on the sets
331    if (multimap instanceof ImmutableListMultimap) {
332      @SuppressWarnings("unchecked") // safe since multimap is not writable
333      ImmutableListMultimap<K, V> kvMultimap = (ImmutableListMultimap<K, V>) multimap;
334      if (!kvMultimap.isPartialView()) {
335        return kvMultimap;
336      }
337    }
338
339    return fromMapEntries(multimap.asMap().entrySet(), null);
340  }
341
342  /**
343   * Returns an immutable multimap containing the specified entries. The returned multimap iterates
344   * over keys in the order they were first encountered in the input, and the values for each key
345   * are iterated in the order they were encountered.
346   *
347   * @throws NullPointerException if any key, value, or entry is null
348   * @since 19.0
349   */
350  public static <K, V> ImmutableListMultimap<K, V> copyOf(
351      Iterable<? extends Entry<? extends K, ? extends V>> entries) {
352    return new Builder<K, V>().putAll(entries).build();
353  }
354
355  /** Creates an ImmutableListMultimap from an asMap.entrySet. */
356  static <K, V> ImmutableListMultimap<K, V> fromMapEntries(
357      Collection<? extends Map.Entry<? extends K, ? extends Collection<? extends V>>> mapEntries,
358      @CheckForNull Comparator<? super V> valueComparator) {
359    if (mapEntries.isEmpty()) {
360      return of();
361    }
362    ImmutableMap.Builder<K, ImmutableList<V>> builder =
363        new ImmutableMap.Builder<>(mapEntries.size());
364    int size = 0;
365
366    for (Entry<? extends K, ? extends Collection<? extends V>> entry : mapEntries) {
367      K key = entry.getKey();
368      Collection<? extends V> values = entry.getValue();
369      ImmutableList<V> list =
370          (valueComparator == null)
371              ? ImmutableList.copyOf(values)
372              : ImmutableList.sortedCopyOf(valueComparator, values);
373      if (!list.isEmpty()) {
374        builder.put(key, list);
375        size += list.size();
376      }
377    }
378
379    return new ImmutableListMultimap<>(builder.buildOrThrow(), size);
380  }
381
382  ImmutableListMultimap(ImmutableMap<K, ImmutableList<V>> map, int size) {
383    super(map, size);
384  }
385
386  // views
387
388  /**
389   * Returns an immutable list of the values for the given key. If no mappings in the multimap have
390   * the provided key, an empty immutable list is returned. The values are in the same order as the
391   * parameters used to build this multimap.
392   */
393  @Override
394  public ImmutableList<V> get(K key) {
395    // This cast is safe as its type is known in constructor.
396    ImmutableList<V> list = (ImmutableList<V>) map.get(key);
397    return (list == null) ? ImmutableList.<V>of() : list;
398  }
399
400  @LazyInit @RetainedWith @CheckForNull private transient ImmutableListMultimap<V, K> inverse;
401
402  /**
403   * {@inheritDoc}
404   *
405   * <p>Because an inverse of a list multimap can contain multiple pairs with the same key and
406   * value, this method returns an {@code ImmutableListMultimap} rather than the {@code
407   * ImmutableMultimap} specified in the {@code ImmutableMultimap} class.
408   *
409   * @since 11.0
410   */
411  @Override
412  public ImmutableListMultimap<V, K> inverse() {
413    ImmutableListMultimap<V, K> result = inverse;
414    return (result == null) ? (inverse = invert()) : result;
415  }
416
417  private ImmutableListMultimap<V, K> invert() {
418    Builder<V, K> builder = builder();
419    for (Entry<K, V> entry : entries()) {
420      builder.put(entry.getValue(), entry.getKey());
421    }
422    ImmutableListMultimap<V, K> invertedMultimap = builder.build();
423    invertedMultimap.inverse = this;
424    return invertedMultimap;
425  }
426
427  /**
428   * Guaranteed to throw an exception and leave the multimap unmodified.
429   *
430   * @throws UnsupportedOperationException always
431   * @deprecated Unsupported operation.
432   */
433  @CanIgnoreReturnValue
434  @Deprecated
435  @Override
436  @DoNotCall("Always throws UnsupportedOperationException")
437  public final ImmutableList<V> removeAll(@CheckForNull Object key) {
438    throw new UnsupportedOperationException();
439  }
440
441  /**
442   * Guaranteed to throw an exception and leave the multimap unmodified.
443   *
444   * @throws UnsupportedOperationException always
445   * @deprecated Unsupported operation.
446   */
447  @CanIgnoreReturnValue
448  @Deprecated
449  @Override
450  @DoNotCall("Always throws UnsupportedOperationException")
451  public final ImmutableList<V> replaceValues(K key, Iterable<? extends V> values) {
452    throw new UnsupportedOperationException();
453  }
454
455  /**
456   * @serialData number of distinct keys, and then for each distinct key: the key, the number of
457   *     values for that key, and the key's values
458   */
459  @GwtIncompatible // java.io.ObjectOutputStream
460  @J2ktIncompatible
461  private void writeObject(ObjectOutputStream stream) throws IOException {
462    stream.defaultWriteObject();
463    Serialization.writeMultimap(this, stream);
464  }
465
466  @GwtIncompatible // java.io.ObjectInputStream
467  @J2ktIncompatible
468  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
469    stream.defaultReadObject();
470    int keyCount = stream.readInt();
471    if (keyCount < 0) {
472      throw new InvalidObjectException("Invalid key count " + keyCount);
473    }
474    ImmutableMap.Builder<Object, ImmutableList<Object>> builder = ImmutableMap.builder();
475    int tmpSize = 0;
476
477    for (int i = 0; i < keyCount; i++) {
478      Object key = requireNonNull(stream.readObject());
479      int valueCount = stream.readInt();
480      if (valueCount <= 0) {
481        throw new InvalidObjectException("Invalid value count " + valueCount);
482      }
483
484      ImmutableList.Builder<Object> valuesBuilder = ImmutableList.builder();
485      for (int j = 0; j < valueCount; j++) {
486        valuesBuilder.add(requireNonNull(stream.readObject()));
487      }
488      builder.put(key, valuesBuilder.build());
489      tmpSize += valueCount;
490    }
491
492    ImmutableMap<Object, ImmutableList<Object>> tmpMap;
493    try {
494      tmpMap = builder.buildOrThrow();
495    } catch (IllegalArgumentException e) {
496      throw (InvalidObjectException) new InvalidObjectException(e.getMessage()).initCause(e);
497    }
498
499    FieldSettersHolder.MAP_FIELD_SETTER.set(this, tmpMap);
500    FieldSettersHolder.SIZE_FIELD_SETTER.set(this, tmpSize);
501  }
502
503  @GwtIncompatible // Not needed in emulated source
504  @J2ktIncompatible
505  private static final long serialVersionUID = 0;
506}