1 |
|
/* |
2 |
|
* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
|
* Expert Group and released to the public domain, as explained at |
4 |
< |
* http://creativecommons.org/licenses/publicdomain |
4 |
> |
* http://creativecommons.org/publicdomain/zero/1.0/ |
5 |
|
*/ |
6 |
|
|
7 |
|
package java.util.concurrent; |
8 |
|
import java.util.concurrent.locks.*; |
9 |
|
import java.util.*; |
10 |
|
import java.io.Serializable; |
11 |
– |
import java.io.IOException; |
12 |
– |
import java.io.ObjectInputStream; |
13 |
– |
import java.io.ObjectOutputStream; |
11 |
|
|
12 |
|
/** |
13 |
|
* A hash table supporting full concurrency of retrievals and |
30 |
|
* removal of only some entries. Similarly, Iterators and |
31 |
|
* Enumerations return elements reflecting the state of the hash table |
32 |
|
* at some point at or since the creation of the iterator/enumeration. |
33 |
< |
* They do <em>not</em> throw |
34 |
< |
* {@link ConcurrentModificationException}. However, iterators are |
38 |
< |
* designed to be used by only one thread at a time. |
33 |
> |
* They do <em>not</em> throw {@link ConcurrentModificationException}. |
34 |
> |
* However, iterators are designed to be used by only one thread at a time. |
35 |
|
* |
36 |
|
* <p> The allowed concurrency among update operations is guided by |
37 |
|
* the optional <tt>concurrencyLevel</tt> constructor argument |
55 |
|
* <em>optional</em> methods of the {@link Map} and {@link Iterator} |
56 |
|
* interfaces. |
57 |
|
* |
58 |
< |
* <p> Like {@link java.util.Hashtable} but unlike {@link |
59 |
< |
* java.util.HashMap}, this class does NOT allow <tt>null</tt> to be |
64 |
< |
* used as a key or value. |
58 |
> |
* <p> Like {@link Hashtable} but unlike {@link HashMap}, this class |
59 |
> |
* does <em>not</em> allow <tt>null</tt> to be used as a key or value. |
60 |
|
* |
61 |
|
* <p>This class is a member of the |
62 |
< |
* <a href="{@docRoot}/../guide/collections/index.html"> |
62 |
> |
* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
63 |
|
* Java Collections Framework</a>. |
64 |
|
* |
65 |
|
* @since 1.5 |
66 |
|
* @author Doug Lea |
67 |
|
* @param <K> the type of keys maintained by this map |
68 |
< |
* @param <V> the type of mapped values |
68 |
> |
* @param <V> the type of mapped values |
69 |
|
*/ |
70 |
|
public class ConcurrentHashMap<K, V> extends AbstractMap<K, V> |
71 |
|
implements ConcurrentMap<K, V>, Serializable { |
73 |
|
|
74 |
|
/* |
75 |
|
* The basic strategy is to subdivide the table among Segments, |
76 |
< |
* each of which itself is a concurrently readable hash table. |
76 |
> |
* each of which itself is a concurrently readable hash table. To |
77 |
> |
* reduce footprint, all but one segments are constructed only |
78 |
> |
* when first needed (see ensureSegment). To maintain visibility |
79 |
> |
* in the presence of lazy construction, accesses to segments as |
80 |
> |
* well as elements of segment's table must use volatile access, |
81 |
> |
* which is done via Unsafe within methods segmentAt etc |
82 |
> |
* below. These provide the functionality of AtomicReferenceArrays |
83 |
> |
* but reduce the levels of indirection. Additionally, |
84 |
> |
* volatile-writes of table elements and entry "next" fields |
85 |
> |
* within locked operations use the cheaper "lazySet" forms of |
86 |
> |
* writes (via putOrderedObject) because these writes are always |
87 |
> |
* followed by lock releases that maintain sequential consistency |
88 |
> |
* of table updates. |
89 |
> |
* |
90 |
> |
* Historical note: The previous version of this class relied |
91 |
> |
* heavily on "final" fields, which avoided some volatile reads at |
92 |
> |
* the expense of a large initial footprint. Some remnants of |
93 |
> |
* that design (including forced construction of segment 0) exist |
94 |
> |
* to ensure serialization compatibility. |
95 |
|
*/ |
96 |
|
|
97 |
|
/* ---------------- Constants -------------- */ |
117 |
|
/** |
118 |
|
* The maximum capacity, used if a higher value is implicitly |
119 |
|
* specified by either of the constructors with arguments. MUST |
120 |
< |
* be a power of two <= 1<<30 to ensure that entries are indexible |
120 |
> |
* be a power of two <= 1<<30 to ensure that entries are indexable |
121 |
|
* using ints. |
122 |
|
*/ |
123 |
< |
static final int MAXIMUM_CAPACITY = 1 << 30; |
123 |
> |
static final int MAXIMUM_CAPACITY = 1 << 30; |
124 |
> |
|
125 |
> |
/** |
126 |
> |
* The minimum capacity for per-segment tables. Must be a power |
127 |
> |
* of two, at least two to avoid immediate resizing on next use |
128 |
> |
* after lazy construction. |
129 |
> |
*/ |
130 |
> |
static final int MIN_SEGMENT_TABLE_CAPACITY = 2; |
131 |
|
|
132 |
|
/** |
133 |
|
* The maximum number of segments to allow; used to bound |
134 |
< |
* constructor arguments. |
134 |
> |
* constructor arguments. Must be power of two less than 1 << 24. |
135 |
|
*/ |
136 |
|
static final int MAX_SEGMENTS = 1 << 16; // slightly conservative |
137 |
|
|
157 |
|
final int segmentShift; |
158 |
|
|
159 |
|
/** |
160 |
< |
* The segments, each of which is a specialized hash table |
160 |
> |
* The segments, each of which is a specialized hash table. |
161 |
|
*/ |
162 |
< |
final Segment[] segments; |
162 |
> |
final Segment<K,V>[] segments; |
163 |
|
|
164 |
|
transient Set<K> keySet; |
165 |
|
transient Set<Map.Entry<K,V>> entrySet; |
166 |
|
transient Collection<V> values; |
167 |
|
|
148 |
– |
/* ---------------- Small Utilities -------------- */ |
149 |
– |
|
150 |
– |
/** |
151 |
– |
* Returns a hash code for non-null Object x. |
152 |
– |
* Uses the same hash code spreader as most other java.util hash tables. |
153 |
– |
* @param x the object serving as a key |
154 |
– |
* @return the hash code |
155 |
– |
*/ |
156 |
– |
static int hash(Object x) { |
157 |
– |
int h = x.hashCode(); |
158 |
– |
h += ~(h << 9); |
159 |
– |
h ^= (h >>> 14); |
160 |
– |
h += (h << 4); |
161 |
– |
h ^= (h >>> 10); |
162 |
– |
return h; |
163 |
– |
} |
164 |
– |
|
165 |
– |
/** |
166 |
– |
* Returns the segment that should be used for key with given hash |
167 |
– |
* @param hash the hash code for the key |
168 |
– |
* @return the segment |
169 |
– |
*/ |
170 |
– |
final Segment<K,V> segmentFor(int hash) { |
171 |
– |
return (Segment<K,V>) segments[(hash >>> segmentShift) & segmentMask]; |
172 |
– |
} |
173 |
– |
|
174 |
– |
/* ---------------- Inner Classes -------------- */ |
175 |
– |
|
168 |
|
/** |
169 |
|
* ConcurrentHashMap list entry. Note that this is never exported |
170 |
< |
* out as a user-visible Map.Entry. |
179 |
< |
* |
180 |
< |
* Because the value field is volatile, not final, it is legal wrt |
181 |
< |
* the Java Memory Model for an unsynchronized reader to see null |
182 |
< |
* instead of initial value when read via a data race. Although a |
183 |
< |
* reordering leading to this is not likely to ever actually |
184 |
< |
* occur, the Segment.readValueUnderLock method is used as a |
185 |
< |
* backup in case a null (pre-initialized) value is ever seen in |
186 |
< |
* an unsynchronized access method. |
170 |
> |
* out as a user-visible Map.Entry. |
171 |
|
*/ |
172 |
|
static final class HashEntry<K,V> { |
189 |
– |
final K key; |
173 |
|
final int hash; |
174 |
+ |
final K key; |
175 |
|
volatile V value; |
176 |
< |
final HashEntry<K,V> next; |
176 |
> |
volatile HashEntry<K,V> next; |
177 |
|
|
178 |
< |
HashEntry(K key, int hash, HashEntry<K,V> next, V value) { |
195 |
< |
this.key = key; |
178 |
> |
HashEntry(int hash, K key, V value, HashEntry<K,V> next) { |
179 |
|
this.hash = hash; |
180 |
< |
this.next = next; |
180 |
> |
this.key = key; |
181 |
|
this.value = value; |
182 |
+ |
this.next = next; |
183 |
+ |
} |
184 |
+ |
|
185 |
+ |
/** |
186 |
+ |
* Sets next field with volatile write semantics. (See above |
187 |
+ |
* about use of putOrderedObject.) |
188 |
+ |
*/ |
189 |
+ |
final void setNext(HashEntry<K,V> n) { |
190 |
+ |
UNSAFE.putOrderedObject(this, nextOffset, n); |
191 |
|
} |
192 |
+ |
|
193 |
+ |
// Unsafe mechanics |
194 |
+ |
static final sun.misc.Unsafe UNSAFE; |
195 |
+ |
static final long nextOffset; |
196 |
+ |
static { |
197 |
+ |
try { |
198 |
+ |
UNSAFE = sun.misc.Unsafe.getUnsafe(); |
199 |
+ |
Class<?> k = HashEntry.class; |
200 |
+ |
nextOffset = UNSAFE.objectFieldOffset |
201 |
+ |
(k.getDeclaredField("next")); |
202 |
+ |
} catch (Exception e) { |
203 |
+ |
throw new Error(e); |
204 |
+ |
} |
205 |
+ |
} |
206 |
+ |
} |
207 |
+ |
|
208 |
+ |
/** |
209 |
+ |
* Gets the ith element of given table (if nonnull) with volatile |
210 |
+ |
* read semantics. Note: This is manually integrated into a few |
211 |
+ |
* performance-sensitive methods to reduce call overhead. |
212 |
+ |
*/ |
213 |
+ |
@SuppressWarnings("unchecked") |
214 |
+ |
static final <K,V> HashEntry<K,V> entryAt(HashEntry<K,V>[] tab, int i) { |
215 |
+ |
return (tab == null) ? null : |
216 |
+ |
(HashEntry<K,V>) UNSAFE.getObjectVolatile |
217 |
+ |
(tab, ((long)i << TSHIFT) + TBASE); |
218 |
+ |
} |
219 |
+ |
|
220 |
+ |
/** |
221 |
+ |
* Sets the ith element of given table, with volatile write |
222 |
+ |
* semantics. (See above about use of putOrderedObject.) |
223 |
+ |
*/ |
224 |
+ |
static final <K,V> void setEntryAt(HashEntry<K,V>[] tab, int i, |
225 |
+ |
HashEntry<K,V> e) { |
226 |
+ |
UNSAFE.putOrderedObject(tab, ((long)i << TSHIFT) + TBASE, e); |
227 |
+ |
} |
228 |
+ |
|
229 |
+ |
/** |
230 |
+ |
* Applies a supplemental hash function to a given hashCode, which |
231 |
+ |
* defends against poor quality hash functions. This is critical |
232 |
+ |
* because ConcurrentHashMap uses power-of-two length hash tables, |
233 |
+ |
* that otherwise encounter collisions for hashCodes that do not |
234 |
+ |
* differ in lower or upper bits. |
235 |
+ |
*/ |
236 |
+ |
private static int hash(int h) { |
237 |
+ |
// Spread bits to regularize both segment and index locations, |
238 |
+ |
// using variant of single-word Wang/Jenkins hash. |
239 |
+ |
h += (h << 15) ^ 0xffffcd7d; |
240 |
+ |
h ^= (h >>> 10); |
241 |
+ |
h += (h << 3); |
242 |
+ |
h ^= (h >>> 6); |
243 |
+ |
h += (h << 2) + (h << 14); |
244 |
+ |
return h ^ (h >>> 16); |
245 |
|
} |
246 |
|
|
247 |
|
/** |
251 |
|
*/ |
252 |
|
static final class Segment<K,V> extends ReentrantLock implements Serializable { |
253 |
|
/* |
254 |
< |
* Segments maintain a table of entry lists that are ALWAYS |
255 |
< |
* kept in a consistent state, so can be read without locking. |
256 |
< |
* Next fields of nodes are immutable (final). All list |
257 |
< |
* additions are performed at the front of each bin. This |
258 |
< |
* makes it easy to check changes, and also fast to traverse. |
259 |
< |
* When nodes would otherwise be changed, new nodes are |
215 |
< |
* created to replace them. This works well for hash tables |
216 |
< |
* since the bin lists tend to be short. (The average length |
217 |
< |
* is less than two for the default load factor threshold.) |
218 |
< |
* |
219 |
< |
* Read operations can thus proceed without locking, but rely |
220 |
< |
* on selected uses of volatiles to ensure that completed |
221 |
< |
* write operations performed by other threads are |
222 |
< |
* noticed. For most purposes, the "count" field, tracking the |
223 |
< |
* number of elements, serves as that volatile variable |
224 |
< |
* ensuring visibility. This is convenient because this field |
225 |
< |
* needs to be read in many read operations anyway: |
226 |
< |
* |
227 |
< |
* - All (unsynchronized) read operations must first read the |
228 |
< |
* "count" field, and should not look at table entries if |
229 |
< |
* it is 0. |
254 |
> |
* Segments maintain a table of entry lists that are always |
255 |
> |
* kept in a consistent state, so can be read (via volatile |
256 |
> |
* reads of segments and tables) without locking. This |
257 |
> |
* requires replicating nodes when necessary during table |
258 |
> |
* resizing, so the old lists can be traversed by readers |
259 |
> |
* still using old version of table. |
260 |
|
* |
261 |
< |
* - All (synchronized) write operations should write to |
262 |
< |
* the "count" field after structurally changing any bin. |
263 |
< |
* The operations must not take any action that could even |
264 |
< |
* momentarily cause a concurrent read operation to see |
265 |
< |
* inconsistent data. This is made easier by the nature of |
266 |
< |
* the read operations in Map. For example, no operation |
267 |
< |
* can reveal that the table has grown but the threshold |
268 |
< |
* has not yet been updated, so there are no atomicity |
269 |
< |
* requirements for this with respect to reads. |
270 |
< |
* |
271 |
< |
* As a guide, all critical volatile reads and writes to the |
272 |
< |
* count field are marked in code comments. |
261 |
> |
* This class defines only mutative methods requiring locking. |
262 |
> |
* Except as noted, the methods of this class perform the |
263 |
> |
* per-segment versions of ConcurrentHashMap methods. (Other |
264 |
> |
* methods are integrated directly into ConcurrentHashMap |
265 |
> |
* methods.) These mutative methods use a form of controlled |
266 |
> |
* spinning on contention via methods scanAndLock and |
267 |
> |
* scanAndLockForPut. These intersperse tryLocks with |
268 |
> |
* traversals to locate nodes. The main benefit is to absorb |
269 |
> |
* cache misses (which are very common for hash tables) while |
270 |
> |
* obtaining locks so that traversal is faster once |
271 |
> |
* acquired. We do not actually use the found nodes since they |
272 |
> |
* must be re-acquired under lock anyway to ensure sequential |
273 |
> |
* consistency of updates (and in any case may be undetectably |
274 |
> |
* stale), but they will normally be much faster to re-locate. |
275 |
> |
* Also, scanAndLockForPut speculatively creates a fresh node |
276 |
> |
* to use in put if no node is found. |
277 |
|
*/ |
278 |
|
|
279 |
|
private static final long serialVersionUID = 2249069246763182397L; |
280 |
|
|
281 |
|
/** |
282 |
< |
* The number of elements in this segment's region. |
282 |
> |
* The maximum number of times to tryLock in a prescan before |
283 |
> |
* possibly blocking on acquire in preparation for a locked |
284 |
> |
* segment operation. On multiprocessors, using a bounded |
285 |
> |
* number of retries maintains cache acquired while locating |
286 |
> |
* nodes. |
287 |
|
*/ |
288 |
< |
transient volatile int count; |
288 |
> |
static final int MAX_SCAN_RETRIES = |
289 |
> |
Runtime.getRuntime().availableProcessors() > 1 ? 64 : 1; |
290 |
|
|
291 |
|
/** |
292 |
< |
* Number of updates that alter the size of the table. This is |
293 |
< |
* used during bulk-read methods to make sure they see a |
255 |
< |
* consistent snapshot: If modCounts change during a traversal |
256 |
< |
* of segments computing size or checking containsValue, then |
257 |
< |
* we might have an inconsistent view of state so (usually) |
258 |
< |
* must retry. |
292 |
> |
* The per-segment table. Elements are accessed via |
293 |
> |
* entryAt/setEntryAt providing volatile semantics. |
294 |
|
*/ |
295 |
< |
transient int modCount; |
295 |
> |
transient volatile HashEntry<K,V>[] table; |
296 |
|
|
297 |
|
/** |
298 |
< |
* The table is rehashed when its size exceeds this threshold. |
299 |
< |
* (The value of this field is always (int)(capacity * |
265 |
< |
* loadFactor).) |
298 |
> |
* The number of elements. Accessed only either within locks |
299 |
> |
* or among other volatile reads that maintain visibility. |
300 |
|
*/ |
301 |
< |
transient int threshold; |
301 |
> |
transient int count; |
302 |
> |
|
303 |
> |
/** |
304 |
> |
* The total number of mutative operations in this segment. |
305 |
> |
* Even though this may overflows 32 bits, it provides |
306 |
> |
* sufficient accuracy for stability checks in CHM isEmpty() |
307 |
> |
* and size() methods. Accessed only either within locks or |
308 |
> |
* among other volatile reads that maintain visibility. |
309 |
> |
*/ |
310 |
> |
transient int modCount; |
311 |
|
|
312 |
|
/** |
313 |
< |
* The per-segment table. Declared as a raw type, casted |
314 |
< |
* to HashEntry<K,V> on each use. |
313 |
> |
* The table is rehashed when its size exceeds this threshold. |
314 |
> |
* (The value of this field is always <tt>(int)(capacity * |
315 |
> |
* loadFactor)</tt>.) |
316 |
|
*/ |
317 |
< |
transient volatile HashEntry[] table; |
317 |
> |
transient int threshold; |
318 |
|
|
319 |
|
/** |
320 |
|
* The load factor for the hash table. Even though this value |
324 |
|
*/ |
325 |
|
final float loadFactor; |
326 |
|
|
327 |
< |
Segment(int initialCapacity, float lf) { |
328 |
< |
loadFactor = lf; |
329 |
< |
setTable(new HashEntry[initialCapacity]); |
327 |
> |
Segment(float lf, int threshold, HashEntry<K,V>[] tab) { |
328 |
> |
this.loadFactor = lf; |
329 |
> |
this.threshold = threshold; |
330 |
> |
this.table = tab; |
331 |
|
} |
332 |
|
|
333 |
< |
/** |
334 |
< |
* Sets table to new HashEntry array. |
335 |
< |
* Call only while holding lock or in constructor. |
336 |
< |
*/ |
292 |
< |
void setTable(HashEntry[] newTable) { |
293 |
< |
threshold = (int)(newTable.length * loadFactor); |
294 |
< |
table = newTable; |
295 |
< |
} |
296 |
< |
|
297 |
< |
/** |
298 |
< |
* Returns properly casted first entry of bin for given hash. |
299 |
< |
*/ |
300 |
< |
HashEntry<K,V> getFirst(int hash) { |
301 |
< |
HashEntry[] tab = table; |
302 |
< |
return (HashEntry<K,V>) tab[hash & (tab.length - 1)]; |
303 |
< |
} |
304 |
< |
|
305 |
< |
/** |
306 |
< |
* Reads value field of an entry under lock. Called if value |
307 |
< |
* field ever appears to be null. This is possible only if a |
308 |
< |
* compiler happens to reorder a HashEntry initialization with |
309 |
< |
* its table assignment, which is legal under memory model |
310 |
< |
* but is not known to ever occur. |
311 |
< |
*/ |
312 |
< |
V readValueUnderLock(HashEntry<K,V> e) { |
313 |
< |
lock(); |
333 |
> |
final V put(K key, int hash, V value, boolean onlyIfAbsent) { |
334 |
> |
HashEntry<K,V> node = tryLock() ? null : |
335 |
> |
scanAndLockForPut(key, hash, value); |
336 |
> |
V oldValue; |
337 |
|
try { |
338 |
< |
return e.value; |
339 |
< |
} finally { |
340 |
< |
unlock(); |
341 |
< |
} |
342 |
< |
} |
343 |
< |
|
344 |
< |
/* Specialized implementations of map methods */ |
345 |
< |
|
346 |
< |
V get(Object key, int hash) { |
347 |
< |
if (count != 0) { // read-volatile |
348 |
< |
HashEntry<K,V> e = getFirst(hash); |
349 |
< |
while (e != null) { |
350 |
< |
if (e.hash == hash && key.equals(e.key)) { |
351 |
< |
V v = e.value; |
352 |
< |
if (v != null) |
353 |
< |
return v; |
331 |
< |
return readValueUnderLock(e); // recheck |
338 |
> |
HashEntry<K,V>[] tab = table; |
339 |
> |
int index = (tab.length - 1) & hash; |
340 |
> |
HashEntry<K,V> first = entryAt(tab, index); |
341 |
> |
for (HashEntry<K,V> e = first;;) { |
342 |
> |
if (e != null) { |
343 |
> |
K k; |
344 |
> |
if ((k = e.key) == key || |
345 |
> |
(e.hash == hash && key.equals(k))) { |
346 |
> |
oldValue = e.value; |
347 |
> |
if (!onlyIfAbsent) { |
348 |
> |
e.value = value; |
349 |
> |
++modCount; |
350 |
> |
} |
351 |
> |
break; |
352 |
> |
} |
353 |
> |
e = e.next; |
354 |
|
} |
355 |
< |
e = e.next; |
356 |
< |
} |
357 |
< |
} |
358 |
< |
return null; |
359 |
< |
} |
360 |
< |
|
361 |
< |
boolean containsKey(Object key, int hash) { |
362 |
< |
if (count != 0) { // read-volatile |
363 |
< |
HashEntry<K,V> e = getFirst(hash); |
364 |
< |
while (e != null) { |
365 |
< |
if (e.hash == hash && key.equals(e.key)) |
366 |
< |
return true; |
367 |
< |
e = e.next; |
368 |
< |
} |
347 |
< |
} |
348 |
< |
return false; |
349 |
< |
} |
350 |
< |
|
351 |
< |
boolean containsValue(Object value) { |
352 |
< |
if (count != 0) { // read-volatile |
353 |
< |
HashEntry[] tab = table; |
354 |
< |
int len = tab.length; |
355 |
< |
for (int i = 0 ; i < len; i++) { |
356 |
< |
for (HashEntry<K,V> e = (HashEntry<K,V>)tab[i]; |
357 |
< |
e != null ; |
358 |
< |
e = e.next) { |
359 |
< |
V v = e.value; |
360 |
< |
if (v == null) // recheck |
361 |
< |
v = readValueUnderLock(e); |
362 |
< |
if (value.equals(v)) |
363 |
< |
return true; |
355 |
> |
else { |
356 |
> |
if (node != null) |
357 |
> |
node.setNext(first); |
358 |
> |
else |
359 |
> |
node = new HashEntry<K,V>(hash, key, value, first); |
360 |
> |
int c = count + 1; |
361 |
> |
if (c > threshold && tab.length < MAXIMUM_CAPACITY) |
362 |
> |
rehash(node); |
363 |
> |
else |
364 |
> |
setEntryAt(tab, index, node); |
365 |
> |
++modCount; |
366 |
> |
count = c; |
367 |
> |
oldValue = null; |
368 |
> |
break; |
369 |
|
} |
370 |
|
} |
366 |
– |
} |
367 |
– |
return false; |
368 |
– |
} |
369 |
– |
|
370 |
– |
boolean replace(K key, int hash, V oldValue, V newValue) { |
371 |
– |
lock(); |
372 |
– |
try { |
373 |
– |
HashEntry<K,V> e = getFirst(hash); |
374 |
– |
while (e != null && (e.hash != hash || !key.equals(e.key))) |
375 |
– |
e = e.next; |
376 |
– |
|
377 |
– |
boolean replaced = false; |
378 |
– |
if (e != null && oldValue.equals(e.value)) { |
379 |
– |
replaced = true; |
380 |
– |
e.value = newValue; |
381 |
– |
} |
382 |
– |
return replaced; |
383 |
– |
} finally { |
384 |
– |
unlock(); |
385 |
– |
} |
386 |
– |
} |
387 |
– |
|
388 |
– |
V replace(K key, int hash, V newValue) { |
389 |
– |
lock(); |
390 |
– |
try { |
391 |
– |
HashEntry<K,V> e = getFirst(hash); |
392 |
– |
while (e != null && (e.hash != hash || !key.equals(e.key))) |
393 |
– |
e = e.next; |
394 |
– |
|
395 |
– |
V oldValue = null; |
396 |
– |
if (e != null) { |
397 |
– |
oldValue = e.value; |
398 |
– |
e.value = newValue; |
399 |
– |
} |
400 |
– |
return oldValue; |
401 |
– |
} finally { |
402 |
– |
unlock(); |
403 |
– |
} |
404 |
– |
} |
405 |
– |
|
406 |
– |
|
407 |
– |
V put(K key, int hash, V value, boolean onlyIfAbsent) { |
408 |
– |
lock(); |
409 |
– |
try { |
410 |
– |
int c = count; |
411 |
– |
if (c++ > threshold) // ensure capacity |
412 |
– |
rehash(); |
413 |
– |
HashEntry[] tab = table; |
414 |
– |
int index = hash & (tab.length - 1); |
415 |
– |
HashEntry<K,V> first = (HashEntry<K,V>) tab[index]; |
416 |
– |
HashEntry<K,V> e = first; |
417 |
– |
while (e != null && (e.hash != hash || !key.equals(e.key))) |
418 |
– |
e = e.next; |
419 |
– |
|
420 |
– |
V oldValue; |
421 |
– |
if (e != null) { |
422 |
– |
oldValue = e.value; |
423 |
– |
if (!onlyIfAbsent) |
424 |
– |
e.value = value; |
425 |
– |
} |
426 |
– |
else { |
427 |
– |
oldValue = null; |
428 |
– |
++modCount; |
429 |
– |
tab[index] = new HashEntry<K,V>(key, hash, first, value); |
430 |
– |
count = c; // write-volatile |
431 |
– |
} |
432 |
– |
return oldValue; |
371 |
|
} finally { |
372 |
|
unlock(); |
373 |
|
} |
374 |
+ |
return oldValue; |
375 |
|
} |
376 |
|
|
377 |
< |
void rehash() { |
378 |
< |
HashEntry[] oldTable = table; |
379 |
< |
int oldCapacity = oldTable.length; |
380 |
< |
if (oldCapacity >= MAXIMUM_CAPACITY) |
381 |
< |
return; |
382 |
< |
|
377 |
> |
/** |
378 |
> |
* Doubles size of table and repacks entries, also adding the |
379 |
> |
* given node to new table |
380 |
> |
*/ |
381 |
> |
@SuppressWarnings("unchecked") |
382 |
> |
private void rehash(HashEntry<K,V> node) { |
383 |
|
/* |
384 |
< |
* Reclassify nodes in each list to new Map. Because we are |
385 |
< |
* using power-of-two expansion, the elements from each bin |
386 |
< |
* must either stay at same index, or move with a power of two |
387 |
< |
* offset. We eliminate unnecessary node creation by catching |
388 |
< |
* cases where old nodes can be reused because their next |
389 |
< |
* fields won't change. Statistically, at the default |
390 |
< |
* threshold, only about one-sixth of them need cloning when |
391 |
< |
* a table doubles. The nodes they replace will be garbage |
392 |
< |
* collectable as soon as they are no longer referenced by any |
393 |
< |
* reader thread that may be in the midst of traversing table |
394 |
< |
* right now. |
384 |
> |
* Reclassify nodes in each list to new table. Because we |
385 |
> |
* are using power-of-two expansion, the elements from |
386 |
> |
* each bin must either stay at same index, or move with a |
387 |
> |
* power of two offset. We eliminate unnecessary node |
388 |
> |
* creation by catching cases where old nodes can be |
389 |
> |
* reused because their next fields won't change. |
390 |
> |
* Statistically, at the default threshold, only about |
391 |
> |
* one-sixth of them need cloning when a table |
392 |
> |
* doubles. The nodes they replace will be garbage |
393 |
> |
* collectable as soon as they are no longer referenced by |
394 |
> |
* any reader thread that may be in the midst of |
395 |
> |
* concurrently traversing table. Entry accesses use plain |
396 |
> |
* array indexing because they are followed by volatile |
397 |
> |
* table write. |
398 |
|
*/ |
399 |
< |
|
400 |
< |
HashEntry[] newTable = new HashEntry[oldCapacity << 1]; |
401 |
< |
threshold = (int)(newTable.length * loadFactor); |
402 |
< |
int sizeMask = newTable.length - 1; |
399 |
> |
HashEntry<K,V>[] oldTable = table; |
400 |
> |
int oldCapacity = oldTable.length; |
401 |
> |
int newCapacity = oldCapacity << 1; |
402 |
> |
threshold = (int)(newCapacity * loadFactor); |
403 |
> |
HashEntry<K,V>[] newTable = |
404 |
> |
(HashEntry<K,V>[]) new HashEntry<?,?>[newCapacity]; |
405 |
> |
int sizeMask = newCapacity - 1; |
406 |
|
for (int i = 0; i < oldCapacity ; i++) { |
407 |
< |
// We need to guarantee that any existing reads of old Map can |
463 |
< |
// proceed. So we cannot yet null out each bin. |
464 |
< |
HashEntry<K,V> e = (HashEntry<K,V>)oldTable[i]; |
465 |
< |
|
407 |
> |
HashEntry<K,V> e = oldTable[i]; |
408 |
|
if (e != null) { |
409 |
|
HashEntry<K,V> next = e.next; |
410 |
|
int idx = e.hash & sizeMask; |
411 |
< |
|
470 |
< |
// Single node on list |
471 |
< |
if (next == null) |
411 |
> |
if (next == null) // Single node on list |
412 |
|
newTable[idx] = e; |
413 |
< |
|
474 |
< |
else { |
475 |
< |
// Reuse trailing consecutive sequence at same slot |
413 |
> |
else { // Reuse consecutive sequence at same slot |
414 |
|
HashEntry<K,V> lastRun = e; |
415 |
|
int lastIdx = idx; |
416 |
|
for (HashEntry<K,V> last = next; |
423 |
|
} |
424 |
|
} |
425 |
|
newTable[lastIdx] = lastRun; |
426 |
< |
|
489 |
< |
// Clone all remaining nodes |
426 |
> |
// Clone remaining nodes |
427 |
|
for (HashEntry<K,V> p = e; p != lastRun; p = p.next) { |
428 |
< |
int k = p.hash & sizeMask; |
429 |
< |
HashEntry<K,V> n = (HashEntry<K,V>)newTable[k]; |
430 |
< |
newTable[k] = new HashEntry<K,V>(p.key, p.hash, |
431 |
< |
n, p.value); |
428 |
> |
V v = p.value; |
429 |
> |
int h = p.hash; |
430 |
> |
int k = h & sizeMask; |
431 |
> |
HashEntry<K,V> n = newTable[k]; |
432 |
> |
newTable[k] = new HashEntry<K,V>(h, p.key, v, n); |
433 |
|
} |
434 |
|
} |
435 |
|
} |
436 |
|
} |
437 |
+ |
int nodeIndex = node.hash & sizeMask; // add the new node |
438 |
+ |
node.setNext(newTable[nodeIndex]); |
439 |
+ |
newTable[nodeIndex] = node; |
440 |
|
table = newTable; |
441 |
|
} |
442 |
|
|
443 |
|
/** |
444 |
+ |
* Scans for a node containing given key while trying to |
445 |
+ |
* acquire lock, creating and returning one if not found. Upon |
446 |
+ |
* return, guarantees that lock is held. Unlike in most |
447 |
+ |
* methods, calls to method equals are not screened: Since |
448 |
+ |
* traversal speed doesn't matter, we might as well help warm |
449 |
+ |
* up the associated code and accesses as well. |
450 |
+ |
* |
451 |
+ |
* @return a new node if key not found, else null |
452 |
+ |
*/ |
453 |
+ |
private HashEntry<K,V> scanAndLockForPut(K key, int hash, V value) { |
454 |
+ |
HashEntry<K,V> first = entryForHash(this, hash); |
455 |
+ |
HashEntry<K,V> e = first; |
456 |
+ |
HashEntry<K,V> node = null; |
457 |
+ |
int retries = -1; // negative while locating node |
458 |
+ |
while (!tryLock()) { |
459 |
+ |
HashEntry<K,V> f; // to recheck first below |
460 |
+ |
if (retries < 0) { |
461 |
+ |
if (e == null) { |
462 |
+ |
if (node == null) // speculatively create node |
463 |
+ |
node = new HashEntry<K,V>(hash, key, value, null); |
464 |
+ |
retries = 0; |
465 |
+ |
} |
466 |
+ |
else if (key.equals(e.key)) |
467 |
+ |
retries = 0; |
468 |
+ |
else |
469 |
+ |
e = e.next; |
470 |
+ |
} |
471 |
+ |
else if (++retries > MAX_SCAN_RETRIES) { |
472 |
+ |
lock(); |
473 |
+ |
break; |
474 |
+ |
} |
475 |
+ |
else if ((retries & 1) == 0 && |
476 |
+ |
(f = entryForHash(this, hash)) != first) { |
477 |
+ |
e = first = f; // re-traverse if entry changed |
478 |
+ |
retries = -1; |
479 |
+ |
} |
480 |
+ |
} |
481 |
+ |
return node; |
482 |
+ |
} |
483 |
+ |
|
484 |
+ |
/** |
485 |
+ |
* Scans for a node containing the given key while trying to |
486 |
+ |
* acquire lock for a remove or replace operation. Upon |
487 |
+ |
* return, guarantees that lock is held. Note that we must |
488 |
+ |
* lock even if the key is not found, to ensure sequential |
489 |
+ |
* consistency of updates. |
490 |
+ |
*/ |
491 |
+ |
private void scanAndLock(Object key, int hash) { |
492 |
+ |
// similar to but simpler than scanAndLockForPut |
493 |
+ |
HashEntry<K,V> first = entryForHash(this, hash); |
494 |
+ |
HashEntry<K,V> e = first; |
495 |
+ |
int retries = -1; |
496 |
+ |
while (!tryLock()) { |
497 |
+ |
HashEntry<K,V> f; |
498 |
+ |
if (retries < 0) { |
499 |
+ |
if (e == null || key.equals(e.key)) |
500 |
+ |
retries = 0; |
501 |
+ |
else |
502 |
+ |
e = e.next; |
503 |
+ |
} |
504 |
+ |
else if (++retries > MAX_SCAN_RETRIES) { |
505 |
+ |
lock(); |
506 |
+ |
break; |
507 |
+ |
} |
508 |
+ |
else if ((retries & 1) == 0 && |
509 |
+ |
(f = entryForHash(this, hash)) != first) { |
510 |
+ |
e = first = f; |
511 |
+ |
retries = -1; |
512 |
+ |
} |
513 |
+ |
} |
514 |
+ |
} |
515 |
+ |
|
516 |
+ |
/** |
517 |
|
* Remove; match on key only if value null, else match both. |
518 |
|
*/ |
519 |
< |
V remove(Object key, int hash, Object value) { |
520 |
< |
lock(); |
519 |
> |
final V remove(Object key, int hash, Object value) { |
520 |
> |
if (!tryLock()) |
521 |
> |
scanAndLock(key, hash); |
522 |
> |
V oldValue = null; |
523 |
|
try { |
524 |
< |
int c = count - 1; |
525 |
< |
HashEntry[] tab = table; |
526 |
< |
int index = hash & (tab.length - 1); |
527 |
< |
HashEntry<K,V> first = (HashEntry<K,V>)tab[index]; |
528 |
< |
HashEntry<K,V> e = first; |
529 |
< |
while (e != null && (e.hash != hash || !key.equals(e.key))) |
530 |
< |
e = e.next; |
524 |
> |
HashEntry<K,V>[] tab = table; |
525 |
> |
int index = (tab.length - 1) & hash; |
526 |
> |
HashEntry<K,V> e = entryAt(tab, index); |
527 |
> |
HashEntry<K,V> pred = null; |
528 |
> |
while (e != null) { |
529 |
> |
K k; |
530 |
> |
HashEntry<K,V> next = e.next; |
531 |
> |
if ((k = e.key) == key || |
532 |
> |
(e.hash == hash && key.equals(k))) { |
533 |
> |
V v = e.value; |
534 |
> |
if (value == null || value == v || value.equals(v)) { |
535 |
> |
if (pred == null) |
536 |
> |
setEntryAt(tab, index, next); |
537 |
> |
else |
538 |
> |
pred.setNext(next); |
539 |
> |
++modCount; |
540 |
> |
--count; |
541 |
> |
oldValue = v; |
542 |
> |
} |
543 |
> |
break; |
544 |
> |
} |
545 |
> |
pred = e; |
546 |
> |
e = next; |
547 |
> |
} |
548 |
> |
} finally { |
549 |
> |
unlock(); |
550 |
> |
} |
551 |
> |
return oldValue; |
552 |
> |
} |
553 |
|
|
554 |
< |
V oldValue = null; |
555 |
< |
if (e != null) { |
556 |
< |
V v = e.value; |
557 |
< |
if (value == null || value.equals(v)) { |
558 |
< |
oldValue = v; |
559 |
< |
// All entries following removed node can stay |
560 |
< |
// in list, but all preceding ones need to be |
561 |
< |
// cloned. |
554 |
> |
final boolean replace(K key, int hash, V oldValue, V newValue) { |
555 |
> |
if (!tryLock()) |
556 |
> |
scanAndLock(key, hash); |
557 |
> |
boolean replaced = false; |
558 |
> |
try { |
559 |
> |
HashEntry<K,V> e; |
560 |
> |
for (e = entryForHash(this, hash); e != null; e = e.next) { |
561 |
> |
K k; |
562 |
> |
if ((k = e.key) == key || |
563 |
> |
(e.hash == hash && key.equals(k))) { |
564 |
> |
if (oldValue.equals(e.value)) { |
565 |
> |
e.value = newValue; |
566 |
> |
++modCount; |
567 |
> |
replaced = true; |
568 |
> |
} |
569 |
> |
break; |
570 |
> |
} |
571 |
> |
} |
572 |
> |
} finally { |
573 |
> |
unlock(); |
574 |
> |
} |
575 |
> |
return replaced; |
576 |
> |
} |
577 |
> |
|
578 |
> |
final V replace(K key, int hash, V value) { |
579 |
> |
if (!tryLock()) |
580 |
> |
scanAndLock(key, hash); |
581 |
> |
V oldValue = null; |
582 |
> |
try { |
583 |
> |
HashEntry<K,V> e; |
584 |
> |
for (e = entryForHash(this, hash); e != null; e = e.next) { |
585 |
> |
K k; |
586 |
> |
if ((k = e.key) == key || |
587 |
> |
(e.hash == hash && key.equals(k))) { |
588 |
> |
oldValue = e.value; |
589 |
> |
e.value = value; |
590 |
|
++modCount; |
591 |
< |
HashEntry<K,V> newFirst = e.next; |
526 |
< |
for (HashEntry<K,V> p = first; p != e; p = p.next) |
527 |
< |
newFirst = new HashEntry<K,V>(p.key, p.hash, |
528 |
< |
newFirst, p.value); |
529 |
< |
tab[index] = newFirst; |
530 |
< |
count = c; // write-volatile |
591 |
> |
break; |
592 |
|
} |
593 |
|
} |
594 |
< |
return oldValue; |
594 |
> |
} finally { |
595 |
> |
unlock(); |
596 |
> |
} |
597 |
> |
return oldValue; |
598 |
> |
} |
599 |
> |
|
600 |
> |
final void clear() { |
601 |
> |
lock(); |
602 |
> |
try { |
603 |
> |
HashEntry<K,V>[] tab = table; |
604 |
> |
for (int i = 0; i < tab.length ; i++) |
605 |
> |
setEntryAt(tab, i, null); |
606 |
> |
++modCount; |
607 |
> |
count = 0; |
608 |
|
} finally { |
609 |
|
unlock(); |
610 |
|
} |
611 |
|
} |
612 |
+ |
} |
613 |
|
|
614 |
< |
void clear() { |
615 |
< |
if (count != 0) { |
616 |
< |
lock(); |
617 |
< |
try { |
618 |
< |
HashEntry[] tab = table; |
619 |
< |
for (int i = 0; i < tab.length ; i++) |
620 |
< |
tab[i] = null; |
621 |
< |
++modCount; |
622 |
< |
count = 0; // write-volatile |
623 |
< |
} finally { |
624 |
< |
unlock(); |
614 |
> |
// Accessing segments |
615 |
> |
|
616 |
> |
/** |
617 |
> |
* Gets the jth element of given segment array (if nonnull) with |
618 |
> |
* volatile element access semantics via Unsafe. (The null check |
619 |
> |
* can trigger harmlessly only during deserialization.) Note: |
620 |
> |
* because each element of segments array is set only once (using |
621 |
> |
* fully ordered writes), some performance-sensitive methods rely |
622 |
> |
* on this method only as a recheck upon null reads. |
623 |
> |
*/ |
624 |
> |
@SuppressWarnings("unchecked") |
625 |
> |
static final <K,V> Segment<K,V> segmentAt(Segment<K,V>[] ss, int j) { |
626 |
> |
long u = (j << SSHIFT) + SBASE; |
627 |
> |
return ss == null ? null : |
628 |
> |
(Segment<K,V>) UNSAFE.getObjectVolatile(ss, u); |
629 |
> |
} |
630 |
> |
|
631 |
> |
/** |
632 |
> |
* Returns the segment for the given index, creating it and |
633 |
> |
* recording in segment table (via CAS) if not already present. |
634 |
> |
* |
635 |
> |
* @param k the index |
636 |
> |
* @return the segment |
637 |
> |
*/ |
638 |
> |
@SuppressWarnings("unchecked") |
639 |
> |
private Segment<K,V> ensureSegment(int k) { |
640 |
> |
final Segment<K,V>[] ss = this.segments; |
641 |
> |
long u = (k << SSHIFT) + SBASE; // raw offset |
642 |
> |
Segment<K,V> seg; |
643 |
> |
if ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u)) == null) { |
644 |
> |
Segment<K,V> proto = ss[0]; // use segment 0 as prototype |
645 |
> |
int cap = proto.table.length; |
646 |
> |
float lf = proto.loadFactor; |
647 |
> |
int threshold = (int)(cap * lf); |
648 |
> |
HashEntry<K,V>[] tab = (HashEntry<K,V>[])new HashEntry<?,?>[cap]; |
649 |
> |
if ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u)) |
650 |
> |
== null) { // recheck |
651 |
> |
Segment<K,V> s = new Segment<K,V>(lf, threshold, tab); |
652 |
> |
while ((seg = (Segment<K,V>)UNSAFE.getObjectVolatile(ss, u)) |
653 |
> |
== null) { |
654 |
> |
if (UNSAFE.compareAndSwapObject(ss, u, null, seg = s)) |
655 |
> |
break; |
656 |
|
} |
657 |
|
} |
658 |
|
} |
659 |
+ |
return seg; |
660 |
|
} |
661 |
|
|
662 |
+ |
// Hash-based segment and entry accesses |
663 |
|
|
664 |
+ |
/** |
665 |
+ |
* Gets the segment for the given hash code. |
666 |
+ |
*/ |
667 |
+ |
@SuppressWarnings("unchecked") |
668 |
+ |
private Segment<K,V> segmentForHash(int h) { |
669 |
+ |
long u = (((h >>> segmentShift) & segmentMask) << SSHIFT) + SBASE; |
670 |
+ |
return (Segment<K,V>) UNSAFE.getObjectVolatile(segments, u); |
671 |
+ |
} |
672 |
+ |
|
673 |
+ |
/** |
674 |
+ |
* Gets the table entry for the given segment and hash code. |
675 |
+ |
*/ |
676 |
+ |
@SuppressWarnings("unchecked") |
677 |
+ |
static final <K,V> HashEntry<K,V> entryForHash(Segment<K,V> seg, int h) { |
678 |
+ |
HashEntry<K,V>[] tab; |
679 |
+ |
return (seg == null || (tab = seg.table) == null) ? null : |
680 |
+ |
(HashEntry<K,V>) UNSAFE.getObjectVolatile |
681 |
+ |
(tab, ((long)(((tab.length - 1) & h)) << TSHIFT) + TBASE); |
682 |
+ |
} |
683 |
|
|
684 |
|
/* ---------------- Public operations -------------- */ |
685 |
|
|
694 |
|
* bin exceeds this threshold. |
695 |
|
* @param concurrencyLevel the estimated number of concurrently |
696 |
|
* updating threads. The implementation performs internal sizing |
697 |
< |
* to try to accommodate this many threads. |
697 |
> |
* to try to accommodate this many threads. |
698 |
|
* @throws IllegalArgumentException if the initial capacity is |
699 |
|
* negative or the load factor or concurrencyLevel are |
700 |
|
* nonpositive. |
701 |
|
*/ |
702 |
+ |
@SuppressWarnings("unchecked") |
703 |
|
public ConcurrentHashMap(int initialCapacity, |
704 |
|
float loadFactor, int concurrencyLevel) { |
705 |
|
if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0) |
706 |
|
throw new IllegalArgumentException(); |
579 |
– |
|
707 |
|
if (concurrencyLevel > MAX_SEGMENTS) |
708 |
|
concurrencyLevel = MAX_SEGMENTS; |
582 |
– |
|
709 |
|
// Find power-of-two sizes best matching arguments |
710 |
|
int sshift = 0; |
711 |
|
int ssize = 1; |
713 |
|
++sshift; |
714 |
|
ssize <<= 1; |
715 |
|
} |
716 |
< |
segmentShift = 32 - sshift; |
717 |
< |
segmentMask = ssize - 1; |
592 |
< |
this.segments = new Segment[ssize]; |
593 |
< |
|
716 |
> |
this.segmentShift = 32 - sshift; |
717 |
> |
this.segmentMask = ssize - 1; |
718 |
|
if (initialCapacity > MAXIMUM_CAPACITY) |
719 |
|
initialCapacity = MAXIMUM_CAPACITY; |
720 |
|
int c = initialCapacity / ssize; |
721 |
|
if (c * ssize < initialCapacity) |
722 |
|
++c; |
723 |
< |
int cap = 1; |
723 |
> |
int cap = MIN_SEGMENT_TABLE_CAPACITY; |
724 |
|
while (cap < c) |
725 |
|
cap <<= 1; |
726 |
< |
|
727 |
< |
for (int i = 0; i < this.segments.length; ++i) |
728 |
< |
this.segments[i] = new Segment<K,V>(cap, loadFactor); |
726 |
> |
// create segments and segments[0] |
727 |
> |
Segment<K,V> s0 = |
728 |
> |
new Segment<K,V>(loadFactor, (int)(cap * loadFactor), |
729 |
> |
(HashEntry<K,V>[])new HashEntry<?,?>[cap]); |
730 |
> |
Segment<K,V>[] ss = (Segment<K,V>[])new Segment<?,?>[ssize]; |
731 |
> |
UNSAFE.putOrderedObject(ss, SBASE, s0); // ordered write of segments[0] |
732 |
> |
this.segments = ss; |
733 |
|
} |
734 |
|
|
735 |
|
/** |
736 |
|
* Creates a new, empty map with the specified initial capacity |
737 |
< |
* and load factor and with the default concurrencyLevel |
610 |
< |
* (<tt>16</tt>). |
737 |
> |
* and load factor and with the default concurrencyLevel (16). |
738 |
|
* |
739 |
|
* @param initialCapacity The implementation performs internal |
740 |
|
* sizing to accommodate this many elements. |
741 |
|
* @param loadFactor the load factor threshold, used to control resizing. |
742 |
+ |
* Resizing may be performed when the average number of elements per |
743 |
+ |
* bin exceeds this threshold. |
744 |
|
* @throws IllegalArgumentException if the initial capacity of |
745 |
|
* elements is negative or the load factor is nonpositive |
746 |
+ |
* |
747 |
+ |
* @since 1.6 |
748 |
|
*/ |
749 |
|
public ConcurrentHashMap(int initialCapacity, float loadFactor) { |
750 |
|
this(initialCapacity, loadFactor, DEFAULT_CONCURRENCY_LEVEL); |
752 |
|
|
753 |
|
/** |
754 |
|
* Creates a new, empty map with the specified initial capacity, |
755 |
< |
* and with default load factor (<tt>0.75f</tt>) |
625 |
< |
* and concurrencyLevel (<tt>16</tt>). |
755 |
> |
* and with default load factor (0.75) and concurrencyLevel (16). |
756 |
|
* |
757 |
|
* @param initialCapacity the initial capacity. The implementation |
758 |
|
* performs internal sizing to accommodate this many elements. |
764 |
|
} |
765 |
|
|
766 |
|
/** |
767 |
< |
* Creates a new, empty map with a default initial capacity |
768 |
< |
* (<tt>16</tt>), load factor |
639 |
< |
* (<tt>0.75f</tt>), and concurrencyLevel |
640 |
< |
* (<tt>16</tt>). |
767 |
> |
* Creates a new, empty map with a default initial capacity (16), |
768 |
> |
* load factor (0.75) and concurrencyLevel (16). |
769 |
|
*/ |
770 |
|
public ConcurrentHashMap() { |
771 |
|
this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
772 |
|
} |
773 |
|
|
774 |
|
/** |
775 |
< |
* Creates a new map with the same mappings as the given map. The |
776 |
< |
* map is created with a capacity of 1.5 times the number of |
777 |
< |
* mappings in the given map or <tt>16</tt> |
778 |
< |
* (whichever is greater), and a default load factor |
779 |
< |
* (<tt>0.75f</tt>) and concurrencyLevel |
780 |
< |
* (<tt>16</tt>). |
653 |
< |
* @param t the map |
775 |
> |
* Creates a new map with the same mappings as the given map. |
776 |
> |
* The map is created with a capacity of 1.5 times the number |
777 |
> |
* of mappings in the given map or 16 (whichever is greater), |
778 |
> |
* and a default load factor (0.75) and concurrencyLevel (16). |
779 |
> |
* |
780 |
> |
* @param m the map |
781 |
|
*/ |
782 |
< |
public ConcurrentHashMap(Map<? extends K, ? extends V> t) { |
783 |
< |
this(Math.max((int) (t.size() / DEFAULT_LOAD_FACTOR) + 1, |
782 |
> |
public ConcurrentHashMap(Map<? extends K, ? extends V> m) { |
783 |
> |
this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1, |
784 |
|
DEFAULT_INITIAL_CAPACITY), |
785 |
|
DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
786 |
< |
putAll(t); |
786 |
> |
putAll(m); |
787 |
|
} |
788 |
|
|
789 |
|
/** |
790 |
|
* Returns <tt>true</tt> if this map contains no key-value mappings. |
791 |
|
* |
792 |
< |
* @return <tt>true</tt> if this map contains no key-value mappings. |
792 |
> |
* @return <tt>true</tt> if this map contains no key-value mappings |
793 |
|
*/ |
794 |
|
public boolean isEmpty() { |
668 |
– |
final Segment[] segments = this.segments; |
795 |
|
/* |
796 |
< |
* We keep track of per-segment modCounts to avoid ABA |
797 |
< |
* problems in which an element in one segment was added and |
798 |
< |
* in another removed during traversal, in which case the |
799 |
< |
* table was never actually empty at any point. Note the |
800 |
< |
* similar use of modCounts in the size() and containsValue() |
801 |
< |
* methods, which are the only other methods also susceptible |
802 |
< |
* to ABA problems. |
796 |
> |
* Sum per-segment modCounts to avoid mis-reporting when |
797 |
> |
* elements are concurrently added and removed in one segment |
798 |
> |
* while checking another, in which case the table was never |
799 |
> |
* actually empty at any point. (The sum ensures accuracy up |
800 |
> |
* through at least 1<<31 per-segment modifications before |
801 |
> |
* recheck.) Methods size() and containsValue() use similar |
802 |
> |
* constructions for stability checks. |
803 |
|
*/ |
804 |
< |
int[] mc = new int[segments.length]; |
805 |
< |
int mcsum = 0; |
806 |
< |
for (int i = 0; i < segments.length; ++i) { |
807 |
< |
if (segments[i].count != 0) |
808 |
< |
return false; |
809 |
< |
else |
684 |
< |
mcsum += mc[i] = segments[i].modCount; |
685 |
< |
} |
686 |
< |
// If mcsum happens to be zero, then we know we got a snapshot |
687 |
< |
// before any modifications at all were made. This is |
688 |
< |
// probably common enough to bother tracking. |
689 |
< |
if (mcsum != 0) { |
690 |
< |
for (int i = 0; i < segments.length; ++i) { |
691 |
< |
if (segments[i].count != 0 || |
692 |
< |
mc[i] != segments[i].modCount) |
804 |
> |
long sum = 0L; |
805 |
> |
final Segment<K,V>[] segments = this.segments; |
806 |
> |
for (int j = 0; j < segments.length; ++j) { |
807 |
> |
Segment<K,V> seg = segmentAt(segments, j); |
808 |
> |
if (seg != null) { |
809 |
> |
if (seg.count != 0) |
810 |
|
return false; |
811 |
+ |
sum += seg.modCount; |
812 |
+ |
} |
813 |
+ |
} |
814 |
+ |
if (sum != 0L) { // recheck unless no modifications |
815 |
+ |
for (int j = 0; j < segments.length; ++j) { |
816 |
+ |
Segment<K,V> seg = segmentAt(segments, j); |
817 |
+ |
if (seg != null) { |
818 |
+ |
if (seg.count != 0) |
819 |
+ |
return false; |
820 |
+ |
sum -= seg.modCount; |
821 |
+ |
} |
822 |
|
} |
823 |
+ |
if (sum != 0L) |
824 |
+ |
return false; |
825 |
|
} |
826 |
|
return true; |
827 |
|
} |
831 |
|
* map contains more than <tt>Integer.MAX_VALUE</tt> elements, returns |
832 |
|
* <tt>Integer.MAX_VALUE</tt>. |
833 |
|
* |
834 |
< |
* @return the number of key-value mappings in this map. |
834 |
> |
* @return the number of key-value mappings in this map |
835 |
|
*/ |
836 |
|
public int size() { |
707 |
– |
final Segment[] segments = this.segments; |
708 |
– |
long sum = 0; |
709 |
– |
long check = 0; |
710 |
– |
int[] mc = new int[segments.length]; |
837 |
|
// Try a few times to get accurate count. On failure due to |
838 |
|
// continuous async changes in table, resort to locking. |
839 |
< |
for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) { |
840 |
< |
check = 0; |
841 |
< |
sum = 0; |
842 |
< |
int mcsum = 0; |
843 |
< |
for (int i = 0; i < segments.length; ++i) { |
844 |
< |
sum += segments[i].count; |
845 |
< |
mcsum += mc[i] = segments[i].modCount; |
846 |
< |
} |
847 |
< |
if (mcsum != 0) { |
848 |
< |
for (int i = 0; i < segments.length; ++i) { |
849 |
< |
check += segments[i].count; |
850 |
< |
if (mc[i] != segments[i].modCount) { |
725 |
< |
check = -1; // force retry |
726 |
< |
break; |
727 |
< |
} |
839 |
> |
final Segment<K,V>[] segments = this.segments; |
840 |
> |
final int segmentCount = segments.length; |
841 |
> |
|
842 |
> |
long previousSum = 0L; |
843 |
> |
for (int retries = -1; retries < RETRIES_BEFORE_LOCK; retries++) { |
844 |
> |
long sum = 0L; // sum of modCounts |
845 |
> |
long size = 0L; |
846 |
> |
for (int i = 0; i < segmentCount; i++) { |
847 |
> |
Segment<K,V> segment = segmentAt(segments, i); |
848 |
> |
if (segment != null) { |
849 |
> |
sum += segment.modCount; |
850 |
> |
size += segment.count; |
851 |
|
} |
852 |
|
} |
853 |
< |
if (check == sum) |
854 |
< |
break; |
853 |
> |
if (sum == previousSum) |
854 |
> |
return ((size >>> 31) == 0) ? (int) size : Integer.MAX_VALUE; |
855 |
> |
previousSum = sum; |
856 |
|
} |
733 |
– |
if (check != sum) { // Resort to locking all segments |
734 |
– |
sum = 0; |
735 |
– |
for (int i = 0; i < segments.length; ++i) |
736 |
– |
segments[i].lock(); |
737 |
– |
for (int i = 0; i < segments.length; ++i) |
738 |
– |
sum += segments[i].count; |
739 |
– |
for (int i = 0; i < segments.length; ++i) |
740 |
– |
segments[i].unlock(); |
741 |
– |
} |
742 |
– |
if (sum > Integer.MAX_VALUE) |
743 |
– |
return Integer.MAX_VALUE; |
744 |
– |
else |
745 |
– |
return (int)sum; |
746 |
– |
} |
857 |
|
|
858 |
+ |
long size = 0L; |
859 |
+ |
for (int i = 0; i < segmentCount; i++) { |
860 |
+ |
Segment<K,V> segment = ensureSegment(i); |
861 |
+ |
segment.lock(); |
862 |
+ |
size += segment.count; |
863 |
+ |
} |
864 |
+ |
for (int i = 0; i < segmentCount; i++) |
865 |
+ |
segments[i].unlock(); |
866 |
+ |
return ((size >>> 31) == 0) ? (int) size : Integer.MAX_VALUE; |
867 |
+ |
} |
868 |
|
|
869 |
|
/** |
870 |
< |
* Returns the value to which the specified key is mapped in this table. |
871 |
< |
* |
872 |
< |
* @param key a key in the table. |
873 |
< |
* @return the value to which the key is mapped in this table; |
874 |
< |
* <tt>null</tt> if the key is not mapped to any value in |
875 |
< |
* this table. |
876 |
< |
* @throws NullPointerException if the key is |
877 |
< |
* <tt>null</tt>. |
870 |
> |
* Returns the value to which the specified key is mapped, |
871 |
> |
* or {@code null} if this map contains no mapping for the key. |
872 |
> |
* |
873 |
> |
* <p>More formally, if this map contains a mapping from a key |
874 |
> |
* {@code k} to a value {@code v} such that {@code key.equals(k)}, |
875 |
> |
* then this method returns {@code v}; otherwise it returns |
876 |
> |
* {@code null}. (There can be at most one such mapping.) |
877 |
> |
* |
878 |
> |
* @throws NullPointerException if the specified key is null |
879 |
|
*/ |
880 |
+ |
@SuppressWarnings("unchecked") |
881 |
|
public V get(Object key) { |
882 |
< |
int hash = hash(key); // throws NullPointerException if key null |
883 |
< |
return segmentFor(hash).get(key, hash); |
882 |
> |
Segment<K,V> s; // manually integrate access methods to reduce overhead |
883 |
> |
HashEntry<K,V>[] tab; |
884 |
> |
int h = hash(key.hashCode()); |
885 |
> |
long u = (((h >>> segmentShift) & segmentMask) << SSHIFT) + SBASE; |
886 |
> |
if ((s = (Segment<K,V>)UNSAFE.getObjectVolatile(segments, u)) != null && |
887 |
> |
(tab = s.table) != null) { |
888 |
> |
for (HashEntry<K,V> e = (HashEntry<K,V>) UNSAFE.getObjectVolatile |
889 |
> |
(tab, ((long)(((tab.length - 1) & h)) << TSHIFT) + TBASE); |
890 |
> |
e != null; e = e.next) { |
891 |
> |
K k; |
892 |
> |
if ((k = e.key) == key || (e.hash == h && key.equals(k))) |
893 |
> |
return e.value; |
894 |
> |
} |
895 |
> |
} |
896 |
> |
return null; |
897 |
|
} |
898 |
|
|
899 |
|
/** |
900 |
|
* Tests if the specified object is a key in this table. |
901 |
|
* |
902 |
< |
* @param key possible key. |
903 |
< |
* @return <tt>true</tt> if and only if the specified object |
904 |
< |
* is a key in this table, as determined by the |
905 |
< |
* <tt>equals</tt> method; <tt>false</tt> otherwise. |
906 |
< |
* @throws NullPointerException if the key is |
772 |
< |
* <tt>null</tt>. |
902 |
> |
* @param key possible key |
903 |
> |
* @return <tt>true</tt> if and only if the specified object |
904 |
> |
* is a key in this table, as determined by the |
905 |
> |
* <tt>equals</tt> method; <tt>false</tt> otherwise. |
906 |
> |
* @throws NullPointerException if the specified key is null |
907 |
|
*/ |
908 |
+ |
@SuppressWarnings("unchecked") |
909 |
|
public boolean containsKey(Object key) { |
910 |
< |
int hash = hash(key); // throws NullPointerException if key null |
911 |
< |
return segmentFor(hash).containsKey(key, hash); |
910 |
> |
Segment<K,V> s; // same as get() except no need for volatile value read |
911 |
> |
HashEntry<K,V>[] tab; |
912 |
> |
int h = hash(key.hashCode()); |
913 |
> |
long u = (((h >>> segmentShift) & segmentMask) << SSHIFT) + SBASE; |
914 |
> |
if ((s = (Segment<K,V>)UNSAFE.getObjectVolatile(segments, u)) != null && |
915 |
> |
(tab = s.table) != null) { |
916 |
> |
for (HashEntry<K,V> e = (HashEntry<K,V>) UNSAFE.getObjectVolatile |
917 |
> |
(tab, ((long)(((tab.length - 1) & h)) << TSHIFT) + TBASE); |
918 |
> |
e != null; e = e.next) { |
919 |
> |
K k; |
920 |
> |
if ((k = e.key) == key || (e.hash == h && key.equals(k))) |
921 |
> |
return true; |
922 |
> |
} |
923 |
> |
} |
924 |
> |
return false; |
925 |
|
} |
926 |
|
|
927 |
|
/** |
930 |
|
* traversal of the hash table, and so is much slower than |
931 |
|
* method <tt>containsKey</tt>. |
932 |
|
* |
933 |
< |
* @param value value whose presence in this map is to be tested. |
933 |
> |
* @param value value whose presence in this map is to be tested |
934 |
|
* @return <tt>true</tt> if this map maps one or more keys to the |
935 |
< |
* specified value. |
936 |
< |
* @throws NullPointerException if the value is <tt>null</tt>. |
935 |
> |
* specified value |
936 |
> |
* @throws NullPointerException if the specified value is null |
937 |
|
*/ |
938 |
|
public boolean containsValue(Object value) { |
939 |
+ |
// Same idea as size() |
940 |
|
if (value == null) |
941 |
|
throw new NullPointerException(); |
942 |
< |
|
943 |
< |
// See explanation of modCount use above |
944 |
< |
|
796 |
< |
final Segment[] segments = this.segments; |
797 |
< |
int[] mc = new int[segments.length]; |
798 |
< |
|
799 |
< |
// Try a few times without locking |
800 |
< |
for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) { |
801 |
< |
int sum = 0; |
802 |
< |
int mcsum = 0; |
803 |
< |
for (int i = 0; i < segments.length; ++i) { |
804 |
< |
int c = segments[i].count; |
805 |
< |
mcsum += mc[i] = segments[i].modCount; |
806 |
< |
if (segments[i].containsValue(value)) |
807 |
< |
return true; |
808 |
< |
} |
809 |
< |
boolean cleanSweep = true; |
810 |
< |
if (mcsum != 0) { |
811 |
< |
for (int i = 0; i < segments.length; ++i) { |
812 |
< |
int c = segments[i].count; |
813 |
< |
if (mc[i] != segments[i].modCount) { |
814 |
< |
cleanSweep = false; |
815 |
< |
break; |
816 |
< |
} |
817 |
< |
} |
818 |
< |
} |
819 |
< |
if (cleanSweep) |
820 |
< |
return false; |
821 |
< |
} |
822 |
< |
// Resort to locking all segments |
823 |
< |
for (int i = 0; i < segments.length; ++i) |
824 |
< |
segments[i].lock(); |
825 |
< |
boolean found = false; |
942 |
> |
final Segment<K,V>[] segments = this.segments; |
943 |
> |
long previousSum = 0L; |
944 |
> |
int lockCount = 0; |
945 |
|
try { |
946 |
< |
for (int i = 0; i < segments.length; ++i) { |
947 |
< |
if (segments[i].containsValue(value)) { |
948 |
< |
found = true; |
949 |
< |
break; |
946 |
> |
for (int retries = -1; ; retries++) { |
947 |
> |
long sum = 0L; // sum of modCounts |
948 |
> |
for (int j = 0; j < segments.length; j++) { |
949 |
> |
Segment<K,V> segment; |
950 |
> |
if (retries == RETRIES_BEFORE_LOCK) { |
951 |
> |
segment = ensureSegment(j); |
952 |
> |
segment.lock(); |
953 |
> |
lockCount++; |
954 |
> |
} else { |
955 |
> |
segment = segmentAt(segments, j); |
956 |
> |
if (segment == null) |
957 |
> |
continue; |
958 |
> |
} |
959 |
> |
HashEntry<K,V>[] tab = segment.table; |
960 |
> |
if (tab != null) { |
961 |
> |
for (int i = 0 ; i < tab.length; i++) { |
962 |
> |
HashEntry<K,V> e; |
963 |
> |
for (e = entryAt(tab, i); e != null; e = e.next) { |
964 |
> |
V v = e.value; |
965 |
> |
if (v != null && value.equals(v)) |
966 |
> |
return true; |
967 |
> |
} |
968 |
> |
} |
969 |
> |
sum += segment.modCount; |
970 |
> |
} |
971 |
|
} |
972 |
+ |
if ((retries >= 0 && sum == previousSum) || lockCount > 0) |
973 |
+ |
return false; |
974 |
+ |
previousSum = sum; |
975 |
|
} |
976 |
|
} finally { |
977 |
< |
for (int i = 0; i < segments.length; ++i) |
978 |
< |
segments[i].unlock(); |
977 |
> |
for (int j = 0; j < lockCount; j++) |
978 |
> |
segments[j].unlock(); |
979 |
|
} |
837 |
– |
return found; |
980 |
|
} |
981 |
|
|
982 |
|
/** |
983 |
|
* Legacy method testing if some key maps into the specified value |
984 |
|
* in this table. This method is identical in functionality to |
985 |
< |
* {@link #containsValue}, and exists solely to ensure |
985 |
> |
* {@link #containsValue}, and exists solely to ensure |
986 |
|
* full compatibility with class {@link java.util.Hashtable}, |
987 |
|
* which supported this method prior to introduction of the |
988 |
|
* Java Collections framework. |
989 |
< |
|
990 |
< |
* @param value a value to search for. |
991 |
< |
* @return <tt>true</tt> if and only if some key maps to the |
992 |
< |
* <tt>value</tt> argument in this table as |
993 |
< |
* determined by the <tt>equals</tt> method; |
994 |
< |
* <tt>false</tt> otherwise. |
995 |
< |
* @throws NullPointerException if the value is <tt>null</tt>. |
989 |
> |
* |
990 |
> |
* @param value a value to search for |
991 |
> |
* @return <tt>true</tt> if and only if some key maps to the |
992 |
> |
* <tt>value</tt> argument in this table as |
993 |
> |
* determined by the <tt>equals</tt> method; |
994 |
> |
* <tt>false</tt> otherwise |
995 |
> |
* @throws NullPointerException if the specified value is null |
996 |
|
*/ |
997 |
|
public boolean contains(Object value) { |
998 |
|
return containsValue(value); |
999 |
|
} |
1000 |
|
|
1001 |
|
/** |
1002 |
< |
* Maps the specified <tt>key</tt> to the specified |
1003 |
< |
* <tt>value</tt> in this table. Neither the key nor the |
862 |
< |
* value can be <tt>null</tt>. |
1002 |
> |
* Maps the specified key to the specified value in this table. |
1003 |
> |
* Neither the key nor the value can be null. |
1004 |
|
* |
1005 |
|
* <p> The value can be retrieved by calling the <tt>get</tt> method |
1006 |
|
* with a key that is equal to the original key. |
1007 |
|
* |
1008 |
< |
* @param key the table key. |
1009 |
< |
* @param value the value. |
1010 |
< |
* @return the previous value of the specified key in this table, |
1011 |
< |
* or <tt>null</tt> if it did not have one. |
1012 |
< |
* @throws NullPointerException if the key or value is |
872 |
< |
* <tt>null</tt>. |
1008 |
> |
* @param key key with which the specified value is to be associated |
1009 |
> |
* @param value value to be associated with the specified key |
1010 |
> |
* @return the previous value associated with <tt>key</tt>, or |
1011 |
> |
* <tt>null</tt> if there was no mapping for <tt>key</tt> |
1012 |
> |
* @throws NullPointerException if the specified key or value is null |
1013 |
|
*/ |
1014 |
+ |
@SuppressWarnings("unchecked") |
1015 |
|
public V put(K key, V value) { |
1016 |
+ |
Segment<K,V> s; |
1017 |
|
if (value == null) |
1018 |
|
throw new NullPointerException(); |
1019 |
< |
int hash = hash(key); |
1020 |
< |
return segmentFor(hash).put(key, hash, value, false); |
1019 |
> |
int hash = hash(key.hashCode()); |
1020 |
> |
int j = (hash >>> segmentShift) & segmentMask; |
1021 |
> |
if ((s = (Segment<K,V>)UNSAFE.getObject // nonvolatile; recheck |
1022 |
> |
(segments, (j << SSHIFT) + SBASE)) == null) // in ensureSegment |
1023 |
> |
s = ensureSegment(j); |
1024 |
> |
return s.put(key, hash, value, false); |
1025 |
|
} |
1026 |
|
|
1027 |
|
/** |
1028 |
< |
* If the specified key is not already associated |
1029 |
< |
* with a value, associate it with the given value. |
1030 |
< |
* This is equivalent to |
1031 |
< |
* <pre> |
1032 |
< |
* if (!map.containsKey(key)) |
887 |
< |
* return map.put(key, value); |
888 |
< |
* else |
889 |
< |
* return map.get(key);</pre> |
890 |
< |
* except that the action is performed atomically. |
891 |
< |
* @param key key with which the specified value is to be associated. |
892 |
< |
* @param value value to be associated with the specified key. |
893 |
< |
* @return previous value associated with specified key, or <tt>null</tt> |
894 |
< |
* if there was no mapping for key. |
895 |
< |
* @throws NullPointerException if the specified key or value is |
896 |
< |
* <tt>null</tt>. |
1028 |
> |
* {@inheritDoc} |
1029 |
> |
* |
1030 |
> |
* @return the previous value associated with the specified key, |
1031 |
> |
* or <tt>null</tt> if there was no mapping for the key |
1032 |
> |
* @throws NullPointerException if the specified key or value is null |
1033 |
|
*/ |
1034 |
+ |
@SuppressWarnings("unchecked") |
1035 |
|
public V putIfAbsent(K key, V value) { |
1036 |
+ |
Segment<K,V> s; |
1037 |
|
if (value == null) |
1038 |
|
throw new NullPointerException(); |
1039 |
< |
int hash = hash(key); |
1040 |
< |
return segmentFor(hash).put(key, hash, value, true); |
1039 |
> |
int hash = hash(key.hashCode()); |
1040 |
> |
int j = (hash >>> segmentShift) & segmentMask; |
1041 |
> |
if ((s = (Segment<K,V>)UNSAFE.getObject |
1042 |
> |
(segments, (j << SSHIFT) + SBASE)) == null) |
1043 |
> |
s = ensureSegment(j); |
1044 |
> |
return s.put(key, hash, value, true); |
1045 |
|
} |
1046 |
|
|
905 |
– |
|
1047 |
|
/** |
1048 |
|
* Copies all of the mappings from the specified map to this one. |
908 |
– |
* |
1049 |
|
* These mappings replace any mappings that this map had for any of the |
1050 |
< |
* keys currently in the specified Map. |
1050 |
> |
* keys currently in the specified map. |
1051 |
|
* |
1052 |
< |
* @param t Mappings to be stored in this map. |
1052 |
> |
* @param m mappings to be stored in this map |
1053 |
|
*/ |
1054 |
< |
public void putAll(Map<? extends K, ? extends V> t) { |
1055 |
< |
for (Iterator<? extends Map.Entry<? extends K, ? extends V>> it = (Iterator<? extends Map.Entry<? extends K, ? extends V>>) t.entrySet().iterator(); it.hasNext(); ) { |
916 |
< |
Entry<? extends K, ? extends V> e = it.next(); |
1054 |
> |
public void putAll(Map<? extends K, ? extends V> m) { |
1055 |
> |
for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) |
1056 |
|
put(e.getKey(), e.getValue()); |
918 |
– |
} |
1057 |
|
} |
1058 |
|
|
1059 |
|
/** |
1060 |
< |
* Removes the key (and its corresponding value) from this |
1061 |
< |
* table. This method does nothing if the key is not in the table. |
1060 |
> |
* Removes the key (and its corresponding value) from this map. |
1061 |
> |
* This method does nothing if the key is not in the map. |
1062 |
|
* |
1063 |
< |
* @param key the key that needs to be removed. |
1064 |
< |
* @return the value to which the key had been mapped in this table, |
1065 |
< |
* or <tt>null</tt> if the key did not have a mapping. |
1066 |
< |
* @throws NullPointerException if the key is |
929 |
< |
* <tt>null</tt>. |
1063 |
> |
* @param key the key that needs to be removed |
1064 |
> |
* @return the previous value associated with <tt>key</tt>, or |
1065 |
> |
* <tt>null</tt> if there was no mapping for <tt>key</tt> |
1066 |
> |
* @throws NullPointerException if the specified key is null |
1067 |
|
*/ |
1068 |
|
public V remove(Object key) { |
1069 |
< |
int hash = hash(key); |
1070 |
< |
return segmentFor(hash).remove(key, hash, null); |
1069 |
> |
int hash = hash(key.hashCode()); |
1070 |
> |
Segment<K,V> s = segmentForHash(hash); |
1071 |
> |
return s == null ? null : s.remove(key, hash, null); |
1072 |
|
} |
1073 |
|
|
1074 |
|
/** |
1075 |
< |
* Remove entry for key only if currently mapped to given value. |
1076 |
< |
* Acts as |
1077 |
< |
* <pre> |
940 |
< |
* if (map.get(key).equals(value)) { |
941 |
< |
* map.remove(key); |
942 |
< |
* return true; |
943 |
< |
* } else return false;</pre> |
944 |
< |
* except that the action is performed atomically. |
945 |
< |
* @param key key with which the specified value is associated. |
946 |
< |
* @param value value associated with the specified key. |
947 |
< |
* @return true if the value was removed |
948 |
< |
* @throws NullPointerException if the specified key is |
949 |
< |
* <tt>null</tt>. |
1075 |
> |
* {@inheritDoc} |
1076 |
> |
* |
1077 |
> |
* @throws NullPointerException if the specified key is null |
1078 |
|
*/ |
1079 |
|
public boolean remove(Object key, Object value) { |
1080 |
< |
int hash = hash(key); |
1081 |
< |
return segmentFor(hash).remove(key, hash, value) != null; |
1080 |
> |
int hash = hash(key.hashCode()); |
1081 |
> |
Segment<K,V> s; |
1082 |
> |
return value != null && (s = segmentForHash(hash)) != null && |
1083 |
> |
s.remove(key, hash, value) != null; |
1084 |
|
} |
1085 |
|
|
956 |
– |
|
1086 |
|
/** |
1087 |
< |
* Replaces entry for key only if currently mapped to given value. |
1088 |
< |
* Acts as |
1089 |
< |
* <pre> |
961 |
< |
* if (map.get(key).equals(oldValue)) { |
962 |
< |
* map.put(key, newValue); |
963 |
< |
* return true; |
964 |
< |
* } else return false;</pre> |
965 |
< |
* except that the action is performed atomically. |
966 |
< |
* @param key key with which the specified value is associated. |
967 |
< |
* @param oldValue value expected to be associated with the specified key. |
968 |
< |
* @param newValue value to be associated with the specified key. |
969 |
< |
* @return true if the value was replaced |
970 |
< |
* @throws NullPointerException if the specified key or values are |
971 |
< |
* <tt>null</tt>. |
1087 |
> |
* {@inheritDoc} |
1088 |
> |
* |
1089 |
> |
* @throws NullPointerException if any of the arguments are null |
1090 |
|
*/ |
1091 |
|
public boolean replace(K key, V oldValue, V newValue) { |
1092 |
+ |
int hash = hash(key.hashCode()); |
1093 |
|
if (oldValue == null || newValue == null) |
1094 |
|
throw new NullPointerException(); |
1095 |
< |
int hash = hash(key); |
1096 |
< |
return segmentFor(hash).replace(key, hash, oldValue, newValue); |
1095 |
> |
Segment<K,V> s = segmentForHash(hash); |
1096 |
> |
return s != null && s.replace(key, hash, oldValue, newValue); |
1097 |
|
} |
1098 |
|
|
1099 |
|
/** |
1100 |
< |
* Replaces entry for key only if currently mapped to some value. |
1101 |
< |
* Acts as |
1102 |
< |
* <pre> |
1103 |
< |
* if (map.containsKey(key)) { |
1104 |
< |
* return map.put(key, value); |
986 |
< |
* } else return null;</pre> |
987 |
< |
* except that the action is performed atomically. |
988 |
< |
* @param key key with which the specified value is associated. |
989 |
< |
* @param value value to be associated with the specified key. |
990 |
< |
* @return previous value associated with specified key, or <tt>null</tt> |
991 |
< |
* if there was no mapping for key. |
992 |
< |
* @throws NullPointerException if the specified key or value is |
993 |
< |
* <tt>null</tt>. |
1100 |
> |
* {@inheritDoc} |
1101 |
> |
* |
1102 |
> |
* @return the previous value associated with the specified key, |
1103 |
> |
* or <tt>null</tt> if there was no mapping for the key |
1104 |
> |
* @throws NullPointerException if the specified key or value is null |
1105 |
|
*/ |
1106 |
|
public V replace(K key, V value) { |
1107 |
+ |
int hash = hash(key.hashCode()); |
1108 |
|
if (value == null) |
1109 |
|
throw new NullPointerException(); |
1110 |
< |
int hash = hash(key); |
1111 |
< |
return segmentFor(hash).replace(key, hash, value); |
1110 |
> |
Segment<K,V> s = segmentForHash(hash); |
1111 |
> |
return s == null ? null : s.replace(key, hash, value); |
1112 |
|
} |
1113 |
|
|
1002 |
– |
|
1114 |
|
/** |
1115 |
< |
* Removes all mappings from this map. |
1115 |
> |
* Removes all of the mappings from this map. |
1116 |
|
*/ |
1117 |
|
public void clear() { |
1118 |
< |
for (int i = 0; i < segments.length; ++i) |
1119 |
< |
segments[i].clear(); |
1118 |
> |
final Segment<K,V>[] segments = this.segments; |
1119 |
> |
for (int j = 0; j < segments.length; ++j) { |
1120 |
> |
Segment<K,V> s = segmentAt(segments, j); |
1121 |
> |
if (s != null) |
1122 |
> |
s.clear(); |
1123 |
> |
} |
1124 |
|
} |
1125 |
|
|
1126 |
|
/** |
1127 |
< |
* Returns a set view of the keys contained in this map. The set is |
1128 |
< |
* backed by the map, so changes to the map are reflected in the set, and |
1129 |
< |
* vice-versa. The set supports element removal, which removes the |
1130 |
< |
* corresponding mapping from this map, via the <tt>Iterator.remove</tt>, |
1131 |
< |
* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and |
1132 |
< |
* <tt>clear</tt> operations. It does not support the <tt>add</tt> or |
1127 |
> |
* Returns a {@link Set} view of the keys contained in this map. |
1128 |
> |
* The set is backed by the map, so changes to the map are |
1129 |
> |
* reflected in the set, and vice-versa. The set supports element |
1130 |
> |
* removal, which removes the corresponding mapping from this map, |
1131 |
> |
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, |
1132 |
> |
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> |
1133 |
> |
* operations. It does not support the <tt>add</tt> or |
1134 |
|
* <tt>addAll</tt> operations. |
1135 |
< |
* The view's returned <tt>iterator</tt> is a "weakly consistent" iterator that |
1136 |
< |
* will never throw {@link java.util.ConcurrentModificationException}, |
1135 |
> |
* |
1136 |
> |
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator |
1137 |
> |
* that will never throw {@link ConcurrentModificationException}, |
1138 |
|
* and guarantees to traverse elements as they existed upon |
1139 |
|
* construction of the iterator, and may (but is not guaranteed to) |
1140 |
|
* reflect any modifications subsequent to construction. |
1024 |
– |
* |
1025 |
– |
* @return a set view of the keys contained in this map. |
1141 |
|
*/ |
1142 |
|
public Set<K> keySet() { |
1143 |
|
Set<K> ks = keySet; |
1144 |
|
return (ks != null) ? ks : (keySet = new KeySet()); |
1145 |
|
} |
1146 |
|
|
1032 |
– |
|
1147 |
|
/** |
1148 |
< |
* Returns a collection view of the values contained in this map. The |
1149 |
< |
* collection is backed by the map, so changes to the map are reflected in |
1150 |
< |
* the collection, and vice-versa. The collection supports element |
1151 |
< |
* removal, which removes the corresponding mapping from this map, via the |
1152 |
< |
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>, |
1153 |
< |
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations. |
1154 |
< |
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations. |
1155 |
< |
* The view's returned <tt>iterator</tt> is a "weakly consistent" iterator that |
1156 |
< |
* will never throw {@link java.util.ConcurrentModificationException}, |
1148 |
> |
* Returns a {@link Collection} view of the values contained in this map. |
1149 |
> |
* The collection is backed by the map, so changes to the map are |
1150 |
> |
* reflected in the collection, and vice-versa. The collection |
1151 |
> |
* supports element removal, which removes the corresponding |
1152 |
> |
* mapping from this map, via the <tt>Iterator.remove</tt>, |
1153 |
> |
* <tt>Collection.remove</tt>, <tt>removeAll</tt>, |
1154 |
> |
* <tt>retainAll</tt>, and <tt>clear</tt> operations. It does not |
1155 |
> |
* support the <tt>add</tt> or <tt>addAll</tt> operations. |
1156 |
> |
* |
1157 |
> |
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator |
1158 |
> |
* that will never throw {@link ConcurrentModificationException}, |
1159 |
|
* and guarantees to traverse elements as they existed upon |
1160 |
|
* construction of the iterator, and may (but is not guaranteed to) |
1161 |
|
* reflect any modifications subsequent to construction. |
1046 |
– |
* |
1047 |
– |
* @return a collection view of the values contained in this map. |
1162 |
|
*/ |
1163 |
|
public Collection<V> values() { |
1164 |
|
Collection<V> vs = values; |
1165 |
|
return (vs != null) ? vs : (values = new Values()); |
1166 |
|
} |
1167 |
|
|
1054 |
– |
|
1168 |
|
/** |
1169 |
< |
* Returns a collection view of the mappings contained in this map. Each |
1170 |
< |
* element in the returned collection is a <tt>Map.Entry</tt>. The |
1171 |
< |
* collection is backed by the map, so changes to the map are reflected in |
1172 |
< |
* the collection, and vice-versa. The collection supports element |
1173 |
< |
* removal, which removes the corresponding mapping from the map, via the |
1174 |
< |
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>, |
1175 |
< |
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations. |
1176 |
< |
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations. |
1177 |
< |
* The view's returned <tt>iterator</tt> is a "weakly consistent" iterator that |
1178 |
< |
* will never throw {@link java.util.ConcurrentModificationException}, |
1169 |
> |
* Returns a {@link Set} view of the mappings contained in this map. |
1170 |
> |
* The set is backed by the map, so changes to the map are |
1171 |
> |
* reflected in the set, and vice-versa. The set supports element |
1172 |
> |
* removal, which removes the corresponding mapping from the map, |
1173 |
> |
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, |
1174 |
> |
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> |
1175 |
> |
* operations. It does not support the <tt>add</tt> or |
1176 |
> |
* <tt>addAll</tt> operations. |
1177 |
> |
* |
1178 |
> |
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator |
1179 |
> |
* that will never throw {@link ConcurrentModificationException}, |
1180 |
|
* and guarantees to traverse elements as they existed upon |
1181 |
|
* construction of the iterator, and may (but is not guaranteed to) |
1182 |
|
* reflect any modifications subsequent to construction. |
1069 |
– |
* |
1070 |
– |
* @return a collection view of the mappings contained in this map. |
1183 |
|
*/ |
1184 |
|
public Set<Map.Entry<K,V>> entrySet() { |
1185 |
|
Set<Map.Entry<K,V>> es = entrySet; |
1186 |
< |
return (es != null) ? es : (entrySet = (Set<Map.Entry<K,V>>) (Set) new EntrySet()); |
1186 |
> |
return (es != null) ? es : (entrySet = new EntrySet()); |
1187 |
|
} |
1188 |
|
|
1077 |
– |
|
1189 |
|
/** |
1190 |
|
* Returns an enumeration of the keys in this table. |
1191 |
|
* |
1192 |
< |
* @return an enumeration of the keys in this table. |
1193 |
< |
* @see #keySet |
1192 |
> |
* @return an enumeration of the keys in this table |
1193 |
> |
* @see #keySet() |
1194 |
|
*/ |
1195 |
|
public Enumeration<K> keys() { |
1196 |
|
return new KeyIterator(); |
1199 |
|
/** |
1200 |
|
* Returns an enumeration of the values in this table. |
1201 |
|
* |
1202 |
< |
* @return an enumeration of the values in this table. |
1203 |
< |
* @see #values |
1202 |
> |
* @return an enumeration of the values in this table |
1203 |
> |
* @see #values() |
1204 |
|
*/ |
1205 |
|
public Enumeration<V> elements() { |
1206 |
|
return new ValueIterator(); |
1211 |
|
abstract class HashIterator { |
1212 |
|
int nextSegmentIndex; |
1213 |
|
int nextTableIndex; |
1214 |
< |
HashEntry[] currentTable; |
1214 |
> |
HashEntry<K,V>[] currentTable; |
1215 |
|
HashEntry<K, V> nextEntry; |
1216 |
|
HashEntry<K, V> lastReturned; |
1217 |
|
|
1221 |
|
advance(); |
1222 |
|
} |
1223 |
|
|
1224 |
< |
public boolean hasMoreElements() { return hasNext(); } |
1225 |
< |
|
1224 |
> |
/** |
1225 |
> |
* Sets nextEntry to first node of next non-empty table |
1226 |
> |
* (in backwards order, to simplify checks). |
1227 |
> |
*/ |
1228 |
|
final void advance() { |
1229 |
< |
if (nextEntry != null && (nextEntry = nextEntry.next) != null) |
1230 |
< |
return; |
1231 |
< |
|
1232 |
< |
while (nextTableIndex >= 0) { |
1233 |
< |
if ( (nextEntry = (HashEntry<K,V>)currentTable[nextTableIndex--]) != null) |
1234 |
< |
return; |
1235 |
< |
} |
1236 |
< |
|
1237 |
< |
while (nextSegmentIndex >= 0) { |
1238 |
< |
Segment<K,V> seg = (Segment<K,V>)segments[nextSegmentIndex--]; |
1126 |
< |
if (seg.count != 0) { |
1127 |
< |
currentTable = seg.table; |
1128 |
< |
for (int j = currentTable.length - 1; j >= 0; --j) { |
1129 |
< |
if ( (nextEntry = (HashEntry<K,V>)currentTable[j]) != null) { |
1130 |
< |
nextTableIndex = j - 1; |
1131 |
< |
return; |
1132 |
< |
} |
1133 |
< |
} |
1229 |
> |
for (;;) { |
1230 |
> |
if (nextTableIndex >= 0) { |
1231 |
> |
if ((nextEntry = entryAt(currentTable, |
1232 |
> |
nextTableIndex--)) != null) |
1233 |
> |
break; |
1234 |
> |
} |
1235 |
> |
else if (nextSegmentIndex >= 0) { |
1236 |
> |
Segment<K,V> seg = segmentAt(segments, nextSegmentIndex--); |
1237 |
> |
if (seg != null && (currentTable = seg.table) != null) |
1238 |
> |
nextTableIndex = currentTable.length - 1; |
1239 |
|
} |
1240 |
+ |
else |
1241 |
+ |
break; |
1242 |
|
} |
1243 |
|
} |
1244 |
|
|
1245 |
< |
public boolean hasNext() { return nextEntry != null; } |
1246 |
< |
|
1247 |
< |
HashEntry<K,V> nextEntry() { |
1141 |
< |
if (nextEntry == null) |
1245 |
> |
final HashEntry<K,V> nextEntry() { |
1246 |
> |
HashEntry<K,V> e = nextEntry; |
1247 |
> |
if (e == null) |
1248 |
|
throw new NoSuchElementException(); |
1249 |
< |
lastReturned = nextEntry; |
1250 |
< |
advance(); |
1251 |
< |
return lastReturned; |
1249 |
> |
lastReturned = e; // cannot assign until after null check |
1250 |
> |
if ((nextEntry = e.next) == null) |
1251 |
> |
advance(); |
1252 |
> |
return e; |
1253 |
|
} |
1254 |
|
|
1255 |
< |
public void remove() { |
1255 |
> |
public final boolean hasNext() { return nextEntry != null; } |
1256 |
> |
public final boolean hasMoreElements() { return nextEntry != null; } |
1257 |
> |
|
1258 |
> |
public final void remove() { |
1259 |
|
if (lastReturned == null) |
1260 |
|
throw new IllegalStateException(); |
1261 |
|
ConcurrentHashMap.this.remove(lastReturned.key); |
1263 |
|
} |
1264 |
|
} |
1265 |
|
|
1266 |
< |
final class KeyIterator extends HashIterator implements Iterator<K>, Enumeration<K> { |
1267 |
< |
public K next() { return super.nextEntry().key; } |
1268 |
< |
public K nextElement() { return super.nextEntry().key; } |
1266 |
> |
final class KeyIterator |
1267 |
> |
extends HashIterator |
1268 |
> |
implements Iterator<K>, Enumeration<K> |
1269 |
> |
{ |
1270 |
> |
public final K next() { return super.nextEntry().key; } |
1271 |
> |
public final K nextElement() { return super.nextEntry().key; } |
1272 |
|
} |
1273 |
|
|
1274 |
< |
final class ValueIterator extends HashIterator implements Iterator<V>, Enumeration<V> { |
1275 |
< |
public V next() { return super.nextEntry().value; } |
1276 |
< |
public V nextElement() { return super.nextEntry().value; } |
1274 |
> |
final class ValueIterator |
1275 |
> |
extends HashIterator |
1276 |
> |
implements Iterator<V>, Enumeration<V> |
1277 |
> |
{ |
1278 |
> |
public final V next() { return super.nextEntry().value; } |
1279 |
> |
public final V nextElement() { return super.nextEntry().value; } |
1280 |
|
} |
1281 |
|
|
1166 |
– |
|
1167 |
– |
|
1282 |
|
/** |
1283 |
< |
* Entry iterator. Exported Entry objects must write-through |
1284 |
< |
* changes in setValue, even if the nodes have been cloned. So we |
1171 |
< |
* cannot return internal HashEntry objects. Instead, the iterator |
1172 |
< |
* itself acts as a forwarding pseudo-entry. |
1283 |
> |
* Custom Entry class used by EntryIterator.next(), that relays |
1284 |
> |
* setValue changes to the underlying map. |
1285 |
|
*/ |
1286 |
< |
final class EntryIterator extends HashIterator implements Map.Entry<K,V>, Iterator<Entry<K,V>> { |
1287 |
< |
public Map.Entry<K,V> next() { |
1288 |
< |
nextEntry(); |
1289 |
< |
return this; |
1178 |
< |
} |
1179 |
< |
|
1180 |
< |
public K getKey() { |
1181 |
< |
if (lastReturned == null) |
1182 |
< |
throw new IllegalStateException("Entry was removed"); |
1183 |
< |
return lastReturned.key; |
1184 |
< |
} |
1286 |
> |
final class WriteThroughEntry |
1287 |
> |
extends AbstractMap.SimpleEntry<K,V> |
1288 |
> |
{ |
1289 |
> |
static final long serialVersionUID = 7249069246763182397L; |
1290 |
|
|
1291 |
< |
public V getValue() { |
1292 |
< |
if (lastReturned == null) |
1188 |
< |
throw new IllegalStateException("Entry was removed"); |
1189 |
< |
return ConcurrentHashMap.this.get(lastReturned.key); |
1291 |
> |
WriteThroughEntry(K k, V v) { |
1292 |
> |
super(k,v); |
1293 |
|
} |
1294 |
|
|
1295 |
+ |
/** |
1296 |
+ |
* Sets our entry's value and writes through to the map. The |
1297 |
+ |
* value to return is somewhat arbitrary here. Since a |
1298 |
+ |
* WriteThroughEntry does not necessarily track asynchronous |
1299 |
+ |
* changes, the most recent "previous" value could be |
1300 |
+ |
* different from what we return (or could even have been |
1301 |
+ |
* removed in which case the put will re-establish). We do not |
1302 |
+ |
* and cannot guarantee more. |
1303 |
+ |
*/ |
1304 |
|
public V setValue(V value) { |
1305 |
< |
if (lastReturned == null) |
1306 |
< |
throw new IllegalStateException("Entry was removed"); |
1307 |
< |
return ConcurrentHashMap.this.put(lastReturned.key, value); |
1308 |
< |
} |
1197 |
< |
|
1198 |
< |
public boolean equals(Object o) { |
1199 |
< |
// If not acting as entry, just use default. |
1200 |
< |
if (lastReturned == null) |
1201 |
< |
return super.equals(o); |
1202 |
< |
if (!(o instanceof Map.Entry)) |
1203 |
< |
return false; |
1204 |
< |
Map.Entry e = (Map.Entry)o; |
1205 |
< |
return eq(getKey(), e.getKey()) && eq(getValue(), e.getValue()); |
1206 |
< |
} |
1207 |
< |
|
1208 |
< |
public int hashCode() { |
1209 |
< |
// If not acting as entry, just use default. |
1210 |
< |
if (lastReturned == null) |
1211 |
< |
return super.hashCode(); |
1212 |
< |
|
1213 |
< |
Object k = getKey(); |
1214 |
< |
Object v = getValue(); |
1215 |
< |
return ((k == null) ? 0 : k.hashCode()) ^ |
1216 |
< |
((v == null) ? 0 : v.hashCode()); |
1217 |
< |
} |
1218 |
< |
|
1219 |
< |
public String toString() { |
1220 |
< |
// If not acting as entry, just use default. |
1221 |
< |
if (lastReturned == null) |
1222 |
< |
return super.toString(); |
1223 |
< |
else |
1224 |
< |
return getKey() + "=" + getValue(); |
1305 |
> |
if (value == null) throw new NullPointerException(); |
1306 |
> |
V v = super.setValue(value); |
1307 |
> |
ConcurrentHashMap.this.put(getKey(), value); |
1308 |
> |
return v; |
1309 |
|
} |
1310 |
+ |
} |
1311 |
|
|
1312 |
< |
boolean eq(Object o1, Object o2) { |
1313 |
< |
return (o1 == null ? o2 == null : o1.equals(o2)); |
1312 |
> |
final class EntryIterator |
1313 |
> |
extends HashIterator |
1314 |
> |
implements Iterator<Entry<K,V>> |
1315 |
> |
{ |
1316 |
> |
public Map.Entry<K,V> next() { |
1317 |
> |
HashEntry<K,V> e = super.nextEntry(); |
1318 |
> |
return new WriteThroughEntry(e.key, e.value); |
1319 |
|
} |
1230 |
– |
|
1320 |
|
} |
1321 |
|
|
1322 |
|
final class KeySet extends AbstractSet<K> { |
1326 |
|
public int size() { |
1327 |
|
return ConcurrentHashMap.this.size(); |
1328 |
|
} |
1329 |
+ |
public boolean isEmpty() { |
1330 |
+ |
return ConcurrentHashMap.this.isEmpty(); |
1331 |
+ |
} |
1332 |
|
public boolean contains(Object o) { |
1333 |
|
return ConcurrentHashMap.this.containsKey(o); |
1334 |
|
} |
1338 |
|
public void clear() { |
1339 |
|
ConcurrentHashMap.this.clear(); |
1340 |
|
} |
1249 |
– |
public Object[] toArray() { |
1250 |
– |
Collection<K> c = new ArrayList<K>(); |
1251 |
– |
for (Iterator<K> i = iterator(); i.hasNext(); ) |
1252 |
– |
c.add(i.next()); |
1253 |
– |
return c.toArray(); |
1254 |
– |
} |
1255 |
– |
public <T> T[] toArray(T[] a) { |
1256 |
– |
Collection<K> c = new ArrayList<K>(); |
1257 |
– |
for (Iterator<K> i = iterator(); i.hasNext(); ) |
1258 |
– |
c.add(i.next()); |
1259 |
– |
return c.toArray(a); |
1260 |
– |
} |
1341 |
|
} |
1342 |
|
|
1343 |
|
final class Values extends AbstractCollection<V> { |
1347 |
|
public int size() { |
1348 |
|
return ConcurrentHashMap.this.size(); |
1349 |
|
} |
1350 |
+ |
public boolean isEmpty() { |
1351 |
+ |
return ConcurrentHashMap.this.isEmpty(); |
1352 |
+ |
} |
1353 |
|
public boolean contains(Object o) { |
1354 |
|
return ConcurrentHashMap.this.containsValue(o); |
1355 |
|
} |
1356 |
|
public void clear() { |
1357 |
|
ConcurrentHashMap.this.clear(); |
1358 |
|
} |
1276 |
– |
public Object[] toArray() { |
1277 |
– |
Collection<V> c = new ArrayList<V>(); |
1278 |
– |
for (Iterator<V> i = iterator(); i.hasNext(); ) |
1279 |
– |
c.add(i.next()); |
1280 |
– |
return c.toArray(); |
1281 |
– |
} |
1282 |
– |
public <T> T[] toArray(T[] a) { |
1283 |
– |
Collection<V> c = new ArrayList<V>(); |
1284 |
– |
for (Iterator<V> i = iterator(); i.hasNext(); ) |
1285 |
– |
c.add(i.next()); |
1286 |
– |
return c.toArray(a); |
1287 |
– |
} |
1359 |
|
} |
1360 |
|
|
1361 |
|
final class EntrySet extends AbstractSet<Map.Entry<K,V>> { |
1365 |
|
public boolean contains(Object o) { |
1366 |
|
if (!(o instanceof Map.Entry)) |
1367 |
|
return false; |
1368 |
< |
Map.Entry<K,V> e = (Map.Entry<K,V>)o; |
1368 |
> |
Map.Entry<?,?> e = (Map.Entry<?,?>)o; |
1369 |
|
V v = ConcurrentHashMap.this.get(e.getKey()); |
1370 |
|
return v != null && v.equals(e.getValue()); |
1371 |
|
} |
1372 |
|
public boolean remove(Object o) { |
1373 |
|
if (!(o instanceof Map.Entry)) |
1374 |
|
return false; |
1375 |
< |
Map.Entry<K,V> e = (Map.Entry<K,V>)o; |
1375 |
> |
Map.Entry<?,?> e = (Map.Entry<?,?>)o; |
1376 |
|
return ConcurrentHashMap.this.remove(e.getKey(), e.getValue()); |
1377 |
|
} |
1378 |
|
public int size() { |
1379 |
|
return ConcurrentHashMap.this.size(); |
1380 |
|
} |
1381 |
+ |
public boolean isEmpty() { |
1382 |
+ |
return ConcurrentHashMap.this.isEmpty(); |
1383 |
+ |
} |
1384 |
|
public void clear() { |
1385 |
|
ConcurrentHashMap.this.clear(); |
1386 |
|
} |
1313 |
– |
public Object[] toArray() { |
1314 |
– |
// Since we don't ordinarily have distinct Entry objects, we |
1315 |
– |
// must pack elements using exportable SimpleEntry |
1316 |
– |
Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>(size()); |
1317 |
– |
for (Iterator<Map.Entry<K,V>> i = iterator(); i.hasNext(); ) |
1318 |
– |
c.add(new AbstractMap.SimpleEntry<K,V>(i.next())); |
1319 |
– |
return c.toArray(); |
1320 |
– |
} |
1321 |
– |
public <T> T[] toArray(T[] a) { |
1322 |
– |
Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>(size()); |
1323 |
– |
for (Iterator<Map.Entry<K,V>> i = iterator(); i.hasNext(); ) |
1324 |
– |
c.add(new AbstractMap.SimpleEntry<K,V>(i.next())); |
1325 |
– |
return c.toArray(a); |
1326 |
– |
} |
1327 |
– |
|
1387 |
|
} |
1388 |
|
|
1389 |
|
/* ---------------- Serialization Support -------------- */ |
1390 |
|
|
1391 |
|
/** |
1392 |
< |
* Save the state of the <tt>ConcurrentHashMap</tt> |
1393 |
< |
* instance to a stream (i.e., |
1335 |
< |
* serialize it). |
1392 |
> |
* Saves the state of the <tt>ConcurrentHashMap</tt> instance to a |
1393 |
> |
* stream (i.e., serializes it). |
1394 |
|
* @param s the stream |
1395 |
|
* @serialData |
1396 |
|
* the key (Object) and value (Object) |
1397 |
|
* for each key-value mapping, followed by a null pair. |
1398 |
|
* The key-value mappings are emitted in no particular order. |
1399 |
|
*/ |
1400 |
< |
private void writeObject(java.io.ObjectOutputStream s) throws IOException { |
1400 |
> |
private void writeObject(java.io.ObjectOutputStream s) |
1401 |
> |
throws java.io.IOException { |
1402 |
> |
// force all segments for serialization compatibility |
1403 |
> |
for (int k = 0; k < segments.length; ++k) |
1404 |
> |
ensureSegment(k); |
1405 |
|
s.defaultWriteObject(); |
1406 |
|
|
1407 |
+ |
final Segment<K,V>[] segments = this.segments; |
1408 |
|
for (int k = 0; k < segments.length; ++k) { |
1409 |
< |
Segment<K,V> seg = (Segment<K,V>)segments[k]; |
1409 |
> |
Segment<K,V> seg = segmentAt(segments, k); |
1410 |
|
seg.lock(); |
1411 |
|
try { |
1412 |
< |
HashEntry[] tab = seg.table; |
1412 |
> |
HashEntry<K,V>[] tab = seg.table; |
1413 |
|
for (int i = 0; i < tab.length; ++i) { |
1414 |
< |
for (HashEntry<K,V> e = (HashEntry<K,V>)tab[i]; e != null; e = e.next) { |
1414 |
> |
HashEntry<K,V> e; |
1415 |
> |
for (e = entryAt(tab, i); e != null; e = e.next) { |
1416 |
|
s.writeObject(e.key); |
1417 |
|
s.writeObject(e.value); |
1418 |
|
} |
1426 |
|
} |
1427 |
|
|
1428 |
|
/** |
1429 |
< |
* Reconstitute the <tt>ConcurrentHashMap</tt> |
1430 |
< |
* instance from a stream (i.e., |
1367 |
< |
* deserialize it). |
1429 |
> |
* Reconstitutes the <tt>ConcurrentHashMap</tt> instance from a |
1430 |
> |
* stream (i.e., deserializes it). |
1431 |
|
* @param s the stream |
1432 |
|
*/ |
1433 |
+ |
@SuppressWarnings("unchecked") |
1434 |
|
private void readObject(java.io.ObjectInputStream s) |
1435 |
< |
throws IOException, ClassNotFoundException { |
1435 |
> |
throws java.io.IOException, ClassNotFoundException { |
1436 |
|
s.defaultReadObject(); |
1437 |
|
|
1438 |
< |
// Initialize each segment to be minimally sized, and let grow. |
1439 |
< |
for (int i = 0; i < segments.length; ++i) { |
1440 |
< |
segments[i].setTable(new HashEntry[1]); |
1438 |
> |
// Re-initialize segments to be minimally sized, and let grow. |
1439 |
> |
int cap = MIN_SEGMENT_TABLE_CAPACITY; |
1440 |
> |
final Segment<K,V>[] segments = this.segments; |
1441 |
> |
for (int k = 0; k < segments.length; ++k) { |
1442 |
> |
Segment<K,V> seg = segments[k]; |
1443 |
> |
if (seg != null) { |
1444 |
> |
seg.threshold = (int)(cap * seg.loadFactor); |
1445 |
> |
seg.table = (HashEntry<K,V>[]) new HashEntry<?,?>[cap]; |
1446 |
> |
} |
1447 |
|
} |
1448 |
|
|
1449 |
|
// Read the keys and values, and put the mappings in the table |
1455 |
|
put(key, value); |
1456 |
|
} |
1457 |
|
} |
1388 |
– |
} |
1458 |
|
|
1459 |
+ |
// Unsafe mechanics |
1460 |
+ |
private static final sun.misc.Unsafe UNSAFE; |
1461 |
+ |
private static final long SBASE; |
1462 |
+ |
private static final int SSHIFT; |
1463 |
+ |
private static final long TBASE; |
1464 |
+ |
private static final int TSHIFT; |
1465 |
+ |
|
1466 |
+ |
static { |
1467 |
+ |
int ss, ts; |
1468 |
+ |
try { |
1469 |
+ |
UNSAFE = sun.misc.Unsafe.getUnsafe(); |
1470 |
+ |
Class<?> tc = HashEntry[].class; |
1471 |
+ |
Class<?> sc = Segment[].class; |
1472 |
+ |
TBASE = UNSAFE.arrayBaseOffset(tc); |
1473 |
+ |
SBASE = UNSAFE.arrayBaseOffset(sc); |
1474 |
+ |
ts = UNSAFE.arrayIndexScale(tc); |
1475 |
+ |
ss = UNSAFE.arrayIndexScale(sc); |
1476 |
+ |
} catch (Exception e) { |
1477 |
+ |
throw new Error(e); |
1478 |
+ |
} |
1479 |
+ |
if ((ss & (ss-1)) != 0 || (ts & (ts-1)) != 0) |
1480 |
+ |
throw new Error("data type scale not a power of two"); |
1481 |
+ |
SSHIFT = 31 - Integer.numberOfLeadingZeros(ss); |
1482 |
+ |
TSHIFT = 31 - Integer.numberOfLeadingZeros(ts); |
1483 |
+ |
} |
1484 |
+ |
|
1485 |
+ |
} |