001/* 002 * Copyright (C) 2013 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; 020import static com.google.common.collect.CollectPreconditions.checkNonnegative; 021import static com.google.common.collect.Maps.newLinkedHashMapWithExpectedSize; 022 023import com.google.common.annotations.Beta; 024import com.google.common.annotations.GwtCompatible; 025import com.google.common.base.Supplier; 026import java.io.Serializable; 027import java.util.ArrayList; 028import java.util.Collection; 029import java.util.Comparator; 030import java.util.EnumMap; 031import java.util.EnumSet; 032import java.util.HashMap; 033import java.util.HashSet; 034import java.util.LinkedHashMap; 035import java.util.LinkedHashSet; 036import java.util.LinkedList; 037import java.util.List; 038import java.util.Map; 039import java.util.Set; 040import java.util.SortedSet; 041import java.util.TreeMap; 042import java.util.TreeSet; 043 044/** 045 * A builder for a multimap implementation that allows customization of the backing map and value 046 * collection implementations used in a particular multimap. 047 * 048 * <p>This can be used to easily configure multimap data structure implementations not provided 049 * explicitly in {@code com.google.common.collect}, for example: 050 * 051 * <pre> {@code 052 * ListMultimap<String, Integer> treeListMultimap = 053 * MultimapBuilder.treeKeys().arrayListValues().build(); 054 * SetMultimap<Integer, MyEnum> hashEnumMultimap = 055 * MultimapBuilder.hashKeys().enumSetValues(MyEnum.class).build();}</pre> 056 * 057 * <p>{@code MultimapBuilder} instances are immutable. Invoking a configuration method has no 058 * effect on the receiving instance; you must store and use the new builder instance it returns 059 * instead. 060 * 061 * <p>The generated multimaps are serializable if the key and value types are serializable, 062 * unless stated otherwise in one of the configuration methods. 063 * 064 * @author Louis Wasserman 065 * @param <K0> An upper bound on the key type of the generated multimap. 066 * @param <V0> An upper bound on the value type of the generated multimap. 067 * @since 16.0 068 */ 069@Beta 070@GwtCompatible 071public abstract class MultimapBuilder<K0, V0> { 072 /* 073 * Leaving K and V as upper bounds rather than the actual key and value types allows type 074 * parameters to be left implicit more often. CacheBuilder uses the same technique. 075 */ 076 077 private MultimapBuilder() {} 078 079 private static final int DEFAULT_EXPECTED_KEYS = 8; 080 081 /** 082 * Uses a {@link HashMap} to map keys to value collections. 083 */ 084 public static MultimapBuilderWithKeys<Object> hashKeys() { 085 return hashKeys(DEFAULT_EXPECTED_KEYS); 086 } 087 088 /** 089 * Uses a {@link HashMap} to map keys to value collections, initialized to expect the specified 090 * number of keys. 091 * 092 * @throws IllegalArgumentException if {@code expectedKeys < 0} 093 */ 094 public static MultimapBuilderWithKeys<Object> hashKeys(final int expectedKeys) { 095 checkNonnegative(expectedKeys, "expectedKeys"); 096 return new MultimapBuilderWithKeys<Object>() { 097 @Override 098 <K, V> Map<K, Collection<V>> createMap() { 099 return Maps.newHashMapWithExpectedSize(expectedKeys); 100 } 101 }; 102 } 103 104 /** 105 * Uses a {@link LinkedHashMap} to map keys to value collections. 106 * 107 * <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and 108 * {@link Multimap#asMap()} will iterate through the keys in the order that they were first added 109 * to the multimap, save that if all values associated with a key are removed and then the key is 110 * added back into the multimap, that key will come last in the key iteration order. 111 */ 112 public static MultimapBuilderWithKeys<Object> linkedHashKeys() { 113 return linkedHashKeys(DEFAULT_EXPECTED_KEYS); 114 } 115 116 /** 117 * Uses a {@link LinkedHashMap} to map keys to value collections, initialized to expect the 118 * specified number of keys. 119 * 120 * <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and 121 * {@link Multimap#asMap()} will iterate through the keys in the order that they were first added 122 * to the multimap, save that if all values associated with a key are removed and then the key is 123 * added back into the multimap, that key will come last in the key iteration order. 124 */ 125 public static MultimapBuilderWithKeys<Object> linkedHashKeys(final int expectedKeys) { 126 checkNonnegative(expectedKeys, "expectedKeys"); 127 return new MultimapBuilderWithKeys<Object>() { 128 @Override 129 <K, V> Map<K, Collection<V>> createMap() { 130 return newLinkedHashMapWithExpectedSize(expectedKeys); 131 } 132 }; 133 } 134 135 /** 136 * Uses a naturally-ordered {@link TreeMap} to map keys to value collections. 137 * 138 * <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and 139 * {@link Multimap#asMap()} will iterate through the keys in sorted order. 140 * 141 * <p>For all multimaps generated by the resulting builder, the {@link Multimap#keySet()} can be 142 * safely cast to a {@link java.util.SortedSet}, and the {@link Multimap#asMap()} can safely be 143 * cast to a {@link java.util.SortedMap}. 144 */ 145 @SuppressWarnings("rawtypes") 146 public static MultimapBuilderWithKeys<Comparable> treeKeys() { 147 return treeKeys(Ordering.natural()); 148 } 149 150 /** 151 * Uses a {@link TreeMap} sorted by the specified comparator to map keys to value collections. 152 * 153 * <p>The collections returned by {@link Multimap#keySet()}, {@link Multimap#keys()}, and 154 * {@link Multimap#asMap()} will iterate through the keys in sorted order. 155 * 156 * <p>For all multimaps generated by the resulting builder, the {@link Multimap#keySet()} can be 157 * safely cast to a {@link java.util.SortedSet}, and the {@link Multimap#asMap()} can safely be 158 * cast to a {@link java.util.SortedMap}. 159 * 160 * <p>Multimaps generated by the resulting builder will not be serializable if {@code comparator} 161 * is not serializable. 162 */ 163 public static <K0> MultimapBuilderWithKeys<K0> treeKeys(final Comparator<K0> comparator) { 164 checkNotNull(comparator); 165 return new MultimapBuilderWithKeys<K0>() { 166 @Override 167 <K extends K0, V> Map<K, Collection<V>> createMap() { 168 return new TreeMap<K, Collection<V>>(comparator); 169 } 170 }; 171 } 172 173 /** 174 * Uses an {@link EnumMap} to map keys to value collections. 175 */ 176 public static <K0 extends Enum<K0>> MultimapBuilderWithKeys<K0> enumKeys( 177 final Class<K0> keyClass) { 178 checkNotNull(keyClass); 179 return new MultimapBuilderWithKeys<K0>() { 180 @SuppressWarnings("unchecked") 181 @Override 182 <K extends K0, V> Map<K, Collection<V>> createMap() { 183 // K must actually be K0, since enums are effectively final 184 // (their subclasses are inaccessible) 185 return (Map<K, Collection<V>>) new EnumMap<K0, Collection<V>>(keyClass); 186 } 187 }; 188 } 189 190 private static final class ArrayListSupplier<V> implements Supplier<List<V>>, Serializable { 191 private final int expectedValuesPerKey; 192 193 ArrayListSupplier(int expectedValuesPerKey) { 194 this.expectedValuesPerKey = checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey"); 195 } 196 197 @Override 198 public List<V> get() { 199 return new ArrayList<V>(expectedValuesPerKey); 200 } 201 } 202 203 private enum LinkedListSupplier implements Supplier<List<Object>> { 204 INSTANCE; 205 206 public static <V> Supplier<List<V>> instance() { 207 // Each call generates a fresh LinkedList, which can serve as a List<V> for any V. 208 @SuppressWarnings({"rawtypes", "unchecked"}) 209 Supplier<List<V>> result = (Supplier) INSTANCE; 210 return result; 211 } 212 213 @Override 214 public List<Object> get() { 215 return new LinkedList<Object>(); 216 } 217 } 218 219 private static final class HashSetSupplier<V> implements Supplier<Set<V>>, Serializable { 220 private final int expectedValuesPerKey; 221 222 HashSetSupplier(int expectedValuesPerKey) { 223 this.expectedValuesPerKey = checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey"); 224 } 225 226 @Override 227 public Set<V> get() { 228 return Sets.newHashSetWithExpectedSize(expectedValuesPerKey); 229 } 230 } 231 232 private static final class LinkedHashSetSupplier<V> implements Supplier<Set<V>>, Serializable { 233 private final int expectedValuesPerKey; 234 235 LinkedHashSetSupplier(int expectedValuesPerKey) { 236 this.expectedValuesPerKey = checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey"); 237 } 238 239 @Override 240 public Set<V> get() { 241 return Sets.newLinkedHashSetWithExpectedSize(expectedValuesPerKey); 242 } 243 } 244 245 private static final class TreeSetSupplier<V> implements Supplier<SortedSet<V>>, Serializable { 246 private final Comparator<? super V> comparator; 247 248 TreeSetSupplier(Comparator<? super V> comparator) { 249 this.comparator = checkNotNull(comparator); 250 } 251 252 @Override 253 public SortedSet<V> get() { 254 return new TreeSet<V>(comparator); 255 } 256 } 257 258 private static final class EnumSetSupplier<V extends Enum<V>> 259 implements Supplier<Set<V>>, Serializable { 260 private final Class<V> clazz; 261 262 EnumSetSupplier(Class<V> clazz) { 263 this.clazz = checkNotNull(clazz); 264 } 265 266 @Override 267 public Set<V> get() { 268 return EnumSet.noneOf(clazz); 269 } 270 } 271 272 /** 273 * An intermediate stage in a {@link MultimapBuilder} in which the key-value collection map 274 * implementation has been specified, but the value collection implementation has not. 275 * 276 * @param <K0> The upper bound on the key type of the generated multimap. 277 */ 278 public abstract static class MultimapBuilderWithKeys<K0> { 279 280 private static final int DEFAULT_EXPECTED_VALUES_PER_KEY = 2; 281 282 MultimapBuilderWithKeys() {} 283 284 abstract <K extends K0, V> Map<K, Collection<V>> createMap(); 285 286 /** 287 * Uses an {@link ArrayList} to store value collections. 288 */ 289 public ListMultimapBuilder<K0, Object> arrayListValues() { 290 return arrayListValues(DEFAULT_EXPECTED_VALUES_PER_KEY); 291 } 292 293 /** 294 * Uses an {@link ArrayList} to store value collections, initialized to expect the specified 295 * number of values per key. 296 * 297 * @throws IllegalArgumentException if {@code expectedValuesPerKey < 0} 298 */ 299 public ListMultimapBuilder<K0, Object> arrayListValues(final int expectedValuesPerKey) { 300 checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey"); 301 return new ListMultimapBuilder<K0, Object>() { 302 @Override 303 public <K extends K0, V> ListMultimap<K, V> build() { 304 return Multimaps.newListMultimap( 305 MultimapBuilderWithKeys.this.<K, V>createMap(), 306 new ArrayListSupplier<V>(expectedValuesPerKey)); 307 } 308 }; 309 } 310 311 /** 312 * Uses a {@link LinkedList} to store value collections. 313 */ 314 public ListMultimapBuilder<K0, Object> linkedListValues() { 315 return new ListMultimapBuilder<K0, Object>() { 316 @Override 317 public <K extends K0, V> ListMultimap<K, V> build() { 318 return Multimaps.newListMultimap( 319 MultimapBuilderWithKeys.this.<K, V>createMap(), LinkedListSupplier.<V>instance()); 320 } 321 }; 322 } 323 324 /** 325 * Uses a {@link HashSet} to store value collections. 326 */ 327 public SetMultimapBuilder<K0, Object> hashSetValues() { 328 return hashSetValues(DEFAULT_EXPECTED_VALUES_PER_KEY); 329 } 330 331 /** 332 * Uses a {@link HashSet} to store value collections, initialized to expect the specified number 333 * of values per key. 334 * 335 * @throws IllegalArgumentException if {@code expectedValuesPerKey < 0} 336 */ 337 public SetMultimapBuilder<K0, Object> hashSetValues(final int expectedValuesPerKey) { 338 checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey"); 339 return new SetMultimapBuilder<K0, Object>() { 340 @Override 341 public <K extends K0, V> SetMultimap<K, V> build() { 342 return Multimaps.newSetMultimap( 343 MultimapBuilderWithKeys.this.<K, V>createMap(), 344 new HashSetSupplier<V>(expectedValuesPerKey)); 345 } 346 }; 347 } 348 349 /** 350 * Uses a {@link LinkedHashSet} to store value collections. 351 */ 352 public SetMultimapBuilder<K0, Object> linkedHashSetValues() { 353 return linkedHashSetValues(DEFAULT_EXPECTED_VALUES_PER_KEY); 354 } 355 356 /** 357 * Uses a {@link LinkedHashSet} to store value collections, initialized to expect the specified 358 * number of values per key. 359 * 360 * @throws IllegalArgumentException if {@code expectedValuesPerKey < 0} 361 */ 362 public SetMultimapBuilder<K0, Object> linkedHashSetValues(final int expectedValuesPerKey) { 363 checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey"); 364 return new SetMultimapBuilder<K0, Object>() { 365 @Override 366 public <K extends K0, V> SetMultimap<K, V> build() { 367 return Multimaps.newSetMultimap( 368 MultimapBuilderWithKeys.this.<K, V>createMap(), 369 new LinkedHashSetSupplier<V>(expectedValuesPerKey)); 370 } 371 }; 372 } 373 374 /** 375 * Uses a naturally-ordered {@link TreeSet} to store value collections. 376 */ 377 @SuppressWarnings("rawtypes") 378 public SortedSetMultimapBuilder<K0, Comparable> treeSetValues() { 379 return treeSetValues(Ordering.natural()); 380 } 381 382 /** 383 * Uses a {@link TreeSet} ordered by the specified comparator to store value collections. 384 * 385 * <p>Multimaps generated by the resulting builder will not be serializable if 386 * {@code comparator} is not serializable. 387 */ 388 public <V0> SortedSetMultimapBuilder<K0, V0> treeSetValues(final Comparator<V0> comparator) { 389 checkNotNull(comparator, "comparator"); 390 return new SortedSetMultimapBuilder<K0, V0>() { 391 @Override 392 public <K extends K0, V extends V0> SortedSetMultimap<K, V> build() { 393 return Multimaps.newSortedSetMultimap( 394 MultimapBuilderWithKeys.this.<K, V>createMap(), new TreeSetSupplier<V>(comparator)); 395 } 396 }; 397 } 398 399 /** 400 * Uses an {@link EnumSet} to store value collections. 401 */ 402 public <V0 extends Enum<V0>> SetMultimapBuilder<K0, V0> enumSetValues( 403 final Class<V0> valueClass) { 404 checkNotNull(valueClass, "valueClass"); 405 return new SetMultimapBuilder<K0, V0>() { 406 @Override 407 public <K extends K0, V extends V0> SetMultimap<K, V> build() { 408 // V must actually be V0, since enums are effectively final 409 // (their subclasses are inaccessible) 410 @SuppressWarnings({"unchecked", "rawtypes"}) 411 Supplier<Set<V>> factory = (Supplier) new EnumSetSupplier<V0>(valueClass); 412 return Multimaps.newSetMultimap(MultimapBuilderWithKeys.this.<K, V>createMap(), factory); 413 } 414 }; 415 } 416 } 417 418 /** 419 * Returns a new, empty {@code Multimap} with the specified implementation. 420 */ 421 public abstract <K extends K0, V extends V0> Multimap<K, V> build(); 422 423 /** 424 * Returns a {@code Multimap} with the specified implementation, initialized with the entries of 425 * {@code multimap}. 426 */ 427 public <K extends K0, V extends V0> Multimap<K, V> build( 428 Multimap<? extends K, ? extends V> multimap) { 429 Multimap<K, V> result = build(); 430 result.putAll(multimap); 431 return result; 432 } 433 434 /** 435 * A specialization of {@link MultimapBuilder} that generates {@link ListMultimap} instances. 436 */ 437 public abstract static class ListMultimapBuilder<K0, V0> extends MultimapBuilder<K0, V0> { 438 ListMultimapBuilder() {} 439 440 @Override 441 public abstract <K extends K0, V extends V0> ListMultimap<K, V> build(); 442 443 @Override 444 public <K extends K0, V extends V0> ListMultimap<K, V> build( 445 Multimap<? extends K, ? extends V> multimap) { 446 return (ListMultimap<K, V>) super.build(multimap); 447 } 448 } 449 450 /** 451 * A specialization of {@link MultimapBuilder} that generates {@link SetMultimap} instances. 452 */ 453 public abstract static class SetMultimapBuilder<K0, V0> extends MultimapBuilder<K0, V0> { 454 SetMultimapBuilder() {} 455 456 @Override 457 public abstract <K extends K0, V extends V0> SetMultimap<K, V> build(); 458 459 @Override 460 public <K extends K0, V extends V0> SetMultimap<K, V> build( 461 Multimap<? extends K, ? extends V> multimap) { 462 return (SetMultimap<K, V>) super.build(multimap); 463 } 464 } 465 466 /** 467 * A specialization of {@link MultimapBuilder} that generates {@link SortedSetMultimap} instances. 468 */ 469 public abstract static class SortedSetMultimapBuilder<K0, V0> extends SetMultimapBuilder<K0, V0> { 470 SortedSetMultimapBuilder() {} 471 472 @Override 473 public abstract <K extends K0, V extends V0> SortedSetMultimap<K, V> build(); 474 475 @Override 476 public <K extends K0, V extends V0> SortedSetMultimap<K, V> build( 477 Multimap<? extends K, ? extends V> multimap) { 478 return (SortedSetMultimap<K, V>) super.build(multimap); 479 } 480 } 481}