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}