1 |
dl |
1.2 |
/* |
2 |
|
|
* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
dl |
1.17 |
* Expert Group and released to the public domain, as explained at |
4 |
jsr166 |
1.31 |
* http://creativecommons.org/publicdomain/zero/1.0/ |
5 |
dl |
1.2 |
*/ |
6 |
|
|
|
7 |
tim |
1.1 |
package java.util.concurrent; |
8 |
|
|
import java.util.Map; |
9 |
dl |
1.46 |
import java.util.Objects; |
10 |
|
|
import java.util.function.BiConsumer; |
11 |
dl |
1.44 |
import java.util.function.BiFunction; |
12 |
dl |
1.46 |
import java.util.function.Function; |
13 |
tim |
1.1 |
|
14 |
|
|
/** |
15 |
jsr166 |
1.43 |
* A {@link java.util.Map} providing thread safety and atomicity |
16 |
dl |
1.42 |
* guarantees. |
17 |
dl |
1.19 |
* |
18 |
dl |
1.46 |
* <p>To support atomic usages, ConcurrentMaps are expected not to |
19 |
|
|
* allow {@code null} as a legal value (and to throw exceptions upon |
20 |
|
|
* attempted insertions). This enables a return value of {@code null} |
21 |
|
|
* to unambiguously indicate the absence of a mapping. This interface |
22 |
|
|
* does not strictly forbid implementations that may hold {@code null} |
23 |
|
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* values. However, in any that do so, a {@code null} value must bear |
24 |
|
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* the same interpretation as the absence of a mapping in order to |
25 |
|
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* conform to method atomicity requirements. Further, any that do so |
26 |
|
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* must override all default method implementations. |
27 |
|
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* |
28 |
|
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* <p>Several methods (for example {@link #putIfAbsent}) inherited |
29 |
|
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* from {@link Map} do not have default implementations, and so must |
30 |
|
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* be provided by implementations of this interface, even though they |
31 |
|
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* have (non-atomic) default implementations in the {@link Map} |
32 |
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* interface. |
33 |
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* |
34 |
jsr166 |
1.29 |
* <p>Memory consistency effects: As with other concurrent |
35 |
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* collections, actions in a thread prior to placing an object into a |
36 |
|
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* {@code ConcurrentMap} as a key or value |
37 |
|
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* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> |
38 |
|
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* actions subsequent to the access or removal of that object from |
39 |
|
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* the {@code ConcurrentMap} in another thread. |
40 |
|
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* |
41 |
dl |
1.19 |
* <p>This interface is a member of the |
42 |
jsr166 |
1.30 |
* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
43 |
jsr166 |
1.47 |
* Java Collections Framework</a>. |
44 |
jsr166 |
1.21 |
* |
45 |
dl |
1.4 |
* @since 1.5 |
46 |
|
|
* @author Doug Lea |
47 |
dl |
1.13 |
* @param <K> the type of keys maintained by this map |
48 |
jsr166 |
1.21 |
* @param <V> the type of mapped values |
49 |
dl |
1.4 |
*/ |
50 |
jsr166 |
1.47 |
public interface ConcurrentMap<K,V> extends Map<K,V> { |
51 |
dl |
1.41 |
|
52 |
|
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/** |
53 |
|
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* {@inheritDoc} |
54 |
|
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* |
55 |
dl |
1.46 |
* @implNote The default implementation returns the result of |
56 |
|
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* {@code get(key)} unless {@code null}, in which case it returns |
57 |
|
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* the given defaultValue. |
58 |
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* |
59 |
|
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* @throws ClassCastException {@inheritDoc} |
60 |
|
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* @throws NullPointerException {@inheritDoc} |
61 |
|
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* @since 1.8 |
62 |
dl |
1.41 |
*/ |
63 |
|
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@Override |
64 |
|
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default V getOrDefault(Object key, V defaultValue) { |
65 |
|
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V v; |
66 |
|
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return ((v = get(key)) != null) ? v : defaultValue; |
67 |
|
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} |
68 |
|
|
|
69 |
dl |
1.46 |
/** |
70 |
|
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* {@inheritDoc} |
71 |
|
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* |
72 |
|
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* @implSpec The default implementation is equivalent to, for this |
73 |
|
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* {@code map}: |
74 |
|
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* <pre> {@code |
75 |
jsr166 |
1.49 |
* for (Map.Entry<K,V> entry : map.entrySet()) |
76 |
jsr166 |
1.48 |
* action.accept(entry.getKey(), entry.getValue()); |
77 |
dl |
1.46 |
* }</pre> |
78 |
|
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* |
79 |
|
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* @implNote The default implementation assumes that {@code |
80 |
|
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* IllegalStateException} thrown by {@code getKey()} or {@code |
81 |
|
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* getValue()} indicates that the entry no longer exists. |
82 |
|
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* Operation continues for subsequent entries. |
83 |
|
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* |
84 |
|
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* @throws NullPointerException {@inheritDoc} |
85 |
|
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* @since 1.8 |
86 |
|
|
*/ |
87 |
|
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@Override |
88 |
|
|
default void forEach(BiConsumer<? super K, ? super V> action) { |
89 |
|
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Objects.requireNonNull(action); |
90 |
jsr166 |
1.47 |
for (Map.Entry<K,V> entry : entrySet()) { |
91 |
dl |
1.46 |
K k; |
92 |
|
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V v; |
93 |
|
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try { |
94 |
|
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k = entry.getKey(); |
95 |
|
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v = entry.getValue(); |
96 |
jsr166 |
1.47 |
} catch (IllegalStateException ise) { |
97 |
dl |
1.46 |
// this usually means the entry is no longer in the map. |
98 |
|
|
continue; |
99 |
|
|
} |
100 |
|
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action.accept(k, v); |
101 |
|
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} |
102 |
|
|
} |
103 |
|
|
|
104 |
tim |
1.1 |
/** |
105 |
|
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* If the specified key is not already associated |
106 |
dl |
1.46 |
* with a value, associates it with the given value. |
107 |
tim |
1.1 |
* This is equivalent to |
108 |
jsr166 |
1.36 |
* <pre> {@code |
109 |
jsr166 |
1.48 |
* if (map.containsKey(key)) |
110 |
|
|
* return map.get(key); |
111 |
|
|
* else |
112 |
jsr166 |
1.36 |
* return map.put(key, value); |
113 |
dl |
1.46 |
* }</pre> |
114 |
jsr166 |
1.36 |
* |
115 |
jsr166 |
1.21 |
* except that the action is performed atomically. |
116 |
|
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* |
117 |
dl |
1.46 |
* @implNote There is no default implementation. |
118 |
|
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* |
119 |
jsr166 |
1.24 |
* @param key key with which the specified value is to be associated |
120 |
|
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* @param value value to be associated with the specified key |
121 |
jsr166 |
1.25 |
* @return the previous value associated with the specified key, or |
122 |
jsr166 |
1.38 |
* {@code null} if there was no mapping for the key. |
123 |
|
|
* (A {@code null} return can also indicate that the map |
124 |
|
|
* previously associated {@code null} with the key, |
125 |
jsr166 |
1.25 |
* if the implementation supports null values.) |
126 |
jsr166 |
1.38 |
* @throws UnsupportedOperationException if the {@code put} operation |
127 |
jsr166 |
1.24 |
* is not supported by this map |
128 |
tim |
1.1 |
* @throws ClassCastException if the class of the specified key or value |
129 |
jsr166 |
1.24 |
* prevents it from being stored in this map |
130 |
|
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* @throws NullPointerException if the specified key or value is null, |
131 |
|
|
* and this map does not permit null keys or values |
132 |
|
|
* @throws IllegalArgumentException if some property of the specified key |
133 |
|
|
* or value prevents it from being stored in this map |
134 |
dl |
1.18 |
*/ |
135 |
jsr166 |
1.47 |
V putIfAbsent(K key, V value); |
136 |
dl |
1.6 |
|
137 |
|
|
/** |
138 |
jsr166 |
1.21 |
* Removes the entry for a key only if currently mapped to a given value. |
139 |
|
|
* This is equivalent to |
140 |
jsr166 |
1.36 |
* <pre> {@code |
141 |
dl |
1.40 |
* if (map.containsKey(key) && Objects.equals(map.get(key), value)) { |
142 |
jsr166 |
1.36 |
* map.remove(key); |
143 |
|
|
* return true; |
144 |
|
|
* } else |
145 |
dl |
1.46 |
* return false; |
146 |
|
|
* }</pre> |
147 |
jsr166 |
1.36 |
* |
148 |
dl |
1.6 |
* except that the action is performed atomically. |
149 |
jsr166 |
1.21 |
* |
150 |
dl |
1.46 |
* @implNote There is no default implementation. |
151 |
|
|
* |
152 |
jsr166 |
1.24 |
* @param key key with which the specified value is associated |
153 |
jsr166 |
1.25 |
* @param value value expected to be associated with the specified key |
154 |
jsr166 |
1.38 |
* @return {@code true} if the value was removed |
155 |
|
|
* @throws UnsupportedOperationException if the {@code remove} operation |
156 |
jsr166 |
1.24 |
* is not supported by this map |
157 |
jsr166 |
1.25 |
* @throws ClassCastException if the key or value is of an inappropriate |
158 |
jsr166 |
1.35 |
* type for this map |
159 |
dl |
1.33 |
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
160 |
jsr166 |
1.24 |
* @throws NullPointerException if the specified key or value is null, |
161 |
dl |
1.32 |
* and this map does not permit null keys or values |
162 |
dl |
1.33 |
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
163 |
dl |
1.6 |
*/ |
164 |
dl |
1.7 |
boolean remove(Object key, Object value); |
165 |
dl |
1.14 |
|
166 |
|
|
/** |
167 |
jsr166 |
1.21 |
* Replaces the entry for a key only if currently mapped to a given value. |
168 |
|
|
* This is equivalent to |
169 |
jsr166 |
1.36 |
* <pre> {@code |
170 |
dl |
1.40 |
* if (map.containsKey(key) && Objects.equals(map.get(key), oldValue)) { |
171 |
jsr166 |
1.36 |
* map.put(key, newValue); |
172 |
|
|
* return true; |
173 |
|
|
* } else |
174 |
dl |
1.46 |
* return false; |
175 |
|
|
* }</pre> |
176 |
jsr166 |
1.36 |
* |
177 |
dl |
1.14 |
* except that the action is performed atomically. |
178 |
jsr166 |
1.21 |
* |
179 |
dl |
1.46 |
* @implNote There is no default implementation. |
180 |
|
|
* |
181 |
jsr166 |
1.24 |
* @param key key with which the specified value is associated |
182 |
|
|
* @param oldValue value expected to be associated with the specified key |
183 |
|
|
* @param newValue value to be associated with the specified key |
184 |
jsr166 |
1.38 |
* @return {@code true} if the value was replaced |
185 |
|
|
* @throws UnsupportedOperationException if the {@code put} operation |
186 |
jsr166 |
1.24 |
* is not supported by this map |
187 |
jsr166 |
1.25 |
* @throws ClassCastException if the class of a specified key or value |
188 |
|
|
* prevents it from being stored in this map |
189 |
jsr166 |
1.24 |
* @throws NullPointerException if a specified key or value is null, |
190 |
|
|
* and this map does not permit null keys or values |
191 |
jsr166 |
1.25 |
* @throws IllegalArgumentException if some property of a specified key |
192 |
|
|
* or value prevents it from being stored in this map |
193 |
dl |
1.14 |
*/ |
194 |
|
|
boolean replace(K key, V oldValue, V newValue); |
195 |
dl |
1.6 |
|
196 |
dl |
1.15 |
/** |
197 |
jsr166 |
1.21 |
* Replaces the entry for a key only if currently mapped to some value. |
198 |
|
|
* This is equivalent to |
199 |
jsr166 |
1.36 |
* <pre> {@code |
200 |
|
|
* if (map.containsKey(key)) { |
201 |
|
|
* return map.put(key, value); |
202 |
|
|
* } else |
203 |
dl |
1.46 |
* return null; |
204 |
|
|
* }</pre> |
205 |
jsr166 |
1.36 |
* |
206 |
dl |
1.15 |
* except that the action is performed atomically. |
207 |
jsr166 |
1.21 |
* |
208 |
dl |
1.46 |
* @implNote There is no default implementation. |
209 |
|
|
* |
210 |
jsr166 |
1.24 |
* @param key key with which the specified value is associated |
211 |
|
|
* @param value value to be associated with the specified key |
212 |
jsr166 |
1.25 |
* @return the previous value associated with the specified key, or |
213 |
jsr166 |
1.38 |
* {@code null} if there was no mapping for the key. |
214 |
|
|
* (A {@code null} return can also indicate that the map |
215 |
|
|
* previously associated {@code null} with the key, |
216 |
jsr166 |
1.25 |
* if the implementation supports null values.) |
217 |
jsr166 |
1.38 |
* @throws UnsupportedOperationException if the {@code put} operation |
218 |
jsr166 |
1.24 |
* is not supported by this map |
219 |
jsr166 |
1.25 |
* @throws ClassCastException if the class of the specified key or value |
220 |
|
|
* prevents it from being stored in this map |
221 |
jsr166 |
1.24 |
* @throws NullPointerException if the specified key or value is null, |
222 |
|
|
* and this map does not permit null keys or values |
223 |
jsr166 |
1.25 |
* @throws IllegalArgumentException if some property of the specified key |
224 |
|
|
* or value prevents it from being stored in this map |
225 |
dl |
1.15 |
*/ |
226 |
dl |
1.16 |
V replace(K key, V value); |
227 |
dl |
1.44 |
|
228 |
|
|
/** |
229 |
|
|
* {@inheritDoc} |
230 |
|
|
* |
231 |
dl |
1.46 |
* @implSpec |
232 |
|
|
* <p>The default implementation is equivalent to, for this {@code map}: |
233 |
|
|
* <pre> {@code |
234 |
jsr166 |
1.49 |
* for (Map.Entry<K,V> entry : map.entrySet()) |
235 |
dl |
1.46 |
* do { |
236 |
|
|
* K k = entry.getKey(); |
237 |
|
|
* V v = entry.getValue(); |
238 |
jsr166 |
1.47 |
* } while (!replace(k, v, function.apply(k, v))); |
239 |
dl |
1.46 |
* }</pre> |
240 |
|
|
* |
241 |
|
|
* The default implementation may retry these steps when multiple |
242 |
|
|
* threads attempt updates, and may call the function multiple |
243 |
|
|
* times. |
244 |
|
|
* |
245 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
246 |
|
|
* @throws NullPointerException {@inheritDoc} |
247 |
|
|
* @throws ClassCastException {@inheritDoc} |
248 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
249 |
|
|
* @since 1.8 |
250 |
dl |
1.44 |
*/ |
251 |
|
|
@Override |
252 |
|
|
default void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { |
253 |
dl |
1.46 |
Objects.requireNonNull(function); |
254 |
|
|
forEach((k,v) -> { |
255 |
jsr166 |
1.47 |
while (!replace(k, v, function.apply(k, v))) { |
256 |
dl |
1.46 |
// v changed or k is gone |
257 |
|
|
if ( (v = get(k)) == null) { |
258 |
|
|
// k is no longer in the map. |
259 |
|
|
break; |
260 |
|
|
} |
261 |
dl |
1.44 |
} |
262 |
dl |
1.46 |
}); |
263 |
|
|
} |
264 |
|
|
|
265 |
|
|
/** |
266 |
|
|
* {@inheritDoc} |
267 |
|
|
* |
268 |
|
|
* @implSpec |
269 |
|
|
* The default implementation is equivalent to the following steps for this |
270 |
|
|
* {@code map}, then returning the current value or {@code null} if now |
271 |
|
|
* absent: |
272 |
|
|
* |
273 |
|
|
* <pre> {@code |
274 |
|
|
* if (map.get(key) == null) { |
275 |
|
|
* V newValue = mappingFunction.apply(key); |
276 |
|
|
* if (newValue != null) |
277 |
|
|
* return map.putIfAbsent(key, newValue); |
278 |
|
|
* } |
279 |
|
|
* }</pre> |
280 |
|
|
* |
281 |
|
|
* The default implementation may retry these steps when multiple |
282 |
|
|
* threads attempt updates, and may call the mapping function |
283 |
|
|
* multiple times. |
284 |
|
|
* |
285 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
286 |
|
|
* @throws ClassCastException {@inheritDoc} |
287 |
|
|
* @throws NullPointerException {@inheritDoc} |
288 |
|
|
* @since 1.8 |
289 |
|
|
*/ |
290 |
|
|
@Override |
291 |
|
|
default V computeIfAbsent(K key, |
292 |
|
|
Function<? super K, ? extends V> mappingFunction) { |
293 |
|
|
Objects.requireNonNull(mappingFunction); |
294 |
|
|
V v, newValue; |
295 |
|
|
return ((v = get(key)) == null && |
296 |
|
|
(newValue = mappingFunction.apply(key)) != null && |
297 |
|
|
(v = putIfAbsent(key, newValue)) == null) ? newValue : v; |
298 |
|
|
} |
299 |
dl |
1.44 |
|
300 |
dl |
1.46 |
/** |
301 |
|
|
* {@inheritDoc} |
302 |
|
|
* |
303 |
|
|
* @implSpec |
304 |
|
|
* The default implementation is equivalent to performing the following |
305 |
|
|
* steps for this {@code map}, then returning the current value or |
306 |
|
|
* {@code null} if now absent. : |
307 |
|
|
* |
308 |
|
|
* <pre> {@code |
309 |
|
|
* if (map.get(key) != null) { |
310 |
|
|
* V oldValue = map.get(key); |
311 |
|
|
* V newValue = remappingFunction.apply(key, oldValue); |
312 |
|
|
* if (newValue != null) |
313 |
|
|
* map.replace(key, oldValue, newValue); |
314 |
|
|
* else |
315 |
|
|
* map.remove(key, oldValue); |
316 |
|
|
* } |
317 |
|
|
* }</pre> |
318 |
|
|
* |
319 |
|
|
* The default implementation may retry these steps when multiple |
320 |
|
|
* threads attempt updates, and may call the remapping function |
321 |
|
|
* multiple times. |
322 |
|
|
* |
323 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
324 |
|
|
* @throws ClassCastException {@inheritDoc} |
325 |
|
|
* @throws NullPointerException {@inheritDoc} |
326 |
|
|
* @since 1.8 |
327 |
|
|
*/ |
328 |
|
|
@Override |
329 |
|
|
default V computeIfPresent(K key, |
330 |
|
|
BiFunction<? super K, ? super V, ? extends V> remappingFunction) { |
331 |
|
|
Objects.requireNonNull(remappingFunction); |
332 |
|
|
V oldValue; |
333 |
jsr166 |
1.47 |
while ((oldValue = get(key)) != null) { |
334 |
dl |
1.46 |
V newValue = remappingFunction.apply(key, oldValue); |
335 |
|
|
if (newValue != null) { |
336 |
|
|
if (replace(key, oldValue, newValue)) |
337 |
|
|
return newValue; |
338 |
|
|
} else if (remove(key, oldValue)) |
339 |
|
|
return null; |
340 |
|
|
} |
341 |
|
|
return oldValue; |
342 |
|
|
} |
343 |
|
|
|
344 |
|
|
/** |
345 |
|
|
* {@inheritDoc} |
346 |
|
|
* |
347 |
|
|
* @implSpec |
348 |
|
|
* The default implementation is equivalent to performing the following |
349 |
|
|
* steps for this {@code map}, then returning the current value or |
350 |
|
|
* {@code null} if absent: |
351 |
|
|
* |
352 |
|
|
* <pre> {@code |
353 |
|
|
* V oldValue = map.get(key); |
354 |
|
|
* V newValue = remappingFunction.apply(key, oldValue); |
355 |
|
|
* if (oldValue != null ) { |
356 |
|
|
* if (newValue != null) |
357 |
|
|
* map.replace(key, oldValue, newValue); |
358 |
|
|
* else |
359 |
|
|
* map.remove(key, oldValue); |
360 |
|
|
* } else { |
361 |
|
|
* if (newValue != null) |
362 |
|
|
* map.putIfAbsent(key, newValue); |
363 |
|
|
* else |
364 |
|
|
* return null; |
365 |
|
|
* } |
366 |
|
|
* }</pre> |
367 |
|
|
* |
368 |
|
|
* The default implementation may retry these steps when multiple |
369 |
|
|
* threads attempt updates, and may call the remapping function |
370 |
|
|
* multiple times. |
371 |
|
|
* |
372 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
373 |
|
|
* @throws ClassCastException {@inheritDoc} |
374 |
|
|
* @throws NullPointerException {@inheritDoc} |
375 |
|
|
* @since 1.8 |
376 |
|
|
*/ |
377 |
|
|
@Override |
378 |
|
|
default V compute(K key, |
379 |
|
|
BiFunction<? super K, ? super V, ? extends V> remappingFunction) { |
380 |
|
|
Objects.requireNonNull(remappingFunction); |
381 |
|
|
V oldValue = get(key); |
382 |
jsr166 |
1.47 |
for (;;) { |
383 |
dl |
1.46 |
V newValue = remappingFunction.apply(key, oldValue); |
384 |
|
|
if (newValue == null) { |
385 |
|
|
// delete mapping |
386 |
|
|
if (oldValue != null || containsKey(key)) { |
387 |
|
|
// something to remove |
388 |
|
|
if (remove(key, oldValue)) { |
389 |
|
|
// removed the old value as expected |
390 |
|
|
return null; |
391 |
|
|
} |
392 |
|
|
|
393 |
|
|
// some other value replaced old value. try again. |
394 |
|
|
oldValue = get(key); |
395 |
|
|
} else { |
396 |
|
|
// nothing to do. Leave things as they were. |
397 |
|
|
return null; |
398 |
|
|
} |
399 |
|
|
} else { |
400 |
|
|
// add or replace old mapping |
401 |
|
|
if (oldValue != null) { |
402 |
|
|
// replace |
403 |
|
|
if (replace(key, oldValue, newValue)) { |
404 |
|
|
// replaced as expected. |
405 |
|
|
return newValue; |
406 |
|
|
} |
407 |
|
|
|
408 |
|
|
// some other value replaced old value. try again. |
409 |
|
|
oldValue = get(key); |
410 |
|
|
} else { |
411 |
|
|
// add (replace if oldValue was null) |
412 |
|
|
if ((oldValue = putIfAbsent(key, newValue)) == null) { |
413 |
|
|
// replaced |
414 |
|
|
return newValue; |
415 |
|
|
} |
416 |
|
|
|
417 |
|
|
// some other value replaced old value. try again. |
418 |
|
|
} |
419 |
dl |
1.44 |
} |
420 |
|
|
} |
421 |
|
|
} |
422 |
|
|
|
423 |
dl |
1.46 |
|
424 |
|
|
/** |
425 |
|
|
* {@inheritDoc} |
426 |
|
|
* |
427 |
|
|
* @implSpec |
428 |
|
|
* The default implementation is equivalent to performing the following |
429 |
|
|
* steps for this {@code map}, then returning the current value or |
430 |
|
|
* {@code null} if absent: |
431 |
|
|
* |
432 |
|
|
* <pre> {@code |
433 |
|
|
* V oldValue = map.get(key); |
434 |
|
|
* V newValue = (oldValue == null) ? value : |
435 |
|
|
* remappingFunction.apply(oldValue, value); |
436 |
|
|
* if (newValue == null) |
437 |
|
|
* map.remove(key); |
438 |
|
|
* else |
439 |
|
|
* map.put(key, newValue); |
440 |
|
|
* }</pre> |
441 |
|
|
* |
442 |
|
|
* The default implementation may retry these steps when multiple |
443 |
|
|
* threads attempt updates, and may call the remapping function |
444 |
|
|
* multiple times. |
445 |
|
|
* |
446 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
447 |
|
|
* @throws ClassCastException {@inheritDoc} |
448 |
|
|
* @throws NullPointerException {@inheritDoc} |
449 |
|
|
* @since 1.8 |
450 |
|
|
*/ |
451 |
|
|
@Override |
452 |
|
|
default V merge(K key, V value, |
453 |
|
|
BiFunction<? super V, ? super V, ? extends V> remappingFunction) { |
454 |
|
|
Objects.requireNonNull(remappingFunction); |
455 |
|
|
Objects.requireNonNull(value); |
456 |
|
|
V oldValue = get(key); |
457 |
|
|
for (;;) { |
458 |
|
|
if (oldValue != null) { |
459 |
|
|
V newValue = remappingFunction.apply(oldValue, value); |
460 |
|
|
if (newValue != null) { |
461 |
|
|
if (replace(key, oldValue, newValue)) |
462 |
|
|
return newValue; |
463 |
|
|
} else if (remove(key, oldValue)) { |
464 |
|
|
return null; |
465 |
|
|
} |
466 |
|
|
oldValue = get(key); |
467 |
|
|
} else { |
468 |
|
|
if ((oldValue = putIfAbsent(key, value)) == null) { |
469 |
|
|
return value; |
470 |
|
|
} |
471 |
|
|
} |
472 |
|
|
} |
473 |
|
|
} |
474 |
tim |
1.1 |
} |