1/* 2 * Copyright (C) 2009 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 17package com.google.common.collect; 18 19import static com.google.common.base.Preconditions.checkNotNull; 20 21import com.google.common.annotations.GwtCompatible; 22import com.google.common.base.MoreObjects; 23 24import java.util.Arrays; 25import java.util.Collection; 26import java.util.Collections; 27import java.util.Comparator; 28import java.util.LinkedHashMap; 29import java.util.List; 30import java.util.Map; 31import java.util.Map.Entry; 32 33import javax.annotation.Nullable; 34 35/** 36 * An immutable {@link SetMultimap} with reliable user-specified key and value 37 * iteration order. Does not permit null keys or values. 38 * 39 * <p>Unlike {@link Multimaps#unmodifiableSetMultimap(SetMultimap)}, which is 40 * a <i>view</i> of a separate multimap which can still change, an instance of 41 * {@code ImmutableSetMultimap} contains its own data and will <i>never</i> 42 * change. {@code ImmutableSetMultimap} is convenient for 43 * {@code public static final} multimaps ("constant multimaps") and also lets 44 * you easily make a "defensive copy" of a multimap provided to your class by 45 * a caller. 46 * 47 * <p><b>Note:</b> Although this class is not final, it cannot be subclassed as 48 * it has no public or protected constructors. Thus, instances of this class 49 * are guaranteed to be immutable. 50 * 51 * <p>See the Guava User Guide article on <a href= 52 * "http://code.google.com/p/guava-libraries/wiki/ImmutableCollectionsExplained"> 53 * immutable collections</a>. 54 * 55 * @author Mike Ward 56 * @since 2.0 (imported from Google Collections Library) 57 */ 58@GwtCompatible(serializable = true, emulated = true) 59public class ImmutableSetMultimap<K, V> 60 extends ImmutableMultimap<K, V> 61 implements SetMultimap<K, V> { 62 63 /** Returns the empty multimap. */ 64 // Casting is safe because the multimap will never hold any elements. 65 @SuppressWarnings("unchecked") 66 public static <K, V> ImmutableSetMultimap<K, V> of() { 67 return (ImmutableSetMultimap<K, V>) EmptyImmutableSetMultimap.INSTANCE; 68 } 69 70 /** 71 * Returns an immutable multimap containing a single entry. 72 */ 73 public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1) { 74 ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder(); 75 builder.put(k1, v1); 76 return builder.build(); 77 } 78 79 /** 80 * Returns an immutable multimap containing the given entries, in order. 81 * Repeated occurrences of an entry (according to {@link Object#equals}) after 82 * the first are ignored. 83 */ 84 public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2) { 85 ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder(); 86 builder.put(k1, v1); 87 builder.put(k2, v2); 88 return builder.build(); 89 } 90 91 /** 92 * Returns an immutable multimap containing the given entries, in order. 93 * Repeated occurrences of an entry (according to {@link Object#equals}) after 94 * the first are ignored. 95 */ 96 public static <K, V> ImmutableSetMultimap<K, V> of( 97 K k1, V v1, K k2, V v2, K k3, V v3) { 98 ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder(); 99 builder.put(k1, v1); 100 builder.put(k2, v2); 101 builder.put(k3, v3); 102 return builder.build(); 103 } 104 105 /** 106 * Returns an immutable multimap containing the given entries, in order. 107 * Repeated occurrences of an entry (according to {@link Object#equals}) after 108 * the first are ignored. 109 */ 110 public static <K, V> ImmutableSetMultimap<K, V> of( 111 K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) { 112 ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder(); 113 builder.put(k1, v1); 114 builder.put(k2, v2); 115 builder.put(k3, v3); 116 builder.put(k4, v4); 117 return builder.build(); 118 } 119 120 /** 121 * Returns an immutable multimap containing the given entries, in order. 122 * Repeated occurrences of an entry (according to {@link Object#equals}) after 123 * the first are ignored. 124 */ 125 public static <K, V> ImmutableSetMultimap<K, V> of( 126 K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) { 127 ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder(); 128 builder.put(k1, v1); 129 builder.put(k2, v2); 130 builder.put(k3, v3); 131 builder.put(k4, v4); 132 builder.put(k5, v5); 133 return builder.build(); 134 } 135 136 // looking for of() with > 5 entries? Use the builder instead. 137 138 /** 139 * Returns a new {@link Builder}. 140 */ 141 public static <K, V> Builder<K, V> builder() { 142 return new Builder<K, V>(); 143 } 144 145 /** 146 * Multimap for {@link ImmutableSetMultimap.Builder} that maintains key 147 * and value orderings and performs better than {@link LinkedHashMultimap}. 148 */ 149 private static class BuilderMultimap<K, V> extends AbstractMapBasedMultimap<K, V> { 150 BuilderMultimap() { 151 super(new LinkedHashMap<K, Collection<V>>()); 152 } 153 @Override Collection<V> createCollection() { 154 return Sets.newLinkedHashSet(); 155 } 156 private static final long serialVersionUID = 0; 157 } 158 159 /** 160 * A builder for creating immutable {@code SetMultimap} instances, especially 161 * {@code public static final} multimaps ("constant multimaps"). Example: 162 * <pre> {@code 163 * 164 * static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP = 165 * new ImmutableSetMultimap.Builder<String, Integer>() 166 * .put("one", 1) 167 * .putAll("several", 1, 2, 3) 168 * .putAll("many", 1, 2, 3, 4, 5) 169 * .build();}</pre> 170 * 171 * <p>Builder instances can be reused; it is safe to call {@link #build} multiple 172 * times to build multiple multimaps in series. Each multimap contains the 173 * key-value mappings in the previously created multimaps. 174 * 175 * @since 2.0 (imported from Google Collections Library) 176 */ 177 public static final class Builder<K, V> 178 extends ImmutableMultimap.Builder<K, V> { 179 /** 180 * Creates a new builder. The returned builder is equivalent to the builder 181 * generated by {@link ImmutableSetMultimap#builder}. 182 */ 183 public Builder() { 184 builderMultimap = new BuilderMultimap<K, V>(); 185 } 186 187 /** 188 * Adds a key-value mapping to the built multimap if it is not already 189 * present. 190 */ 191 @Override public Builder<K, V> put(K key, V value) { 192 builderMultimap.put(checkNotNull(key), checkNotNull(value)); 193 return this; 194 } 195 196 /** 197 * Adds an entry to the built multimap if it is not already present. 198 * 199 * @since 11.0 200 */ 201 @Override public Builder<K, V> put(Entry<? extends K, ? extends V> entry) { 202 builderMultimap.put( 203 checkNotNull(entry.getKey()), checkNotNull(entry.getValue())); 204 return this; 205 } 206 207 @Override public Builder<K, V> putAll(K key, Iterable<? extends V> values) { 208 Collection<V> collection = builderMultimap.get(checkNotNull(key)); 209 for (V value : values) { 210 collection.add(checkNotNull(value)); 211 } 212 return this; 213 } 214 215 @Override public Builder<K, V> putAll(K key, V... values) { 216 return putAll(key, Arrays.asList(values)); 217 } 218 219 @Override public Builder<K, V> putAll( 220 Multimap<? extends K, ? extends V> multimap) { 221 for (Entry<? extends K, ? extends Collection<? extends V>> entry 222 : multimap.asMap().entrySet()) { 223 putAll(entry.getKey(), entry.getValue()); 224 } 225 return this; 226 } 227 228 /** 229 * {@inheritDoc} 230 * 231 * @since 8.0 232 */ 233 @Override 234 public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) { 235 this.keyComparator = checkNotNull(keyComparator); 236 return this; 237 } 238 239 /** 240 * Specifies the ordering of the generated multimap's values for each key. 241 * 242 * <p>If this method is called, the sets returned by the {@code get()} 243 * method of the generated multimap and its {@link Multimap#asMap()} view 244 * are {@link ImmutableSortedSet} instances. However, serialization does not 245 * preserve that property, though it does maintain the key and value 246 * ordering. 247 * 248 * @since 8.0 249 */ 250 // TODO: Make serialization behavior consistent. 251 @Override 252 public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) { 253 super.orderValuesBy(valueComparator); 254 return this; 255 } 256 257 /** 258 * Returns a newly-created immutable set multimap. 259 */ 260 @Override public ImmutableSetMultimap<K, V> build() { 261 if (keyComparator != null) { 262 Multimap<K, V> sortedCopy = new BuilderMultimap<K, V>(); 263 List<Map.Entry<K, Collection<V>>> entries = Lists.newArrayList( 264 builderMultimap.asMap().entrySet()); 265 Collections.sort( 266 entries, 267 Ordering.from(keyComparator).<K>onKeys()); 268 for (Map.Entry<K, Collection<V>> entry : entries) { 269 sortedCopy.putAll(entry.getKey(), entry.getValue()); 270 } 271 builderMultimap = sortedCopy; 272 } 273 return copyOf(builderMultimap, valueComparator); 274 } 275 } 276 277 /** 278 * Returns an immutable set multimap containing the same mappings as 279 * {@code multimap}. The generated multimap's key and value orderings 280 * correspond to the iteration ordering of the {@code multimap.asMap()} view. 281 * Repeated occurrences of an entry in the multimap after the first are 282 * ignored. 283 * 284 * <p>Despite the method name, this method attempts to avoid actually copying 285 * the data when it is safe to do so. The exact circumstances under which a 286 * copy will or will not be performed are undocumented and subject to change. 287 * 288 * @throws NullPointerException if any key or value in {@code multimap} is 289 * null 290 */ 291 public static <K, V> ImmutableSetMultimap<K, V> copyOf( 292 Multimap<? extends K, ? extends V> multimap) { 293 return copyOf(multimap, null); 294 } 295 296 private static <K, V> ImmutableSetMultimap<K, V> copyOf( 297 Multimap<? extends K, ? extends V> multimap, 298 Comparator<? super V> valueComparator) { 299 checkNotNull(multimap); // eager for GWT 300 if (multimap.isEmpty() && valueComparator == null) { 301 return of(); 302 } 303 304 if (multimap instanceof ImmutableSetMultimap) { 305 @SuppressWarnings("unchecked") // safe since multimap is not writable 306 ImmutableSetMultimap<K, V> kvMultimap 307 = (ImmutableSetMultimap<K, V>) multimap; 308 if (!kvMultimap.isPartialView()) { 309 return kvMultimap; 310 } 311 } 312 313 ImmutableMap.Builder<K, ImmutableSet<V>> builder = ImmutableMap.builder(); 314 int size = 0; 315 316 for (Entry<? extends K, ? extends Collection<? extends V>> entry 317 : multimap.asMap().entrySet()) { 318 K key = entry.getKey(); 319 Collection<? extends V> values = entry.getValue(); 320 ImmutableSet<V> set = valueSet(valueComparator, values); 321 if (!set.isEmpty()) { 322 builder.put(key, set); 323 size += set.size(); 324 } 325 } 326 327 return new ImmutableSetMultimap<K, V>( 328 builder.build(), size, valueComparator); 329 } 330 331 /** 332 * Returned by get() when a missing key is provided. Also holds the 333 * comparator, if any, used for values. 334 */ 335 private final transient ImmutableSet<V> emptySet; 336 337 ImmutableSetMultimap(ImmutableMap<K, ImmutableSet<V>> map, int size, 338 @Nullable Comparator<? super V> valueComparator) { 339 super(map, size); 340 this.emptySet = emptySet(valueComparator); 341 } 342 343 // views 344 345 /** 346 * Returns an immutable set of the values for the given key. If no mappings 347 * in the multimap have the provided key, an empty immutable set is returned. 348 * The values are in the same order as the parameters used to build this 349 * multimap. 350 */ 351 @Override public ImmutableSet<V> get(@Nullable K key) { 352 // This cast is safe as its type is known in constructor. 353 ImmutableSet<V> set = (ImmutableSet<V>) map.get(key); 354 return MoreObjects.firstNonNull(set, emptySet); 355 } 356 357 private transient ImmutableSetMultimap<V, K> inverse; 358 359 /** 360 * {@inheritDoc} 361 * 362 * <p>Because an inverse of a set multimap cannot contain multiple pairs with 363 * the same key and value, this method returns an {@code ImmutableSetMultimap} 364 * rather than the {@code ImmutableMultimap} specified in the {@code 365 * ImmutableMultimap} class. 366 * 367 * @since 11.0 368 */ 369 public ImmutableSetMultimap<V, K> inverse() { 370 ImmutableSetMultimap<V, K> result = inverse; 371 return (result == null) ? (inverse = invert()) : result; 372 } 373 374 private ImmutableSetMultimap<V, K> invert() { 375 Builder<V, K> builder = builder(); 376 for (Entry<K, V> entry : entries()) { 377 builder.put(entry.getValue(), entry.getKey()); 378 } 379 ImmutableSetMultimap<V, K> invertedMultimap = builder.build(); 380 invertedMultimap.inverse = this; 381 return invertedMultimap; 382 } 383 384 /** 385 * Guaranteed to throw an exception and leave the multimap unmodified. 386 * 387 * @throws UnsupportedOperationException always 388 * @deprecated Unsupported operation. 389 */ 390 @Deprecated @Override public ImmutableSet<V> removeAll(Object key) { 391 throw new UnsupportedOperationException(); 392 } 393 394 /** 395 * Guaranteed to throw an exception and leave the multimap unmodified. 396 * 397 * @throws UnsupportedOperationException always 398 * @deprecated Unsupported operation. 399 */ 400 @Deprecated @Override public ImmutableSet<V> replaceValues( 401 K key, Iterable<? extends V> values) { 402 throw new UnsupportedOperationException(); 403 } 404 405 private transient ImmutableSet<Entry<K, V>> entries; 406 407 /** 408 * Returns an immutable collection of all key-value pairs in the multimap. 409 * Its iterator traverses the values for the first key, the values for the 410 * second key, and so on. 411 */ 412 @Override public ImmutableSet<Entry<K, V>> entries() { 413 ImmutableSet<Entry<K, V>> result = entries; 414 return (result == null) 415 ? (entries = new EntrySet<K, V>(this)) 416 : result; 417 } 418 419 private static final class EntrySet<K, V> extends ImmutableSet<Entry<K, V>> { 420 private transient final ImmutableSetMultimap<K, V> multimap; 421 422 EntrySet(ImmutableSetMultimap<K, V> multimap) { 423 this.multimap = multimap; 424 } 425 426 @Override 427 public boolean contains(@Nullable Object object) { 428 if (object instanceof Entry) { 429 Entry<?, ?> entry = (Entry<?, ?>) object; 430 return multimap.containsEntry(entry.getKey(), entry.getValue()); 431 } 432 return false; 433 } 434 435 @Override 436 public int size() { 437 return multimap.size(); 438 } 439 440 @Override 441 public UnmodifiableIterator<Entry<K, V>> iterator() { 442 return multimap.entryIterator(); 443 } 444 445 @Override 446 boolean isPartialView() { 447 return false; 448 } 449 } 450 451 private static <V> ImmutableSet<V> valueSet( 452 @Nullable Comparator<? super V> valueComparator, 453 Collection<? extends V> values) { 454 return (valueComparator == null) 455 ? ImmutableSet.copyOf(values) 456 : ImmutableSortedSet.copyOf(valueComparator, values); 457 } 458 459 private static <V> ImmutableSet<V> emptySet( 460 @Nullable Comparator<? super V> valueComparator) { 461 return (valueComparator == null) 462 ? ImmutableSet.<V>of() 463 : ImmutableSortedSet.<V>emptySet(valueComparator); 464 } 465 466 @Nullable Comparator<? super V> valueComparator() { 467 return emptySet instanceof ImmutableSortedSet 468 ? ((ImmutableSortedSet<V>) emptySet).comparator() 469 : null; 470 } 471} 472 473