001 /*
002 * Copyright (C) 2009 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
017 package com.google.common.collect;
018
019 import static com.google.common.base.Preconditions.checkNotNull;
020
021 import com.google.common.annotations.Beta;
022 import com.google.common.annotations.GwtCompatible;
023 import com.google.common.annotations.GwtIncompatible;
024
025 import java.io.IOException;
026 import java.io.InvalidObjectException;
027 import java.io.ObjectInputStream;
028 import java.io.ObjectOutputStream;
029 import java.util.Arrays;
030 import java.util.Collection;
031 import java.util.Comparator;
032 import java.util.LinkedHashMap;
033 import java.util.Map;
034 import java.util.TreeMap;
035
036 import javax.annotation.Nullable;
037
038 /**
039 * An immutable {@link SetMultimap} with reliable user-specified key and value
040 * iteration order. Does not permit null keys or values.
041 *
042 * <p>Unlike {@link Multimaps#unmodifiableSetMultimap(SetMultimap)}, which is
043 * a <i>view</i> of a separate multimap which can still change, an instance of
044 * {@code ImmutableSetMultimap} contains its own data and will <i>never</i>
045 * change. {@code ImmutableSetMultimap} is convenient for
046 * {@code public static final} multimaps ("constant multimaps") and also lets
047 * you easily make a "defensive copy" of a multimap provided to your class by
048 * a caller.
049 *
050 * <p><b>Note</b>: Although this class is not final, it cannot be subclassed as
051 * it has no public or protected constructors. Thus, instances of this class
052 * are guaranteed to be immutable.
053 *
054 * @author Mike Ward
055 * @since 2 (imported from Google Collections Library)
056 */
057 @GwtCompatible(serializable = true, emulated = true)
058 public class ImmutableSetMultimap<K, V>
059 extends ImmutableMultimap<K, V>
060 implements SetMultimap<K, V> {
061
062 /** Returns the empty multimap. */
063 // Casting is safe because the multimap will never hold any elements.
064 @SuppressWarnings("unchecked")
065 public static <K, V> ImmutableSetMultimap<K, V> of() {
066 return (ImmutableSetMultimap<K, V>) EmptyImmutableSetMultimap.INSTANCE;
067 }
068
069 /**
070 * Returns an immutable multimap containing a single entry.
071 */
072 public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1) {
073 ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
074 builder.put(k1, v1);
075 return builder.build();
076 }
077
078 /**
079 * Returns an immutable multimap containing the given entries, in order.
080 * Repeated occurrences of an entry (according to {@link Object#equals}) after
081 * the first are ignored.
082 */
083 public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2) {
084 ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
085 builder.put(k1, v1);
086 builder.put(k2, v2);
087 return builder.build();
088 }
089
090 /**
091 * Returns an immutable multimap containing the given entries, in order.
092 * Repeated occurrences of an entry (according to {@link Object#equals}) after
093 * the first are ignored.
094 */
095 public static <K, V> ImmutableSetMultimap<K, V> of(
096 K k1, V v1, K k2, V v2, K k3, V v3) {
097 ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
098 builder.put(k1, v1);
099 builder.put(k2, v2);
100 builder.put(k3, v3);
101 return builder.build();
102 }
103
104 /**
105 * Returns an immutable multimap containing the given entries, in order.
106 * Repeated occurrences of an entry (according to {@link Object#equals}) after
107 * the first are ignored.
108 */
109 public static <K, V> ImmutableSetMultimap<K, V> of(
110 K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
111 ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
112 builder.put(k1, v1);
113 builder.put(k2, v2);
114 builder.put(k3, v3);
115 builder.put(k4, v4);
116 return builder.build();
117 }
118
119 /**
120 * Returns an immutable multimap containing the given entries, in order.
121 * Repeated occurrences of an entry (according to {@link Object#equals}) after
122 * the first are ignored.
123 */
124 public static <K, V> ImmutableSetMultimap<K, V> of(
125 K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
126 ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
127 builder.put(k1, v1);
128 builder.put(k2, v2);
129 builder.put(k3, v3);
130 builder.put(k4, v4);
131 builder.put(k5, v5);
132 return builder.build();
133 }
134
135 // looking for of() with > 5 entries? Use the builder instead.
136
137 /**
138 * Returns a new {@link Builder}.
139 */
140 public static <K, V> Builder<K, V> builder() {
141 return new Builder<K, V>();
142 }
143
144 /**
145 * Multimap for {@link ImmutableSetMultimap.Builder} that maintains key
146 * and value orderings and performs better than {@link LinkedHashMultimap}.
147 */
148 private static class BuilderMultimap<K, V> extends AbstractMultimap<K, V> {
149 BuilderMultimap() {
150 super(new LinkedHashMap<K, Collection<V>>());
151 }
152 @Override Collection<V> createCollection() {
153 return Sets.newLinkedHashSet();
154 }
155 private static final long serialVersionUID = 0;
156 }
157
158 /**
159 * Multimap for {@link ImmutableSetMultimap.Builder} that sorts keys and
160 * maintains value orderings.
161 */
162 private static class SortedKeyBuilderMultimap<K, V>
163 extends AbstractMultimap<K, V> {
164 SortedKeyBuilderMultimap(
165 Comparator<? super K> keyComparator, Multimap<K, V> multimap) {
166 super(new TreeMap<K, Collection<V>>(keyComparator));
167 putAll(multimap);
168 }
169 @Override Collection<V> createCollection() {
170 return Sets.newLinkedHashSet();
171 }
172 private static final long serialVersionUID = 0;
173 }
174
175 /**
176 * A builder for creating immutable {@code SetMultimap} instances, especially
177 * {@code public static final} multimaps ("constant multimaps"). Example:
178 * <pre> {@code
179 *
180 * static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP =
181 * new ImmutableSetMultimap.Builder<String, Integer>()
182 * .put("one", 1)
183 * .putAll("several", 1, 2, 3)
184 * .putAll("many", 1, 2, 3, 4, 5)
185 * .build();}</pre>
186 *
187 * Builder instances can be reused; it is safe to call {@link #build} multiple
188 * times to build multiple multimaps in series. Each multimap contains the
189 * key-value mappings in the previously created multimaps.
190 *
191 * @since 2 (imported from Google Collections Library)
192 */
193 public static final class Builder<K, V>
194 extends ImmutableMultimap.Builder<K, V> {
195 /**
196 * Creates a new builder. The returned builder is equivalent to the builder
197 * generated by {@link ImmutableSetMultimap#builder}.
198 */
199 public Builder() {
200 builderMultimap = new BuilderMultimap<K, V>();
201 }
202
203 /**
204 * Adds a key-value mapping to the built multimap if it is not already
205 * present.
206 */
207 @Override public Builder<K, V> put(K key, V value) {
208 builderMultimap.put(checkNotNull(key), checkNotNull(value));
209 return this;
210 }
211
212 @Override public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
213 Collection<V> collection = builderMultimap.get(checkNotNull(key));
214 for (V value : values) {
215 collection.add(checkNotNull(value));
216 }
217 return this;
218 }
219
220 @Override public Builder<K, V> putAll(K key, V... values) {
221 return putAll(key, Arrays.asList(values));
222 }
223
224 @Override public Builder<K, V> putAll(
225 Multimap<? extends K, ? extends V> multimap) {
226 for (Map.Entry<? extends K, ? extends Collection<? extends V>> entry
227 : multimap.asMap().entrySet()) {
228 putAll(entry.getKey(), entry.getValue());
229 }
230 return this;
231 }
232
233 /**
234 * {@inheritDoc}
235 *
236 * @since 8
237 */
238 @Beta @Override
239 public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) {
240 builderMultimap = new SortedKeyBuilderMultimap<K, V>(
241 checkNotNull(keyComparator), builderMultimap);
242 return this;
243 }
244
245 /**
246 * Specifies the ordering of the generated multimap's values for each key.
247 *
248 * <p>If this method is called, the sets returned by the {@code get()}
249 * method of the generated multimap and its {@link Multimap#asMap()} view
250 * are {@link ImmutableSortedSet} instances. However, serialization does not
251 * preserve that property, though it does maintain the key and value
252 * ordering.
253 *
254 * @since 8
255 */
256 // TODO: Make serialization behavior consistent.
257 @Beta @Override
258 public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
259 super.orderValuesBy(valueComparator);
260 return this;
261 }
262
263 /**
264 * Returns a newly-created immutable set multimap.
265 */
266 @Override public ImmutableSetMultimap<K, V> build() {
267 return copyOf(builderMultimap, valueComparator);
268 }
269 }
270
271 /**
272 * Returns an immutable set multimap containing the same mappings as
273 * {@code multimap}. The generated multimap's key and value orderings
274 * correspond to the iteration ordering of the {@code multimap.asMap()} view.
275 * Repeated occurrences of an entry in the multimap after the first are
276 * ignored.
277 *
278 * <p>Despite the method name, this method attempts to avoid actually copying
279 * the data when it is safe to do so. The exact circumstances under which a
280 * copy will or will not be performed are undocumented and subject to change.
281 *
282 * @throws NullPointerException if any key or value in {@code multimap} is
283 * null
284 */
285 public static <K, V> ImmutableSetMultimap<K, V> copyOf(
286 Multimap<? extends K, ? extends V> multimap) {
287 return copyOf(multimap, null);
288 }
289
290 private static <K, V> ImmutableSetMultimap<K, V> copyOf(
291 Multimap<? extends K, ? extends V> multimap,
292 Comparator<? super V> valueComparator) {
293 checkNotNull(multimap); // eager for GWT
294 if (multimap.isEmpty() && valueComparator == null) {
295 return of();
296 }
297
298 if (multimap instanceof ImmutableSetMultimap) {
299 @SuppressWarnings("unchecked") // safe since multimap is not writable
300 ImmutableSetMultimap<K, V> kvMultimap
301 = (ImmutableSetMultimap<K, V>) multimap;
302 if (!kvMultimap.isPartialView()) {
303 return kvMultimap;
304 }
305 }
306
307 ImmutableMap.Builder<K, ImmutableSet<V>> builder = ImmutableMap.builder();
308 int size = 0;
309
310 for (Map.Entry<? extends K, ? extends Collection<? extends V>> entry
311 : multimap.asMap().entrySet()) {
312 K key = entry.getKey();
313 Collection<? extends V> values = entry.getValue();
314 ImmutableSet<V> set = (valueComparator == null)
315 ? ImmutableSet.copyOf(values)
316 : ImmutableSortedSet.copyOf(valueComparator, values);
317 if (!set.isEmpty()) {
318 builder.put(key, set);
319 size += set.size();
320 }
321 }
322
323 return new ImmutableSetMultimap<K, V>(
324 builder.build(), size, valueComparator);
325 }
326
327 // Returned by get() when values are sorted and a missing key is provided.
328 private final transient ImmutableSortedSet<V> emptySet;
329
330 ImmutableSetMultimap(ImmutableMap<K, ImmutableSet<V>> map, int size,
331 @Nullable Comparator<? super V> valueComparator) {
332 super(map, size);
333 this.emptySet = (valueComparator == null)
334 ? null : ImmutableSortedSet.<V>emptySet(valueComparator);
335 }
336
337 // views
338
339 /**
340 * Returns an immutable set of the values for the given key. If no mappings
341 * in the multimap have the provided key, an empty immutable set is returned.
342 * The values are in the same order as the parameters used to build this
343 * multimap.
344 */
345 @Override public ImmutableSet<V> get(@Nullable K key) {
346 // This cast is safe as its type is known in constructor.
347 ImmutableSet<V> set = (ImmutableSet<V>) map.get(key);
348 if (set != null) {
349 return set;
350 } else if (emptySet != null) {
351 return emptySet;
352 } else {
353 return ImmutableSet.<V>of();
354 }
355 }
356
357 /**
358 * Guaranteed to throw an exception and leave the multimap unmodified.
359 *
360 * @throws UnsupportedOperationException always
361 */
362 @Override public ImmutableSet<V> removeAll(Object key) {
363 throw new UnsupportedOperationException();
364 }
365
366 /**
367 * Guaranteed to throw an exception and leave the multimap unmodified.
368 *
369 * @throws UnsupportedOperationException always
370 */
371 @Override public ImmutableSet<V> replaceValues(
372 K key, Iterable<? extends V> values) {
373 throw new UnsupportedOperationException();
374 }
375
376 private transient ImmutableSet<Map.Entry<K, V>> entries;
377
378 /**
379 * Returns an immutable collection of all key-value pairs in the multimap.
380 * Its iterator traverses the values for the first key, the values for the
381 * second key, and so on.
382 */
383 // TODO(kevinb): Fix this so that two copies of the entries are not created.
384 @Override public ImmutableSet<Map.Entry<K, V>> entries() {
385 ImmutableSet<Map.Entry<K, V>> result = entries;
386 return (result == null)
387 ? (entries = ImmutableSet.copyOf(super.entries()))
388 : result;
389 }
390
391 /**
392 * @serialData number of distinct keys, and then for each distinct key: the
393 * key, the number of values for that key, and the key's values
394 */
395 @GwtIncompatible("java.io.ObjectOutputStream")
396 private void writeObject(ObjectOutputStream stream) throws IOException {
397 stream.defaultWriteObject();
398 Serialization.writeMultimap(this, stream);
399 }
400
401 @GwtIncompatible("java.io.ObjectInputStream")
402 private void readObject(ObjectInputStream stream)
403 throws IOException, ClassNotFoundException {
404 stream.defaultReadObject();
405 int keyCount = stream.readInt();
406 if (keyCount < 0) {
407 throw new InvalidObjectException("Invalid key count " + keyCount);
408 }
409 ImmutableMap.Builder<Object, ImmutableSet<Object>> builder
410 = ImmutableMap.builder();
411 int tmpSize = 0;
412
413 for (int i = 0; i < keyCount; i++) {
414 Object key = stream.readObject();
415 int valueCount = stream.readInt();
416 if (valueCount <= 0) {
417 throw new InvalidObjectException("Invalid value count " + valueCount);
418 }
419
420 Object[] array = new Object[valueCount];
421 for (int j = 0; j < valueCount; j++) {
422 array[j] = stream.readObject();
423 }
424 ImmutableSet<Object> valueSet = ImmutableSet.copyOf(array);
425 if (valueSet.size() != array.length) {
426 throw new InvalidObjectException(
427 "Duplicate key-value pairs exist for key " + key);
428 }
429 builder.put(key, valueSet);
430 tmpSize += valueCount;
431 }
432
433 ImmutableMap<Object, ImmutableSet<Object>> tmpMap;
434 try {
435 tmpMap = builder.build();
436 } catch (IllegalArgumentException e) {
437 throw (InvalidObjectException)
438 new InvalidObjectException(e.getMessage()).initCause(e);
439 }
440
441 FieldSettersHolder.MAP_FIELD_SETTER.set(this, tmpMap);
442 FieldSettersHolder.SIZE_FIELD_SETTER.set(this, tmpSize);
443 }
444
445 @GwtIncompatible("not needed in emulated source.")
446 private static final long serialVersionUID = 0;
447 }