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
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.Function;
025
026import java.io.IOException;
027import java.io.InvalidObjectException;
028import java.io.ObjectInputStream;
029import java.io.ObjectOutputStream;
030import java.util.Arrays;
031import java.util.Collection;
032import java.util.Collections;
033import java.util.Comparator;
034import java.util.LinkedHashMap;
035import java.util.List;
036import java.util.Map;
037import java.util.Map.Entry;
038import java.util.TreeMap;
039
040import javax.annotation.Nullable;
041
042/**
043 * An immutable {@link SetMultimap} with reliable user-specified key and value
044 * iteration order. Does not permit null keys or values.
045 *
046 * <p>Unlike {@link Multimaps#unmodifiableSetMultimap(SetMultimap)}, which is
047 * a <i>view</i> of a separate multimap which can still change, an instance of
048 * {@code ImmutableSetMultimap} contains its own data and will <i>never</i>
049 * change. {@code ImmutableSetMultimap} is convenient for
050 * {@code public static final} multimaps ("constant multimaps") and also lets
051 * you easily make a "defensive copy" of a multimap provided to your class by
052 * a caller.
053 *
054 * <p><b>Note:</b> Although this class is not final, it cannot be subclassed as
055 * it has no public or protected constructors. Thus, instances of this class
056 * are guaranteed to be immutable.
057 *
058 * <p>See the Guava User Guide article on <a href=
059 * "http://code.google.com/p/guava-libraries/wiki/ImmutableCollectionsExplained">
060 * immutable collections</a>.
061 *
062 * @author Mike Ward
063 * @since 2.0 (imported from Google Collections Library)
064 */
065@GwtCompatible(serializable = true, emulated = true)
066public class ImmutableSetMultimap<K, V>
067    extends ImmutableMultimap<K, V>
068    implements SetMultimap<K, V> {
069
070  /** Returns the empty multimap. */
071  // Casting is safe because the multimap will never hold any elements.
072  @SuppressWarnings("unchecked")
073  public static <K, V> ImmutableSetMultimap<K, V> of() {
074    return (ImmutableSetMultimap<K, V>) EmptyImmutableSetMultimap.INSTANCE;
075  }
076
077  /**
078   * Returns an immutable multimap containing a single entry.
079   */
080  public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1) {
081    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
082    builder.put(k1, v1);
083    return builder.build();
084  }
085
086  /**
087   * Returns an immutable multimap containing the given entries, in order.
088   * Repeated occurrences of an entry (according to {@link Object#equals}) after
089   * the first are ignored.
090   */
091  public static <K, V> ImmutableSetMultimap<K, V> of(K k1, V v1, K k2, V v2) {
092    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
093    builder.put(k1, v1);
094    builder.put(k2, v2);
095    return builder.build();
096  }
097
098  /**
099   * Returns an immutable multimap containing the given entries, in order.
100   * Repeated occurrences of an entry (according to {@link Object#equals}) after
101   * the first are ignored.
102   */
103  public static <K, V> ImmutableSetMultimap<K, V> of(
104      K k1, V v1, K k2, V v2, K k3, V v3) {
105    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
106    builder.put(k1, v1);
107    builder.put(k2, v2);
108    builder.put(k3, v3);
109    return builder.build();
110  }
111
112  /**
113   * Returns an immutable multimap containing the given entries, in order.
114   * Repeated occurrences of an entry (according to {@link Object#equals}) after
115   * the first are ignored.
116   */
117  public static <K, V> ImmutableSetMultimap<K, V> of(
118      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
119    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
120    builder.put(k1, v1);
121    builder.put(k2, v2);
122    builder.put(k3, v3);
123    builder.put(k4, v4);
124    return builder.build();
125  }
126
127  /**
128   * Returns an immutable multimap containing the given entries, in order.
129   * Repeated occurrences of an entry (according to {@link Object#equals}) after
130   * the first are ignored.
131   */
132  public static <K, V> ImmutableSetMultimap<K, V> of(
133      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
134    ImmutableSetMultimap.Builder<K, V> builder = ImmutableSetMultimap.builder();
135    builder.put(k1, v1);
136    builder.put(k2, v2);
137    builder.put(k3, v3);
138    builder.put(k4, v4);
139    builder.put(k5, v5);
140    return builder.build();
141  }
142
143  // looking for of() with > 5 entries? Use the builder instead.
144
145  /**
146   * Returns a new {@link Builder}.
147   */
148  public static <K, V> Builder<K, V> builder() {
149    return new Builder<K, V>();
150  }
151
152  /**
153   * Multimap for {@link ImmutableSetMultimap.Builder} that maintains key
154   * and value orderings and performs better than {@link LinkedHashMultimap}.
155   */
156  private static class BuilderMultimap<K, V> extends AbstractMultimap<K, V> {
157    BuilderMultimap() {
158      super(new LinkedHashMap<K, Collection<V>>());
159    }
160    @Override Collection<V> createCollection() {
161      return Sets.newLinkedHashSet();
162    }
163    private static final long serialVersionUID = 0;
164  }
165
166  /**
167   * Multimap for {@link ImmutableSetMultimap.Builder} that sorts keys and
168   * maintains value orderings.
169   */
170  private static class SortedKeyBuilderMultimap<K, V>
171      extends AbstractMultimap<K, V> {
172    SortedKeyBuilderMultimap(
173        Comparator<? super K> keyComparator, Multimap<K, V> multimap) {
174      super(new TreeMap<K, Collection<V>>(keyComparator));
175      putAll(multimap);
176    }
177    @Override Collection<V> createCollection() {
178      return Sets.newLinkedHashSet();
179    }
180    private static final long serialVersionUID = 0;
181  }
182
183  /**
184   * A builder for creating immutable {@code SetMultimap} instances, especially
185   * {@code public static final} multimaps ("constant multimaps"). Example:
186   * <pre>   {@code
187   *
188   *   static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP =
189   *       new ImmutableSetMultimap.Builder<String, Integer>()
190   *           .put("one", 1)
191   *           .putAll("several", 1, 2, 3)
192   *           .putAll("many", 1, 2, 3, 4, 5)
193   *           .build();}</pre>
194   *
195   * Builder instances can be reused; it is safe to call {@link #build} multiple
196   * times to build multiple multimaps in series. Each multimap contains the
197   * key-value mappings in the previously created multimaps.
198   *
199   * @since 2.0 (imported from Google Collections Library)
200   */
201  public static final class Builder<K, V>
202      extends ImmutableMultimap.Builder<K, V> {
203    /**
204     * Creates a new builder. The returned builder is equivalent to the builder
205     * generated by {@link ImmutableSetMultimap#builder}.
206     */
207    public Builder() {
208      builderMultimap = new BuilderMultimap<K, V>();
209    }
210
211    /**
212     * Adds a key-value mapping to the built multimap if it is not already
213     * present.
214     */
215    @Override public Builder<K, V> put(K key, V value) {
216      builderMultimap.put(checkNotNull(key), checkNotNull(value));
217      return this;
218    }
219
220    /**
221     * Adds an entry to the built multimap if it is not already present.
222     *
223     * @since 11.0
224     */
225    @Override public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
226      builderMultimap.put(
227          checkNotNull(entry.getKey()), checkNotNull(entry.getValue()));
228      return this;
229    }
230
231    @Override public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
232      Collection<V> collection = builderMultimap.get(checkNotNull(key));
233      for (V value : values) {
234        collection.add(checkNotNull(value));
235      }
236      return this;
237    }
238
239    @Override public Builder<K, V> putAll(K key, V... values) {
240      return putAll(key, Arrays.asList(values));
241    }
242
243    @Override public Builder<K, V> putAll(
244        Multimap<? extends K, ? extends V> multimap) {
245      for (Entry<? extends K, ? extends Collection<? extends V>> entry
246          : multimap.asMap().entrySet()) {
247        putAll(entry.getKey(), entry.getValue());
248      }
249      return this;
250    }
251
252    /**
253     * {@inheritDoc}
254     *
255     * @since 8.0
256     */
257    @Beta @Override
258    public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) {
259      this.keyComparator = checkNotNull(keyComparator);
260      return this;
261    }
262
263    /**
264     * Specifies the ordering of the generated multimap's values for each key.
265     *
266     * <p>If this method is called, the sets returned by the {@code get()}
267     * method of the generated multimap and its {@link Multimap#asMap()} view
268     * are {@link ImmutableSortedSet} instances. However, serialization does not
269     * preserve that property, though it does maintain the key and value
270     * ordering.
271     *
272     * @since 8.0
273     */
274    // TODO: Make serialization behavior consistent.
275    @Beta @Override
276    public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
277      super.orderValuesBy(valueComparator);
278      return this;
279    }
280
281    /**
282     * Returns a newly-created immutable set multimap.
283     */
284    @Override public ImmutableSetMultimap<K, V> build() {
285      if (keyComparator != null) {
286        Multimap<K, V> sortedCopy = new BuilderMultimap<K, V>();
287        List<Map.Entry<K, Collection<V>>> entries = Lists.newArrayList(
288            builderMultimap.asMap().entrySet());
289        Collections.sort(
290            entries,
291            Ordering.from(keyComparator).onResultOf(new Function<Entry<K, Collection<V>>, K>() {
292              @Override
293              public K apply(Entry<K, Collection<V>> entry) {
294                return entry.getKey();
295              }
296            }));
297        for (Map.Entry<K, Collection<V>> entry : entries) {
298          sortedCopy.putAll(entry.getKey(), entry.getValue());
299        }
300        builderMultimap = sortedCopy;
301      }
302      return copyOf(builderMultimap, valueComparator);
303    }
304  }
305
306  /**
307   * Returns an immutable set multimap containing the same mappings as
308   * {@code multimap}. The generated multimap's key and value orderings
309   * correspond to the iteration ordering of the {@code multimap.asMap()} view.
310   * Repeated occurrences of an entry in the multimap after the first are
311   * ignored.
312   *
313   * <p>Despite the method name, this method attempts to avoid actually copying
314   * the data when it is safe to do so. The exact circumstances under which a
315   * copy will or will not be performed are undocumented and subject to change.
316   *
317   * @throws NullPointerException if any key or value in {@code multimap} is
318   *     null
319   */
320  public static <K, V> ImmutableSetMultimap<K, V> copyOf(
321      Multimap<? extends K, ? extends V> multimap) {
322    return copyOf(multimap, null);
323  }
324
325  private static <K, V> ImmutableSetMultimap<K, V> copyOf(
326      Multimap<? extends K, ? extends V> multimap,
327      Comparator<? super V> valueComparator) {
328    checkNotNull(multimap); // eager for GWT
329    if (multimap.isEmpty() && valueComparator == null) {
330      return of();
331    }
332
333    if (multimap instanceof ImmutableSetMultimap) {
334      @SuppressWarnings("unchecked") // safe since multimap is not writable
335      ImmutableSetMultimap<K, V> kvMultimap
336          = (ImmutableSetMultimap<K, V>) multimap;
337      if (!kvMultimap.isPartialView()) {
338        return kvMultimap;
339      }
340    }
341
342    ImmutableMap.Builder<K, ImmutableSet<V>> builder = ImmutableMap.builder();
343    int size = 0;
344
345    for (Entry<? extends K, ? extends Collection<? extends V>> entry
346        : multimap.asMap().entrySet()) {
347      K key = entry.getKey();
348      Collection<? extends V> values = entry.getValue();
349      ImmutableSet<V> set = (valueComparator == null)
350          ? ImmutableSet.copyOf(values)
351          : ImmutableSortedSet.copyOf(valueComparator, values);
352      if (!set.isEmpty()) {
353        builder.put(key, set);
354        size += set.size();
355      }
356    }
357
358    return new ImmutableSetMultimap<K, V>(
359        builder.build(), size, valueComparator);
360  }
361
362  // Returned by get() when values are sorted and a missing key is provided.
363  private final transient ImmutableSortedSet<V> emptySet;
364
365  ImmutableSetMultimap(ImmutableMap<K, ImmutableSet<V>> map, int size,
366      @Nullable Comparator<? super V> valueComparator) {
367    super(map, size);
368    this.emptySet = (valueComparator == null)
369        ? null : ImmutableSortedSet.<V>emptySet(valueComparator);
370  }
371
372  // views
373
374  /**
375   * Returns an immutable set of the values for the given key.  If no mappings
376   * in the multimap have the provided key, an empty immutable set is returned.
377   * The values are in the same order as the parameters used to build this
378   * multimap.
379   */
380  @Override public ImmutableSet<V> get(@Nullable K key) {
381    // This cast is safe as its type is known in constructor.
382    ImmutableSet<V> set = (ImmutableSet<V>) map.get(key);
383    if (set != null) {
384      return set;
385    } else if (emptySet != null) {
386      return emptySet;
387    } else {
388      return ImmutableSet.<V>of();
389    }
390  }
391
392  private transient ImmutableSetMultimap<V, K> inverse;
393
394  /**
395   * {@inheritDoc}
396   *
397   * <p>Because an inverse of a set multimap cannot contain multiple pairs with
398   * the same key and value, this method returns an {@code ImmutableSetMultimap}
399   * rather than the {@code ImmutableMultimap} specified in the {@code
400   * ImmutableMultimap} class.
401   *
402   * @since 11.0
403   */
404  @Beta
405  public ImmutableSetMultimap<V, K> inverse() {
406    ImmutableSetMultimap<V, K> result = inverse;
407    return (result == null) ? (inverse = invert()) : result;
408  }
409
410  private ImmutableSetMultimap<V, K> invert() {
411    Builder<V, K> builder = builder();
412    for (Entry<K, V> entry : entries()) {
413      builder.put(entry.getValue(), entry.getKey());
414    }
415    ImmutableSetMultimap<V, K> invertedMultimap = builder.build();
416    invertedMultimap.inverse = this;
417    return invertedMultimap;
418  }
419
420  /**
421   * Guaranteed to throw an exception and leave the multimap unmodified.
422   *
423   * @throws UnsupportedOperationException always
424   */
425  @Override public ImmutableSet<V> removeAll(Object key) {
426    throw new UnsupportedOperationException();
427  }
428
429  /**
430   * Guaranteed to throw an exception and leave the multimap unmodified.
431   *
432   * @throws UnsupportedOperationException always
433   */
434  @Override public ImmutableSet<V> replaceValues(
435      K key, Iterable<? extends V> values) {
436    throw new UnsupportedOperationException();
437  }
438
439  private transient ImmutableSet<Entry<K, V>> entries;
440
441  /**
442   * Returns an immutable collection of all key-value pairs in the multimap.
443   * Its iterator traverses the values for the first key, the values for the
444   * second key, and so on.
445   */
446  // TODO(kevinb): Fix this so that two copies of the entries are not created.
447  @Override public ImmutableSet<Entry<K, V>> entries() {
448    ImmutableSet<Entry<K, V>> result = entries;
449    return (result == null)
450        ? (entries = ImmutableSet.copyOf(super.entries()))
451        : result;
452  }
453
454  /**
455   * @serialData number of distinct keys, and then for each distinct key: the
456   *     key, the number of values for that key, and the key's values
457   */
458  @GwtIncompatible("java.io.ObjectOutputStream")
459  private void writeObject(ObjectOutputStream stream) throws IOException {
460    stream.defaultWriteObject();
461    Serialization.writeMultimap(this, stream);
462  }
463
464  @GwtIncompatible("java.io.ObjectInputStream")
465  private void readObject(ObjectInputStream stream)
466      throws IOException, ClassNotFoundException {
467    stream.defaultReadObject();
468    int keyCount = stream.readInt();
469    if (keyCount < 0) {
470      throw new InvalidObjectException("Invalid key count " + keyCount);
471    }
472    ImmutableMap.Builder<Object, ImmutableSet<Object>> builder
473        = ImmutableMap.builder();
474    int tmpSize = 0;
475
476    for (int i = 0; i < keyCount; i++) {
477      Object key = stream.readObject();
478      int valueCount = stream.readInt();
479      if (valueCount <= 0) {
480        throw new InvalidObjectException("Invalid value count " + valueCount);
481      }
482
483      Object[] array = new Object[valueCount];
484      for (int j = 0; j < valueCount; j++) {
485        array[j] = stream.readObject();
486      }
487      ImmutableSet<Object> valueSet = ImmutableSet.copyOf(array);
488      if (valueSet.size() != array.length) {
489        throw new InvalidObjectException(
490            "Duplicate key-value pairs exist for key " + key);
491      }
492      builder.put(key, valueSet);
493      tmpSize += valueCount;
494    }
495
496    ImmutableMap<Object, ImmutableSet<Object>> tmpMap;
497    try {
498      tmpMap = builder.build();
499    } catch (IllegalArgumentException e) {
500      throw (InvalidObjectException)
501          new InvalidObjectException(e.getMessage()).initCause(e);
502    }
503
504    FieldSettersHolder.MAP_FIELD_SETTER.set(this, tmpMap);
505    FieldSettersHolder.SIZE_FIELD_SETTER.set(this, tmpSize);
506  }
507
508  @GwtIncompatible("not needed in emulated source.")
509  private static final long serialVersionUID = 0;
510}