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