1 /*
2 * Copyright (C) 2008 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package com.google.common.collect;
18
19
20 import com.google.common.annotations.Beta;
21 import com.google.common.annotations.GwtCompatible;
22 import com.google.common.annotations.GwtIncompatible;
23 import com.google.errorprone.annotations.CanIgnoreReturnValue;
24 import com.google.errorprone.annotations.DoNotCall;
25 import com.google.errorprone.annotations.concurrent.LazyInit;
26 import com.google.j2objc.annotations.RetainedWith;
27 import java.io.IOException;
28 import java.io.InvalidObjectException;
29 import java.io.ObjectInputStream;
30 import java.io.ObjectOutputStream;
31 import java.util.Collection;
32 import java.util.Comparator;
33 import java.util.Map;
34 import java.util.Map.Entry;
35 import java.util.function.Function;
36 import java.util.stream.Collector;
37 import java.util.stream.Stream;
38 import org.checkerframework.checker.nullness.qual.Nullable;
39
40 /**
41 * A {@link ListMultimap} whose contents will never change, with many other important properties
42 * detailed at {@link ImmutableCollection}.
43 *
44 * <p>See the Guava User Guide article on <a href=
45 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained"> immutable collections</a>.
46 *
47 * @author Jared Levy
48 * @since 2.0
49 */
50 @GwtCompatible(serializable = true, emulated = true)
51 public class ImmutableListMultimap<K, V> extends ImmutableMultimap<K, V>
52 implements ListMultimap<K, V> {
53 /**
54 * Returns a {@link Collector} that accumulates elements into an {@code ImmutableListMultimap}
55 * whose keys and values are the result of applying the provided mapping functions to the input
56 * elements.
57 *
58 * <p>For streams with defined encounter order (as defined in the Ordering section of the {@link
59 * java.util.stream} Javadoc), that order is preserved, but entries are <a
60 * href="ImmutableMultimap.html#iteration">grouped by key</a>.
61 *
62 * <p>Example:
63 *
64 * <pre>{@code
65 * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
66 * Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
67 * .collect(toImmutableListMultimap(str -> str.charAt(0), str -> str.substring(1)));
68 *
69 * // is equivalent to
70 *
71 * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
72 * new ImmutableListMultimap.Builder<Character, String>()
73 * .put('b', "anana")
74 * .putAll('a', "pple", "sparagus")
75 * .putAll('c', "arrot", "herry")
76 * .build();
77 * }</pre>
78 *
79 * @since 21.0
80 */
81 public static <T, K, V> Collector<T, ?, ImmutableListMultimap<K, V>> toImmutableListMultimap(
82 Function<? super T, ? extends K> keyFunction,
83 Function<? super T, ? extends V> valueFunction) {
84 return CollectCollectors.toImmutableListMultimap(keyFunction, valueFunction);
85 }
86
87 /**
88 * Returns a {@code Collector} accumulating entries into an {@code ImmutableListMultimap}. Each
89 * input element is mapped to a key and a stream of values, each of which are put into the
90 * resulting {@code Multimap}, in the encounter order of the stream and the encounter order of the
91 * streams of values.
92 *
93 * <p>Example:
94 *
95 * <pre>{@code
96 * static final ImmutableListMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
97 * Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
98 * .collect(
99 * flatteningToImmutableListMultimap(
100 * str -> str.charAt(0),
101 * str -> str.substring(1).chars().mapToObj(c -> (char) c));
102 *
103 * // is equivalent to
104 *
105 * static final ImmutableListMultimap<Character, Character> FIRST_LETTER_MULTIMAP =
106 * ImmutableListMultimap.<Character, Character>builder()
107 * .putAll('b', Arrays.asList('a', 'n', 'a', 'n', 'a'))
108 * .putAll('a', Arrays.asList('p', 'p', 'l', 'e'))
109 * .putAll('c', Arrays.asList('a', 'r', 'r', 'o', 't'))
110 * .putAll('a', Arrays.asList('s', 'p', 'a', 'r', 'a', 'g', 'u', 's'))
111 * .putAll('c', Arrays.asList('h', 'e', 'r', 'r', 'y'))
112 * .build();
113 * }
114 * }</pre>
115 *
116 * @since 21.0
117 */
118 public static <T, K, V>
119 Collector<T, ?, ImmutableListMultimap<K, V>> flatteningToImmutableListMultimap(
120 Function<? super T, ? extends K> keyFunction,
121 Function<? super T, ? extends Stream<? extends V>> valuesFunction) {
122 return CollectCollectors.flatteningToImmutableListMultimap(keyFunction, valuesFunction);
123 }
124
125 /**
126 * Returns the empty multimap.
127 *
128 * <p><b>Performance note:</b> the instance returned is a singleton.
129 */
130 // Casting is safe because the multimap will never hold any elements.
131 @SuppressWarnings("unchecked")
132 public static <K, V> ImmutableListMultimap<K, V> of() {
133 return (ImmutableListMultimap<K, V>) EmptyImmutableListMultimap.INSTANCE;
134 }
135
136 /** Returns an immutable multimap containing a single entry. */
137 public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1) {
138 ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
139 builder.put(k1, v1);
140 return builder.build();
141 }
142
143 /** Returns an immutable multimap containing the given entries, in order. */
144 public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2) {
145 ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
146 builder.put(k1, v1);
147 builder.put(k2, v2);
148 return builder.build();
149 }
150
151 /** Returns an immutable multimap containing the given entries, in order. */
152 public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
153 ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
154 builder.put(k1, v1);
155 builder.put(k2, v2);
156 builder.put(k3, v3);
157 return builder.build();
158 }
159
160 /** Returns an immutable multimap containing the given entries, in order. */
161 public static <K, V> ImmutableListMultimap<K, V> of(
162 K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
163 ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
164 builder.put(k1, v1);
165 builder.put(k2, v2);
166 builder.put(k3, v3);
167 builder.put(k4, v4);
168 return builder.build();
169 }
170
171 /** Returns an immutable multimap containing the given entries, in order. */
172 public static <K, V> ImmutableListMultimap<K, V> of(
173 K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
174 ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
175 builder.put(k1, v1);
176 builder.put(k2, v2);
177 builder.put(k3, v3);
178 builder.put(k4, v4);
179 builder.put(k5, v5);
180 return builder.build();
181 }
182
183 // looking for of() with > 5 entries? Use the builder instead.
184
185 /**
186 * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
187 * Builder} constructor.
188 */
189 public static <K, V> Builder<K, V> builder() {
190 return new Builder<>();
191 }
192
193 /**
194 * A builder for creating immutable {@code ListMultimap} instances, especially {@code public
195 * static final} multimaps ("constant multimaps"). Example:
196 *
197 * <pre>{@code
198 * static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP =
199 * new ImmutableListMultimap.Builder<String, Integer>()
200 * .put("one", 1)
201 * .putAll("several", 1, 2, 3)
202 * .putAll("many", 1, 2, 3, 4, 5)
203 * .build();
204 * }</pre>
205 *
206 * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build
207 * multiple multimaps in series. Each multimap contains the key-value mappings in the previously
208 * created multimaps.
209 *
210 * @since 2.0
211 */
212 public static final class Builder<K, V> extends ImmutableMultimap.Builder<K, V> {
213 /**
214 * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
215 * ImmutableListMultimap#builder}.
216 */
217 public Builder() {}
218
219 @CanIgnoreReturnValue
220 @Override
221 public Builder<K, V> put(K key, V value) {
222 super.put(key, value);
223 return this;
224 }
225
226 /**
227 * {@inheritDoc}
228 *
229 * @since 11.0
230 */
231 @CanIgnoreReturnValue
232 @Override
233 public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
234 super.put(entry);
235 return this;
236 }
237
238 /**
239 * {@inheritDoc}
240 *
241 * @since 19.0
242 */
243 @CanIgnoreReturnValue
244 @Beta
245 @Override
246 public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) {
247 super.putAll(entries);
248 return this;
249 }
250
251 @CanIgnoreReturnValue
252 @Override
253 public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
254 super.putAll(key, values);
255 return this;
256 }
257
258 @CanIgnoreReturnValue
259 @Override
260 public Builder<K, V> putAll(K key, V... values) {
261 super.putAll(key, values);
262 return this;
263 }
264
265 @CanIgnoreReturnValue
266 @Override
267 public Builder<K, V> putAll(Multimap<? extends K, ? extends V> multimap) {
268 super.putAll(multimap);
269 return this;
270 }
271
272 @CanIgnoreReturnValue
273 @Override
274 Builder<K, V> combine(ImmutableMultimap.Builder<K, V> other) {
275 super.combine(other);
276 return this;
277 }
278
279 /**
280 * {@inheritDoc}
281 *
282 * @since 8.0
283 */
284 @CanIgnoreReturnValue
285 @Override
286 public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) {
287 super.orderKeysBy(keyComparator);
288 return this;
289 }
290
291 /**
292 * {@inheritDoc}
293 *
294 * @since 8.0
295 */
296 @CanIgnoreReturnValue
297 @Override
298 public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
299 super.orderValuesBy(valueComparator);
300 return this;
301 }
302
303 /** Returns a newly-created immutable list multimap. */
304 @Override
305 public ImmutableListMultimap<K, V> build() {
306 return (ImmutableListMultimap<K, V>) super.build();
307 }
308 }
309
310 /**
311 * Returns an immutable multimap containing the same mappings as {@code multimap}. The generated
312 * multimap's key and value orderings correspond to the iteration ordering of the {@code
313 * multimap.asMap()} view.
314 *
315 * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
316 * safe to do so. The exact circumstances under which a copy will or will not be performed are
317 * undocumented and subject to change.
318 *
319 * @throws NullPointerException if any key or value in {@code multimap} is null
320 */
321 public static <K, V> ImmutableListMultimap<K, V> copyOf(
322 Multimap<? extends K, ? extends V> multimap) {
323 if (multimap.isEmpty()) {
324 return of();
325 }
326
327 // TODO(lowasser): copy ImmutableSetMultimap by using asList() on the sets
328 if (multimap instanceof ImmutableListMultimap) {
329 @SuppressWarnings("unchecked") // safe since multimap is not writable
330 ImmutableListMultimap<K, V> kvMultimap = (ImmutableListMultimap<K, V>) multimap;
331 if (!kvMultimap.isPartialView()) {
332 return kvMultimap;
333 }
334 }
335
336 return fromMapEntries(multimap.asMap().entrySet(), null);
337 }
338
339 /**
340 * Returns an immutable multimap containing the specified entries. The returned multimap iterates
341 * over keys in the order they were first encountered in the input, and the values for each key
342 * are iterated in the order they were encountered.
343 *
344 * @throws NullPointerException if any key, value, or entry is null
345 * @since 19.0
346 */
347 @Beta
348 public static <K, V> ImmutableListMultimap<K, V> copyOf(
349 Iterable<? extends Entry<? extends K, ? extends V>> entries) {
350 return new Builder<K, V>().putAll(entries).build();
351 }
352
353 /** Creates an ImmutableListMultimap from an asMap.entrySet. */
354 static <K, V> ImmutableListMultimap<K, V> fromMapEntries(
355 Collection<? extends Map.Entry<? extends K, ? extends Collection<? extends V>>> mapEntries,
356 @Nullable Comparator<? super V> valueComparator) {
357 if (mapEntries.isEmpty()) {
358 return of();
359 }
360 ImmutableMap.Builder<K, ImmutableList<V>> builder =
361 new ImmutableMap.Builder<>(mapEntries.size());
362 int size = 0;
363
364 for (Entry<? extends K, ? extends Collection<? extends V>> entry : mapEntries) {
365 K key = entry.getKey();
366 Collection<? extends V> values = entry.getValue();
367 ImmutableList<V> list =
368 (valueComparator == null)
369 ? ImmutableList.copyOf(values)
370 : ImmutableList.sortedCopyOf(valueComparator, values);
371 if (!list.isEmpty()) {
372 builder.put(key, list);
373 size += list.size();
374 }
375 }
376
377 return new ImmutableListMultimap<>(builder.build(), size);
378 }
379
380 ImmutableListMultimap(ImmutableMap<K, ImmutableList<V>> map, int size) {
381 super(map, size);
382 }
383
384 // views
385
386 /**
387 * Returns an immutable list of the values for the given key. If no mappings in the multimap have
388 * the provided key, an empty immutable list is returned. The values are in the same order as the
389 * parameters used to build this multimap.
390 */
391 @Override
392 public ImmutableList<V> get(@Nullable K key) {
393 // This cast is safe as its type is known in constructor.
394 ImmutableList<V> list = (ImmutableList<V>) map.get(key);
395 return (list == null) ? ImmutableList.<V>of() : list;
396 }
397
398 @LazyInit @RetainedWith private transient ImmutableListMultimap<V, K> inverse;
399
400 /**
401 * {@inheritDoc}
402 *
403 * <p>Because an inverse of a list multimap can contain multiple pairs with the same key and
404 * value, this method returns an {@code ImmutableListMultimap} rather than the {@code
405 * ImmutableMultimap} specified in the {@code ImmutableMultimap} class.
406 *
407 * @since 11.0
408 */
409 @Override
410 public ImmutableListMultimap<V, K> inverse() {
411 ImmutableListMultimap<V, K> result = inverse;
412 return (result == null) ? (inverse = invert()) : result;
413 }
414
415 private ImmutableListMultimap<V, K> invert() {
416 Builder<V, K> builder = builder();
417 for (Entry<K, V> entry : entries()) {
418 builder.put(entry.getValue(), entry.getKey());
419 }
420 ImmutableListMultimap<V, K> invertedMultimap = builder.build();
421 invertedMultimap.inverse = this;
422 return invertedMultimap;
423 }
424
425 /**
426 * Guaranteed to throw an exception and leave the multimap unmodified.
427 *
428 * @throws UnsupportedOperationException always
429 * @deprecated Unsupported operation.
430 */
431 @CanIgnoreReturnValue
432 @Deprecated
433 @Override
434 @DoNotCall("Always throws UnsupportedOperationException")
435 public final ImmutableList<V> removeAll(Object key) {
436 throw new UnsupportedOperationException();
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 @DoNotCall("Always throws UnsupportedOperationException")
449 public final ImmutableList<V> replaceValues(K key, Iterable<? extends V> values) {
450 throw new UnsupportedOperationException();
451 }
452
453 /**
454 * @serialData number of distinct keys, and then for each distinct key: the key, the number of
455 * values for that key, and the key's values
456 */
457 @GwtIncompatible // java.io.ObjectOutputStream
458 private void writeObject(ObjectOutputStream stream) throws IOException {
459 stream.defaultWriteObject();
460 Serialization.writeMultimap(this, stream);
461 }
462
463 @GwtIncompatible // java.io.ObjectInputStream
464 private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
465 stream.defaultReadObject();
466 int keyCount = stream.readInt();
467 if (keyCount < 0) {
468 throw new InvalidObjectException("Invalid key count " + keyCount);
469 }
470 ImmutableMap.Builder<Object, ImmutableList<Object>> builder = ImmutableMap.builder();
471 int tmpSize = 0;
472
473 for (int i = 0; i < keyCount; i++) {
474 Object key = stream.readObject();
475 int valueCount = stream.readInt();
476 if (valueCount <= 0) {
477 throw new InvalidObjectException("Invalid value count " + valueCount);
478 }
479
480 ImmutableList.Builder<Object> valuesBuilder = ImmutableList.builder();
481 for (int j = 0; j < valueCount; j++) {
482 valuesBuilder.add(stream.readObject());
483 }
484 builder.put(key, valuesBuilder.build());
485 tmpSize += valueCount;
486 }
487
488 ImmutableMap<Object, ImmutableList<Object>> tmpMap;
489 try {
490 tmpMap = builder.build();
491 } catch (IllegalArgumentException e) {
492 throw (InvalidObjectException) new InvalidObjectException(e.getMessage()).initCause(e);
493 }
494
495 FieldSettersHolder.MAP_FIELD_SETTER.set(this, tmpMap);
496 FieldSettersHolder.SIZE_FIELD_SETTER.set(this, tmpSize);
497 }
498
499 @GwtIncompatible // Not needed in emulated source
500 private static final long serialVersionUID = 0;
501 }