1 /*
2 * Copyright (C) 2008 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
17 package com.google.common.collect;
18
19 import static com.google.common.base.Preconditions.checkState;
20 import static com.google.common.collect.CollectPreconditions.checkNonnegative;
21
22 import com.google.common.annotations.Beta;
23 import com.google.common.annotations.GwtCompatible;
24 import com.google.common.annotations.VisibleForTesting;
25 import com.google.errorprone.annotations.CanIgnoreReturnValue;
26 import com.google.errorprone.annotations.DoNotCall;
27 import java.util.Arrays;
28 import java.util.Comparator;
29 import java.util.Map;
30 import java.util.function.Function;
31 import java.util.stream.Collector;
32 import java.util.stream.Collectors;
33
34 /**
35 * A {@link BiMap} whose contents will never change, with many other important properties detailed
36 * at {@link ImmutableCollection}.
37 *
38 * @author Jared Levy
39 * @since 2.0
40 */
41 @GwtCompatible(serializable = true, emulated = true)
42 public abstract class ImmutableBiMap<K, V> extends ImmutableBiMapFauxverideShim<K, V>
43 implements BiMap<K, V> {
44
45 /**
46 * Returns a {@link Collector} that accumulates elements into an {@code ImmutableBiMap} whose keys
47 * and values are the result of applying the provided mapping functions to the input elements.
48 * Entries appear in the result {@code ImmutableBiMap} in encounter order.
49 *
50 * <p>If the mapped keys or values contain duplicates (according to {@link Object#equals(Object)},
51 * an {@code IllegalArgumentException} is thrown when the collection operation is performed. (This
52 * differs from the {@code Collector} returned by {@link Collectors#toMap(Function, Function)},
53 * which throws an {@code IllegalStateException}.)
54 *
55 * @since 21.0
56 */
57 public static <T, K, V> Collector<T, ?, ImmutableBiMap<K, V>> toImmutableBiMap(
58 Function<? super T, ? extends K> keyFunction,
59 Function<? super T, ? extends V> valueFunction) {
60 return CollectCollectors.toImmutableBiMap(keyFunction, valueFunction);
61 }
62
63 /**
64 * Returns the empty bimap.
65 *
66 * <p><b>Performance note:</b> the instance returned is a singleton.
67 */
68 // Casting to any type is safe because the set will never hold any elements.
69 @SuppressWarnings("unchecked")
70 public static <K, V> ImmutableBiMap<K, V> of() {
71 return (ImmutableBiMap<K, V>) RegularImmutableBiMap.EMPTY;
72 }
73
74 /** Returns an immutable bimap containing a single entry. */
75 public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1) {
76 return new SingletonImmutableBiMap<>(k1, v1);
77 }
78
79 /**
80 * Returns an immutable map containing the given entries, in order.
81 *
82 * @throws IllegalArgumentException if duplicate keys or values are added
83 */
84 public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2) {
85 return RegularImmutableBiMap.fromEntries(entryOf(k1, v1), entryOf(k2, v2));
86 }
87
88 /**
89 * Returns an immutable map containing the given entries, in order.
90 *
91 * @throws IllegalArgumentException if duplicate keys or values are added
92 */
93 public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
94 return RegularImmutableBiMap.fromEntries(entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3));
95 }
96
97 /**
98 * Returns an immutable map containing the given entries, in order.
99 *
100 * @throws IllegalArgumentException if duplicate keys or values are added
101 */
102 public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
103 return RegularImmutableBiMap.fromEntries(
104 entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3), entryOf(k4, v4));
105 }
106
107 /**
108 * Returns an immutable map containing the given entries, in order.
109 *
110 * @throws IllegalArgumentException if duplicate keys or values are added
111 */
112 public static <K, V> ImmutableBiMap<K, V> of(
113 K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
114 return RegularImmutableBiMap.fromEntries(
115 entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3), entryOf(k4, v4), entryOf(k5, v5));
116 }
117
118 // looking for of() with > 5 entries? Use the builder instead.
119
120 /**
121 * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
122 * Builder} constructor.
123 */
124 public static <K, V> Builder<K, V> builder() {
125 return new Builder<>();
126 }
127
128 /**
129 * Returns a new builder, expecting the specified number of entries to be added.
130 *
131 * <p>If {@code expectedSize} is exactly the number of entries added to the builder before {@link
132 * Builder#build} is called, the builder is likely to perform better than an unsized {@link
133 * #builder()} would have.
134 *
135 * <p>It is not specified if any performance benefits apply if {@code expectedSize} is close to,
136 * but not exactly, the number of entries added to the builder.
137 *
138 * @since 23.1
139 */
140 @Beta
141 public static <K, V> Builder<K, V> builderWithExpectedSize(int expectedSize) {
142 checkNonnegative(expectedSize, "expectedSize");
143 return new Builder<>(expectedSize);
144 }
145
146 /**
147 * A builder for creating immutable bimap instances, especially {@code public static final} bimaps
148 * ("constant bimaps"). Example:
149 *
150 * <pre>{@code
151 * static final ImmutableBiMap<String, Integer> WORD_TO_INT =
152 * new ImmutableBiMap.Builder<String, Integer>()
153 * .put("one", 1)
154 * .put("two", 2)
155 * .put("three", 3)
156 * .build();
157 * }</pre>
158 *
159 * <p>For <i>small</i> immutable bimaps, the {@code ImmutableBiMap.of()} methods are even more
160 * convenient.
161 *
162 * <p>By default, a {@code Builder} will generate bimaps that iterate over entries in the order
163 * they were inserted into the builder. For example, in the above example, {@code
164 * WORD_TO_INT.entrySet()} is guaranteed to iterate over the entries in the order {@code "one"=1,
165 * "two"=2, "three"=3}, and {@code keySet()} and {@code values()} respect the same order. If you
166 * want a different order, consider using {@link #orderEntriesByValue(Comparator)}, which changes
167 * this builder to sort entries by value.
168 *
169 * <p>Builder instances can be reused - it is safe to call {@link #build} multiple times to build
170 * multiple bimaps in series. Each bimap is a superset of the bimaps created before it.
171 *
172 * @since 2.0
173 */
174 public static final class Builder<K, V> extends ImmutableMap.Builder<K, V> {
175
176 /**
177 * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
178 * ImmutableBiMap#builder}.
179 */
180 public Builder() {}
181
182 Builder(int size) {
183 super(size);
184 }
185
186 /**
187 * Associates {@code key} with {@code value} in the built bimap. Duplicate keys or values are
188 * not allowed, and will cause {@link #build} to fail.
189 */
190 @CanIgnoreReturnValue
191 @Override
192 public Builder<K, V> put(K key, V value) {
193 super.put(key, value);
194 return this;
195 }
196
197 /**
198 * Adds the given {@code entry} to the bimap. Duplicate keys or values are not allowed, and will
199 * cause {@link #build} to fail.
200 *
201 * @since 19.0
202 */
203 @CanIgnoreReturnValue
204 @Override
205 public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
206 super.put(entry);
207 return this;
208 }
209
210 /**
211 * Associates all of the given map's keys and values in the built bimap. Duplicate keys or
212 * values are not allowed, and will cause {@link #build} to fail.
213 *
214 * @throws NullPointerException if any key or value in {@code map} is null
215 */
216 @CanIgnoreReturnValue
217 @Override
218 public Builder<K, V> putAll(Map<? extends K, ? extends V> map) {
219 super.putAll(map);
220 return this;
221 }
222
223 /**
224 * Adds all of the given entries to the built bimap. Duplicate keys or values are not allowed,
225 * and will cause {@link #build} to fail.
226 *
227 * @throws NullPointerException if any key, value, or entry is null
228 * @since 19.0
229 */
230 @CanIgnoreReturnValue
231 @Beta
232 @Override
233 public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries) {
234 super.putAll(entries);
235 return this;
236 }
237
238 /**
239 * Configures this {@code Builder} to order entries by value according to the specified
240 * comparator.
241 *
242 * <p>The sort order is stable, that is, if two entries have values that compare as equivalent,
243 * the entry that was inserted first will be first in the built map's iteration order.
244 *
245 * @throws IllegalStateException if this method was already called
246 * @since 19.0
247 */
248 @CanIgnoreReturnValue
249 @Beta
250 @Override
251 public Builder<K, V> orderEntriesByValue(Comparator<? super V> valueComparator) {
252 super.orderEntriesByValue(valueComparator);
253 return this;
254 }
255
256 @Override
257 @CanIgnoreReturnValue
258 Builder<K, V> combine(ImmutableMap.Builder<K, V> builder) {
259 super.combine(builder);
260 return this;
261 }
262
263 /**
264 * Returns a newly-created immutable bimap. The iteration order of the returned bimap is the
265 * order in which entries were inserted into the builder, unless {@link #orderEntriesByValue}
266 * was called, in which case entries are sorted by value.
267 *
268 * @throws IllegalArgumentException if duplicate keys or values were added
269 */
270 @Override
271 public ImmutableBiMap<K, V> build() {
272 switch (size) {
273 case 0:
274 return of();
275 case 1:
276 return of(entries[0].getKey(), entries[0].getValue());
277 default:
278 /*
279 * If entries is full, or if hash flooding is detected, then this implementation may end
280 * up using the entries array directly and writing over the entry objects with
281 * non-terminal entries, but this is safe; if this Builder is used further, it will grow
282 * the entries array (so it can't affect the original array), and future build() calls
283 * will always copy any entry objects that cannot be safely reused.
284 */
285 if (valueComparator != null) {
286 if (entriesUsed) {
287 entries = Arrays.copyOf(entries, size);
288 }
289 Arrays.sort(
290 entries,
291 0,
292 size,
293 Ordering.from(valueComparator).onResultOf(Maps.<V>valueFunction()));
294 }
295 entriesUsed = true;
296 return RegularImmutableBiMap.fromEntryArray(size, entries);
297 }
298 }
299
300 @Override
301 @VisibleForTesting
302 ImmutableBiMap<K, V> buildJdkBacked() {
303 checkState(
304 valueComparator == null,
305 "buildJdkBacked is for tests only, doesn't support orderEntriesByValue");
306 switch (size) {
307 case 0:
308 return of();
309 case 1:
310 return of(entries[0].getKey(), entries[0].getValue());
311 default:
312 entriesUsed = true;
313 return RegularImmutableBiMap.fromEntryArray(size, entries);
314 }
315 }
316 }
317
318 /**
319 * Returns an immutable bimap containing the same entries as {@code map}. If {@code map} somehow
320 * contains entries with duplicate keys (for example, if it is a {@code SortedMap} whose
321 * comparator is not <i>consistent with equals</i>), the results of this method are undefined.
322 *
323 * <p>The returned {@code BiMap} iterates over entries in the same order as the {@code entrySet}
324 * of the original map.
325 *
326 * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
327 * safe to do so. The exact circumstances under which a copy will or will not be performed are
328 * undocumented and subject to change.
329 *
330 * @throws IllegalArgumentException if two keys have the same value or two values have the same
331 * key
332 * @throws NullPointerException if any key or value in {@code map} is null
333 */
334 public static <K, V> ImmutableBiMap<K, V> copyOf(Map<? extends K, ? extends V> map) {
335 if (map instanceof ImmutableBiMap) {
336 @SuppressWarnings("unchecked") // safe since map is not writable
337 ImmutableBiMap<K, V> bimap = (ImmutableBiMap<K, V>) map;
338 // TODO(lowasser): if we need to make a copy of a BiMap because the
339 // forward map is a view, don't make a copy of the non-view delegate map
340 if (!bimap.isPartialView()) {
341 return bimap;
342 }
343 }
344 return copyOf(map.entrySet());
345 }
346
347 /**
348 * Returns an immutable bimap containing the given entries. The returned bimap iterates over
349 * entries in the same order as the original iterable.
350 *
351 * @throws IllegalArgumentException if two keys have the same value or two values have the same
352 * key
353 * @throws NullPointerException if any key, value, or entry is null
354 * @since 19.0
355 */
356 @Beta
357 public static <K, V> ImmutableBiMap<K, V> copyOf(
358 Iterable<? extends Entry<? extends K, ? extends V>> entries) {
359 @SuppressWarnings("unchecked") // we'll only be using getKey and getValue, which are covariant
360 Entry<K, V>[] entryArray = (Entry<K, V>[]) Iterables.toArray(entries, EMPTY_ENTRY_ARRAY);
361 switch (entryArray.length) {
362 case 0:
363 return of();
364 case 1:
365 Entry<K, V> entry = entryArray[0];
366 return of(entry.getKey(), entry.getValue());
367 default:
368 /*
369 * The current implementation will end up using entryArray directly, though it will write
370 * over the (arbitrary, potentially mutable) Entry objects actually stored in entryArray.
371 */
372 return RegularImmutableBiMap.fromEntries(entryArray);
373 }
374 }
375
376 ImmutableBiMap() {}
377
378 /**
379 * {@inheritDoc}
380 *
381 * <p>The inverse of an {@code ImmutableBiMap} is another {@code ImmutableBiMap}.
382 */
383 @Override
384 public abstract ImmutableBiMap<V, K> inverse();
385
386 /**
387 * Returns an immutable set of the values in this map, in the same order they appear in {@link
388 * #entrySet}.
389 */
390 @Override
391 public ImmutableSet<V> values() {
392 return inverse().keySet();
393 }
394
395 @Override
396 final ImmutableSet<V> createValues() {
397 throw new AssertionError("should never be called");
398 }
399
400 /**
401 * Guaranteed to throw an exception and leave the bimap unmodified.
402 *
403 * @throws UnsupportedOperationException always
404 * @deprecated Unsupported operation.
405 */
406 @CanIgnoreReturnValue
407 @Deprecated
408 @Override
409 @DoNotCall("Always throws UnsupportedOperationException")
410 public final V forcePut(K key, V value) {
411 throw new UnsupportedOperationException();
412 }
413
414 /**
415 * Serialized type for all ImmutableBiMap instances. It captures the logical contents and they are
416 * reconstructed using public factory methods. This ensures that the implementation types remain
417 * as implementation details.
418 *
419 * <p>Since the bimap is immutable, ImmutableBiMap doesn't require special logic for keeping the
420 * bimap and its inverse in sync during serialization, the way AbstractBiMap does.
421 */
422 private static class SerializedForm<K, V> extends ImmutableMap.SerializedForm<K, V> {
423 SerializedForm(ImmutableBiMap<K, V> bimap) {
424 super(bimap);
425 }
426
427 @Override
428 Builder<K, V> makeBuilder(int size) {
429 return new Builder<>(size);
430 }
431
432 private static final long serialVersionUID = 0;
433 }
434
435 @Override
436 Object writeReplace() {
437 return new SerializedForm<>(this);
438 }
439 }