Skip to content
Navigation Menu
{{ message }}
forked from xuebaobao526/JDK-Source-Code
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathConcurrentMap.java
More file actions
517 lines (499 loc) · 18.2 KB
/
Copy pathConcurrentMap.java
File metadata and controls
517 lines (499 loc) · 18.2 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
/*
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*/
/*
*
*
*
*
*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
* http://creativecommons.org/publicdomain/zero/1.0/
*/
package java.util.concurrent;
import java.util.Map;
import java.util.Objects;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Function;
/**
* A {@link java.util.Map} providing thread safety and atomicity
* guarantees.
*
* <p>Memory consistency effects: As with other concurrent
* collections, actions in a thread prior to placing an object into a
* {@code ConcurrentMap} as a key or value
* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
* actions subsequent to the access or removal of that object from
* the {@code ConcurrentMap} in another thread.
*
* <p>This interface is a member of the
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>.
*
* @since 1.5
* @author Doug Lea
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
*/
public interface ConcurrentMap<K, V> extends Map<K, V> {
/**
* {@inheritDoc}
*
* @implNote This implementation assumes that the ConcurrentMap cannot
* contain null values and {@code get()} returning null unambiguously means
* the key is absent. Implementations which support null values
* <strong>must</strong> override this default implementation.
*
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
default V getOrDefault(Object key, V defaultValue) {
V v;
return ((v = get(key)) != null) ? v : defaultValue;
}
/**
* {@inheritDoc}
*
* @implSpec The default implementation is equivalent to, for this
* {@code map}:
* <pre> {@code
* for ((Map.Entry<K, V> entry : map.entrySet())
* action.accept(entry.getKey(), entry.getValue());
* }</pre>
*
* @implNote The default implementation assumes that
* {@code IllegalStateException} thrown by {@code getKey()} or
* {@code getValue()} indicates that the entry has been removed and cannot
* be processed. Operation continues for subsequent entries.
*
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
default void forEach(BiConsumer<? super K, ? super V> action) {
Objects.requireNonNull(action);
for (Map.Entry<K, V> entry : entrySet()) {
K k;
V v;
try {
k = entry.getKey();
v = entry.getValue();
} catch(IllegalStateException ise) {
// this usually means the entry is no longer in the map.
continue;
}
action.accept(k, v);
}
}
/**
* If the specified key is not already associated
* with a value, associate it with the given value.
* This is equivalent to
* <pre> {@code
* if (!map.containsKey(key))
* return map.put(key, value);
* else
* return map.get(key);
* }</pre>
*
* except that the action is performed atomically.
*
* @implNote This implementation intentionally re-abstracts the
* inappropriate default provided in {@code Map}.
*
* @param key key with which the specified value is to be associated
* @param value value to be associated with the specified key
* @return the previous value associated with the specified key, or
* {@code null} if there was no mapping for the key.
* (A {@code null} return can also indicate that the map
* previously associated {@code null} with the key,
* if the implementation supports null values.)
* @throws UnsupportedOperationException if the {@code put} operation
* is not supported by this map
* @throws ClassCastException if the class of the specified key or value
* prevents it from being stored in this map
* @throws NullPointerException if the specified key or value is null,
* and this map does not permit null keys or values
* @throws IllegalArgumentException if some property of the specified key
* or value prevents it from being stored in this map
*/
V putIfAbsent(K key, V value);
/**
* Removes the entry for a key only if currently mapped to a given value.
* This is equivalent to
* <pre> {@code
* if (map.containsKey(key) && Objects.equals(map.get(key), value)) {
* map.remove(key);
* return true;
* } else
* return false;
* }</pre>
*
* except that the action is performed atomically.
*
* @implNote This implementation intentionally re-abstracts the
* inappropriate default provided in {@code Map}.
*
* @param key key with which the specified value is associated
* @param value value expected to be associated with the specified key
* @return {@code true} if the value was removed
* @throws UnsupportedOperationException if the {@code remove} operation
* is not supported by this map
* @throws ClassCastException if the key or value is of an inappropriate
* type for this map
* (<a href="../Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified key or value is null,
* and this map does not permit null keys or values
* (<a href="../Collection.html#optional-restrictions">optional</a>)
*/
boolean remove(Object key, Object value);
/**
* Replaces the entry for a key only if currently mapped to a given value.
* This is equivalent to
* <pre> {@code
* if (map.containsKey(key) && Objects.equals(map.get(key), oldValue)) {
* map.put(key, newValue);
* return true;
* } else
* return false;
* }</pre>
*
* except that the action is performed atomically.
*
* @implNote This implementation intentionally re-abstracts the
* inappropriate default provided in {@code Map}.
*
* @param key key with which the specified value is associated
* @param oldValue value expected to be associated with the specified key
* @param newValue value to be associated with the specified key
* @return {@code true} if the value was replaced
* @throws UnsupportedOperationException if the {@code put} operation
* is not supported by this map
* @throws ClassCastException if the class of a specified key or value
* prevents it from being stored in this map
* @throws NullPointerException if a specified key or value is null,
* and this map does not permit null keys or values
* @throws IllegalArgumentException if some property of a specified key
* or value prevents it from being stored in this map
*/
boolean replace(K key, V oldValue, V newValue);
/**
* Replaces the entry for a key only if currently mapped to some value.
* This is equivalent to
* <pre> {@code
* if (map.containsKey(key)) {
* return map.put(key, value);
* } else
* return null;
* }</pre>
*
* except that the action is performed atomically.
*
* @implNote This implementation intentionally re-abstracts the
* inappropriate default provided in {@code Map}.
*
* @param key key with which the specified value is associated
* @param value value to be associated with the specified key
* @return the previous value associated with the specified key, or
* {@code null} if there was no mapping for the key.
* (A {@code null} return can also indicate that the map
* previously associated {@code null} with the key,
* if the implementation supports null values.)
* @throws UnsupportedOperationException if the {@code put} operation
* is not supported by this map
* @throws ClassCastException if the class of the specified key or value
* prevents it from being stored in this map
* @throws NullPointerException if the specified key or value is null,
* and this map does not permit null keys or values
* @throws IllegalArgumentException if some property of the specified key
* or value prevents it from being stored in this map
*/
V replace(K key, V value);
/**
* {@inheritDoc}
*
* @implSpec
* <p>The default implementation is equivalent to, for this {@code map}:
* <pre> {@code
* for ((Map.Entry<K, V> entry : map.entrySet())
* do {
* K k = entry.getKey();
* V v = entry.getValue();
* } while(!replace(k, v, function.apply(k, v)));
* }</pre>
*
* The default implementation may retry these steps when multiple
* threads attempt updates including potentially calling the function
* repeatedly for a given key.
*
* <p>This implementation assumes that the ConcurrentMap cannot contain null
* values and {@code get()} returning null unambiguously means the key is
* absent. Implementations which support null values <strong>must</strong>
* override this default implementation.
*
* @throws UnsupportedOperationException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
* @since 1.8
*/
@Override
default void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
Objects.requireNonNull(function);
forEach((k,v) -> {
while(!replace(k, v, function.apply(k, v))) {
// v changed or k is gone
if ( (v = get(k)) == null) {
// k is no longer in the map.
break;
}
}
});
}
/**
* {@inheritDoc}
*
* @implSpec
* The default implementation is equivalent to the following steps for this
* {@code map}, then returning the current value or {@code null} if now
* absent:
*
* <pre> {@code
* if (map.get(key) == null) {
* V newValue = mappingFunction.apply(key);
* if (newValue != null)
* return map.putIfAbsent(key, newValue);
* }
* }</pre>
*
* The default implementation may retry these steps when multiple
* threads attempt updates including potentially calling the mapping
* function multiple times.
*
* <p>This implementation assumes that the ConcurrentMap cannot contain null
* values and {@code get()} returning null unambiguously means the key is
* absent. Implementations which support null values <strong>must</strong>
* override this default implementation.
*
* @throws UnsupportedOperationException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
default V computeIfAbsent(K key,
Function<? super K, ? extends V> mappingFunction) {
Objects.requireNonNull(mappingFunction);
V v, newValue;
return ((v = get(key)) == null &&
(newValue = mappingFunction.apply(key)) != null &&
(v = putIfAbsent(key, newValue)) == null) ? newValue : v;
}
/**
* {@inheritDoc}
*
* @implSpec
* The default implementation is equivalent to performing the following
* steps for this {@code map}, then returning the current value or
* {@code null} if now absent. :
*
* <pre> {@code
* if (map.get(key) != null) {
* V oldValue = map.get(key);
* V newValue = remappingFunction.apply(key, oldValue);
* if (newValue != null)
* map.replace(key, oldValue, newValue);
* else
* map.remove(key, oldValue);
* }
* }</pre>
*
* The default implementation may retry these steps when multiple threads
* attempt updates including potentially calling the remapping function
* multiple times.
*
* <p>This implementation assumes that the ConcurrentMap cannot contain null
* values and {@code get()} returning null unambiguously means the key is
* absent. Implementations which support null values <strong>must</strong>
* override this default implementation.
*
* @throws UnsupportedOperationException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
default V computeIfPresent(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
Objects.requireNonNull(remappingFunction);
V oldValue;
while((oldValue = get(key)) != null) {
V newValue = remappingFunction.apply(key, oldValue);
if (newValue != null) {
if (replace(key, oldValue, newValue))
return newValue;
} else if (remove(key, oldValue))
return null;
}
return oldValue;
}
/**
* {@inheritDoc}
*
* @implSpec
* The default implementation is equivalent to performing the following
* steps for this {@code map}, then returning the current value or
* {@code null} if absent:
*
* <pre> {@code
* V oldValue = map.get(key);
* V newValue = remappingFunction.apply(key, oldValue);
* if (oldValue != null ) {
* if (newValue != null)
* map.replace(key, oldValue, newValue);
* else
* map.remove(key, oldValue);
* } else {
* if (newValue != null)
* map.putIfAbsent(key, newValue);
* else
* return null;
* }
* }</pre>
*
* The default implementation may retry these steps when multiple
* threads attempt updates including potentially calling the remapping
* function multiple times.
*
* <p>This implementation assumes that the ConcurrentMap cannot contain null
* values and {@code get()} returning null unambiguously means the key is
* absent. Implementations which support null values <strong>must</strong>
* override this default implementation.
*
* @throws UnsupportedOperationException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
default V compute(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
Objects.requireNonNull(remappingFunction);
V oldValue = get(key);
for(;;) {
V newValue = remappingFunction.apply(key, oldValue);
if (newValue == null) {
// delete mapping
if (oldValue != null || containsKey(key)) {
// something to remove
if (remove(key, oldValue)) {
// removed the old value as expected
return null;
}
// some other value replaced old value. try again.
oldValue = get(key);
} else {
// nothing to do. Leave things as they were.
return null;
}
} else {
// add or replace old mapping
if (oldValue != null) {
// replace
if (replace(key, oldValue, newValue)) {
// replaced as expected.
return newValue;
}
// some other value replaced old value. try again.
oldValue = get(key);
} else {
// add (replace if oldValue was null)
if ((oldValue = putIfAbsent(key, newValue)) == null) {
// replaced
return newValue;
}
// some other value replaced old value. try again.
}
}
}
}
/**
* {@inheritDoc}
*
* @implSpec
* The default implementation is equivalent to performing the following
* steps for this {@code map}, then returning the current value or
* {@code null} if absent:
*
* <pre> {@code
* V oldValue = map.get(key);
* V newValue = (oldValue == null) ? value :
* remappingFunction.apply(oldValue, value);
* if (newValue == null)
* map.remove(key);
* else
* map.put(key, newValue);
* }</pre>
*
* <p>The default implementation may retry these steps when multiple
* threads attempt updates including potentially calling the remapping
* function multiple times.
*
* <p>This implementation assumes that the ConcurrentMap cannot contain null
* values and {@code get()} returning null unambiguously means the key is
* absent. Implementations which support null values <strong>must</strong>
* override this default implementation.
*
* @throws UnsupportedOperationException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
default V merge(K key, V value,
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
Objects.requireNonNull(remappingFunction);
Objects.requireNonNull(value);
V oldValue = get(key);
for (;;) {
if (oldValue != null) {
V newValue = remappingFunction.apply(oldValue, value);
if (newValue != null) {
if (replace(key, oldValue, newValue))
return newValue;
} else if (remove(key, oldValue)) {
return null;
}
oldValue = get(key);
} else {
if ((oldValue = putIfAbsent(key, value)) == null) {
return value;
}
}
}
}
}
You can’t perform that action at this time.