1 |
dl |
1.2 |
/* |
2 |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
dl |
1.36 |
* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
5 |
dl |
1.2 |
*/ |
6 |
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7 |
tim |
1.1 |
package java.util.concurrent; |
8 |
dl |
1.10 |
import java.util.concurrent.locks.*; |
9 |
tim |
1.1 |
import java.util.*; |
10 |
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import java.io.Serializable; |
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import java.io.IOException; |
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import java.io.ObjectInputStream; |
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import java.io.ObjectOutputStream; |
14 |
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15 |
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/** |
16 |
dl |
1.4 |
* A hash table supporting full concurrency of retrievals and |
17 |
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* adjustable expected concurrency for updates. This class obeys the |
18 |
dl |
1.22 |
* same functional specification as {@link java.util.Hashtable}, and |
19 |
dl |
1.19 |
* includes versions of methods corresponding to each method of |
20 |
dl |
1.25 |
* <tt>Hashtable</tt>. However, even though all operations are |
21 |
dl |
1.19 |
* thread-safe, retrieval operations do <em>not</em> entail locking, |
22 |
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* and there is <em>not</em> any support for locking the entire table |
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* in a way that prevents all access. This class is fully |
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* interoperable with <tt>Hashtable</tt> in programs that rely on its |
25 |
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1.4 |
* thread safety but not on its synchronization details. |
26 |
tim |
1.11 |
* |
27 |
dl |
1.25 |
* <p> Retrieval operations (including <tt>get</tt>) generally do not |
28 |
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* block, so may overlap with update operations (including |
29 |
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* <tt>put</tt> and <tt>remove</tt>). Retrievals reflect the results |
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* of the most recently <em>completed</em> update operations holding |
31 |
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* upon their onset. For aggregate operations such as <tt>putAll</tt> |
32 |
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* and <tt>clear</tt>, concurrent retrievals may reflect insertion or |
33 |
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1.4 |
* removal of only some entries. Similarly, Iterators and |
34 |
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* Enumerations return elements reflecting the state of the hash table |
35 |
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* at some point at or since the creation of the iterator/enumeration. |
36 |
jsr166 |
1.68 |
* They do <em>not</em> throw {@link ConcurrentModificationException}. |
37 |
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* However, iterators are designed to be used by only one thread at a time. |
38 |
tim |
1.1 |
* |
39 |
dl |
1.19 |
* <p> The allowed concurrency among update operations is guided by |
40 |
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* the optional <tt>concurrencyLevel</tt> constructor argument |
41 |
dl |
1.57 |
* (default <tt>16</tt>), which is used as a hint for internal sizing. The |
42 |
dl |
1.21 |
* table is internally partitioned to try to permit the indicated |
43 |
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* number of concurrent updates without contention. Because placement |
44 |
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* in hash tables is essentially random, the actual concurrency will |
45 |
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* vary. Ideally, you should choose a value to accommodate as many |
46 |
dl |
1.25 |
* threads as will ever concurrently modify the table. Using a |
47 |
dl |
1.21 |
* significantly higher value than you need can waste space and time, |
48 |
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* and a significantly lower value can lead to thread contention. But |
49 |
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* overestimates and underestimates within an order of magnitude do |
50 |
dl |
1.25 |
* not usually have much noticeable impact. A value of one is |
51 |
dl |
1.45 |
* appropriate when it is known that only one thread will modify and |
52 |
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* all others will only read. Also, resizing this or any other kind of |
53 |
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* hash table is a relatively slow operation, so, when possible, it is |
54 |
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* a good idea to provide estimates of expected table sizes in |
55 |
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* constructors. |
56 |
tim |
1.1 |
* |
57 |
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1.45 |
* <p>This class and its views and iterators implement all of the |
58 |
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* <em>optional</em> methods of the {@link Map} and {@link Iterator} |
59 |
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* interfaces. |
60 |
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1.23 |
* |
61 |
jsr166 |
1.68 |
* <p> Like {@link Hashtable} but unlike {@link HashMap}, this class |
62 |
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* does <em>not</em> allow <tt>null</tt> to be used as a key or value. |
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1.1 |
* |
64 |
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1.42 |
* <p>This class is a member of the |
65 |
jsr166 |
1.88 |
* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
66 |
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1.42 |
* Java Collections Framework</a>. |
67 |
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* |
68 |
dl |
1.8 |
* @since 1.5 |
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* @author Doug Lea |
70 |
dl |
1.27 |
* @param <K> the type of keys maintained by this map |
71 |
jsr166 |
1.64 |
* @param <V> the type of mapped values |
72 |
dl |
1.8 |
*/ |
73 |
tim |
1.1 |
public class ConcurrentHashMap<K, V> extends AbstractMap<K, V> |
74 |
dl |
1.48 |
implements ConcurrentMap<K, V>, Serializable { |
75 |
dl |
1.20 |
private static final long serialVersionUID = 7249069246763182397L; |
76 |
tim |
1.1 |
|
77 |
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/* |
78 |
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1.4 |
* The basic strategy is to subdivide the table among Segments, |
79 |
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* each of which itself is a concurrently readable hash table. |
80 |
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*/ |
81 |
tim |
1.1 |
|
82 |
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1.4 |
/* ---------------- Constants -------------- */ |
83 |
tim |
1.11 |
|
84 |
dl |
1.4 |
/** |
85 |
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1.56 |
* The default initial capacity for this table, |
86 |
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* used when not otherwise specified in a constructor. |
87 |
dl |
1.4 |
*/ |
88 |
dl |
1.57 |
static final int DEFAULT_INITIAL_CAPACITY = 16; |
89 |
dl |
1.56 |
|
90 |
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/** |
91 |
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* The default load factor for this table, used when not |
92 |
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* otherwise specified in a constructor. |
93 |
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*/ |
94 |
dl |
1.57 |
static final float DEFAULT_LOAD_FACTOR = 0.75f; |
95 |
dl |
1.56 |
|
96 |
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/** |
97 |
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* The default concurrency level for this table, used when not |
98 |
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* otherwise specified in a constructor. |
99 |
jsr166 |
1.59 |
*/ |
100 |
dl |
1.57 |
static final int DEFAULT_CONCURRENCY_LEVEL = 16; |
101 |
tim |
1.1 |
|
102 |
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/** |
103 |
dl |
1.4 |
* The maximum capacity, used if a higher value is implicitly |
104 |
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* specified by either of the constructors with arguments. MUST |
105 |
jsr166 |
1.68 |
* be a power of two <= 1<<30 to ensure that entries are indexable |
106 |
dl |
1.21 |
* using ints. |
107 |
dl |
1.4 |
*/ |
108 |
jsr166 |
1.64 |
static final int MAXIMUM_CAPACITY = 1 << 30; |
109 |
tim |
1.11 |
|
110 |
tim |
1.1 |
/** |
111 |
dl |
1.37 |
* The maximum number of segments to allow; used to bound |
112 |
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* constructor arguments. |
113 |
dl |
1.21 |
*/ |
114 |
dl |
1.41 |
static final int MAX_SEGMENTS = 1 << 16; // slightly conservative |
115 |
dl |
1.21 |
|
116 |
dl |
1.46 |
/** |
117 |
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* Number of unsynchronized retries in size and containsValue |
118 |
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* methods before resorting to locking. This is used to avoid |
119 |
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* unbounded retries if tables undergo continuous modification |
120 |
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* which would make it impossible to obtain an accurate result. |
121 |
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*/ |
122 |
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static final int RETRIES_BEFORE_LOCK = 2; |
123 |
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124 |
dl |
1.4 |
/* ---------------- Fields -------------- */ |
125 |
tim |
1.1 |
|
126 |
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/** |
127 |
dl |
1.9 |
* Mask value for indexing into segments. The upper bits of a |
128 |
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* key's hash code are used to choose the segment. |
129 |
jsr166 |
1.59 |
*/ |
130 |
dl |
1.41 |
final int segmentMask; |
131 |
tim |
1.1 |
|
132 |
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/** |
133 |
dl |
1.4 |
* Shift value for indexing within segments. |
134 |
jsr166 |
1.59 |
*/ |
135 |
dl |
1.41 |
final int segmentShift; |
136 |
tim |
1.1 |
|
137 |
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/** |
138 |
dl |
1.4 |
* The segments, each of which is a specialized hash table |
139 |
tim |
1.1 |
*/ |
140 |
dl |
1.71 |
final Segment<K,V>[] segments; |
141 |
dl |
1.4 |
|
142 |
dl |
1.41 |
transient Set<K> keySet; |
143 |
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transient Set<Map.Entry<K,V>> entrySet; |
144 |
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transient Collection<V> values; |
145 |
dl |
1.4 |
|
146 |
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/* ---------------- Small Utilities -------------- */ |
147 |
tim |
1.1 |
|
148 |
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/** |
149 |
dl |
1.89 |
* Applies a supplemental hash function to a given hashCode, which |
150 |
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* defends against poor quality hash functions. This is critical |
151 |
jsr166 |
1.90 |
* because ConcurrentHashMap uses power-of-two length hash tables, |
152 |
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* that otherwise encounter collisions for hashCodes that do not |
153 |
dl |
1.93 |
* differ in lower or upper bits. |
154 |
dl |
1.89 |
*/ |
155 |
jsr166 |
1.90 |
private static int hash(int h) { |
156 |
dl |
1.92 |
// Spread bits to regularize both segment and index locations, |
157 |
dl |
1.93 |
// using variant of single-word Wang/Jenkins hash. |
158 |
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h += (h << 15) ^ 0xffffcd7d; |
159 |
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h ^= (h >>> 10); |
160 |
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h += (h << 3); |
161 |
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h ^= (h >>> 6); |
162 |
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h += (h << 2) + (h << 14); |
163 |
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return h ^ (h >>> 16); |
164 |
dl |
1.4 |
} |
165 |
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166 |
tim |
1.1 |
/** |
167 |
dl |
1.44 |
* Returns the segment that should be used for key with given hash |
168 |
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* @param hash the hash code for the key |
169 |
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* @return the segment |
170 |
tim |
1.1 |
*/ |
171 |
dl |
1.41 |
final Segment<K,V> segmentFor(int hash) { |
172 |
dl |
1.71 |
return segments[(hash >>> segmentShift) & segmentMask]; |
173 |
dl |
1.4 |
} |
174 |
tim |
1.1 |
|
175 |
dl |
1.4 |
/* ---------------- Inner Classes -------------- */ |
176 |
tim |
1.1 |
|
177 |
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/** |
178 |
dl |
1.46 |
* ConcurrentHashMap list entry. Note that this is never exported |
179 |
jsr166 |
1.64 |
* out as a user-visible Map.Entry. |
180 |
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* |
181 |
dl |
1.46 |
* Because the value field is volatile, not final, it is legal wrt |
182 |
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* the Java Memory Model for an unsynchronized reader to see null |
183 |
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* instead of initial value when read via a data race. Although a |
184 |
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* reordering leading to this is not likely to ever actually |
185 |
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* occur, the Segment.readValueUnderLock method is used as a |
186 |
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* backup in case a null (pre-initialized) value is ever seen in |
187 |
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* an unsynchronized access method. |
188 |
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*/ |
189 |
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static final class HashEntry<K,V> { |
190 |
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final K key; |
191 |
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final int hash; |
192 |
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volatile V value; |
193 |
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final HashEntry<K,V> next; |
194 |
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195 |
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HashEntry(K key, int hash, HashEntry<K,V> next, V value) { |
196 |
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this.key = key; |
197 |
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this.hash = hash; |
198 |
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this.next = next; |
199 |
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this.value = value; |
200 |
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} |
201 |
dl |
1.72 |
|
202 |
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@SuppressWarnings("unchecked") |
203 |
|
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static final <K,V> HashEntry<K,V>[] newArray(int i) { |
204 |
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return new HashEntry[i]; |
205 |
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} |
206 |
dl |
1.46 |
} |
207 |
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208 |
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/** |
209 |
dl |
1.6 |
* Segments are specialized versions of hash tables. This |
210 |
dl |
1.4 |
* subclasses from ReentrantLock opportunistically, just to |
211 |
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* simplify some locking and avoid separate construction. |
212 |
jsr166 |
1.59 |
*/ |
213 |
dl |
1.41 |
static final class Segment<K,V> extends ReentrantLock implements Serializable { |
214 |
dl |
1.4 |
/* |
215 |
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* Segments maintain a table of entry lists that are ALWAYS |
216 |
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* kept in a consistent state, so can be read without locking. |
217 |
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* Next fields of nodes are immutable (final). All list |
218 |
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* additions are performed at the front of each bin. This |
219 |
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* makes it easy to check changes, and also fast to traverse. |
220 |
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* When nodes would otherwise be changed, new nodes are |
221 |
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* created to replace them. This works well for hash tables |
222 |
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* since the bin lists tend to be short. (The average length |
223 |
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* is less than two for the default load factor threshold.) |
224 |
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* |
225 |
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* Read operations can thus proceed without locking, but rely |
226 |
dl |
1.45 |
* on selected uses of volatiles to ensure that completed |
227 |
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* write operations performed by other threads are |
228 |
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* noticed. For most purposes, the "count" field, tracking the |
229 |
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* number of elements, serves as that volatile variable |
230 |
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* ensuring visibility. This is convenient because this field |
231 |
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* needs to be read in many read operations anyway: |
232 |
dl |
1.4 |
* |
233 |
dl |
1.45 |
* - All (unsynchronized) read operations must first read the |
234 |
dl |
1.4 |
* "count" field, and should not look at table entries if |
235 |
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* it is 0. |
236 |
tim |
1.11 |
* |
237 |
dl |
1.45 |
* - All (synchronized) write operations should write to |
238 |
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* the "count" field after structurally changing any bin. |
239 |
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* The operations must not take any action that could even |
240 |
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* momentarily cause a concurrent read operation to see |
241 |
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* inconsistent data. This is made easier by the nature of |
242 |
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* the read operations in Map. For example, no operation |
243 |
dl |
1.4 |
* can reveal that the table has grown but the threshold |
244 |
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* has not yet been updated, so there are no atomicity |
245 |
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* requirements for this with respect to reads. |
246 |
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* |
247 |
dl |
1.45 |
* As a guide, all critical volatile reads and writes to the |
248 |
|
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* count field are marked in code comments. |
249 |
dl |
1.4 |
*/ |
250 |
tim |
1.11 |
|
251 |
dl |
1.24 |
private static final long serialVersionUID = 2249069246763182397L; |
252 |
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|
253 |
dl |
1.4 |
/** |
254 |
|
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* The number of elements in this segment's region. |
255 |
jsr166 |
1.59 |
*/ |
256 |
dl |
1.4 |
transient volatile int count; |
257 |
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|
258 |
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/** |
259 |
dl |
1.45 |
* Number of updates that alter the size of the table. This is |
260 |
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* used during bulk-read methods to make sure they see a |
261 |
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* consistent snapshot: If modCounts change during a traversal |
262 |
dl |
1.46 |
* of segments computing size or checking containsValue, then |
263 |
dl |
1.45 |
* we might have an inconsistent view of state so (usually) |
264 |
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* must retry. |
265 |
dl |
1.21 |
*/ |
266 |
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transient int modCount; |
267 |
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|
268 |
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/** |
269 |
dl |
1.4 |
* The table is rehashed when its size exceeds this threshold. |
270 |
jsr166 |
1.68 |
* (The value of this field is always <tt>(int)(capacity * |
271 |
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* loadFactor)</tt>.) |
272 |
dl |
1.4 |
*/ |
273 |
dl |
1.41 |
transient int threshold; |
274 |
dl |
1.4 |
|
275 |
|
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/** |
276 |
jsr166 |
1.74 |
* The per-segment table. |
277 |
dl |
1.73 |
*/ |
278 |
dl |
1.71 |
transient volatile HashEntry<K,V>[] table; |
279 |
dl |
1.4 |
|
280 |
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/** |
281 |
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* The load factor for the hash table. Even though this value |
282 |
|
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* is same for all segments, it is replicated to avoid needing |
283 |
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* links to outer object. |
284 |
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* @serial |
285 |
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*/ |
286 |
dl |
1.41 |
final float loadFactor; |
287 |
tim |
1.1 |
|
288 |
dl |
1.4 |
Segment(int initialCapacity, float lf) { |
289 |
|
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loadFactor = lf; |
290 |
dl |
1.72 |
setTable(HashEntry.<K,V>newArray(initialCapacity)); |
291 |
|
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} |
292 |
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|
293 |
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@SuppressWarnings("unchecked") |
294 |
|
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static final <K,V> Segment<K,V>[] newArray(int i) { |
295 |
|
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return new Segment[i]; |
296 |
dl |
1.4 |
} |
297 |
tim |
1.1 |
|
298 |
dl |
1.4 |
/** |
299 |
jsr166 |
1.60 |
* Sets table to new HashEntry array. |
300 |
dl |
1.4 |
* Call only while holding lock or in constructor. |
301 |
jsr166 |
1.59 |
*/ |
302 |
dl |
1.71 |
void setTable(HashEntry<K,V>[] newTable) { |
303 |
dl |
1.45 |
threshold = (int)(newTable.length * loadFactor); |
304 |
dl |
1.4 |
table = newTable; |
305 |
dl |
1.45 |
} |
306 |
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|
307 |
|
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/** |
308 |
jsr166 |
1.60 |
* Returns properly casted first entry of bin for given hash. |
309 |
dl |
1.45 |
*/ |
310 |
|
|
HashEntry<K,V> getFirst(int hash) { |
311 |
dl |
1.71 |
HashEntry<K,V>[] tab = table; |
312 |
|
|
return tab[hash & (tab.length - 1)]; |
313 |
dl |
1.45 |
} |
314 |
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|
315 |
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/** |
316 |
jsr166 |
1.62 |
* Reads value field of an entry under lock. Called if value |
317 |
dl |
1.45 |
* field ever appears to be null. This is possible only if a |
318 |
|
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* compiler happens to reorder a HashEntry initialization with |
319 |
|
|
* its table assignment, which is legal under memory model |
320 |
|
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* but is not known to ever occur. |
321 |
|
|
*/ |
322 |
|
|
V readValueUnderLock(HashEntry<K,V> e) { |
323 |
|
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lock(); |
324 |
|
|
try { |
325 |
|
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return e.value; |
326 |
|
|
} finally { |
327 |
|
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unlock(); |
328 |
|
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} |
329 |
tim |
1.11 |
} |
330 |
dl |
1.4 |
|
331 |
|
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/* Specialized implementations of map methods */ |
332 |
tim |
1.11 |
|
333 |
dl |
1.29 |
V get(Object key, int hash) { |
334 |
dl |
1.4 |
if (count != 0) { // read-volatile |
335 |
dl |
1.45 |
HashEntry<K,V> e = getFirst(hash); |
336 |
dl |
1.4 |
while (e != null) { |
337 |
dl |
1.45 |
if (e.hash == hash && key.equals(e.key)) { |
338 |
|
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V v = e.value; |
339 |
|
|
if (v != null) |
340 |
|
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return v; |
341 |
|
|
return readValueUnderLock(e); // recheck |
342 |
|
|
} |
343 |
dl |
1.4 |
e = e.next; |
344 |
|
|
} |
345 |
|
|
} |
346 |
|
|
return null; |
347 |
|
|
} |
348 |
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|
349 |
|
|
boolean containsKey(Object key, int hash) { |
350 |
|
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if (count != 0) { // read-volatile |
351 |
dl |
1.45 |
HashEntry<K,V> e = getFirst(hash); |
352 |
dl |
1.4 |
while (e != null) { |
353 |
tim |
1.11 |
if (e.hash == hash && key.equals(e.key)) |
354 |
dl |
1.4 |
return true; |
355 |
|
|
e = e.next; |
356 |
|
|
} |
357 |
|
|
} |
358 |
|
|
return false; |
359 |
|
|
} |
360 |
tim |
1.11 |
|
361 |
dl |
1.4 |
boolean containsValue(Object value) { |
362 |
|
|
if (count != 0) { // read-volatile |
363 |
dl |
1.71 |
HashEntry<K,V>[] tab = table; |
364 |
dl |
1.4 |
int len = tab.length; |
365 |
dl |
1.45 |
for (int i = 0 ; i < len; i++) { |
366 |
dl |
1.72 |
for (HashEntry<K,V> e = tab[i]; e != null; e = e.next) { |
367 |
dl |
1.45 |
V v = e.value; |
368 |
|
|
if (v == null) // recheck |
369 |
|
|
v = readValueUnderLock(e); |
370 |
|
|
if (value.equals(v)) |
371 |
dl |
1.4 |
return true; |
372 |
dl |
1.45 |
} |
373 |
|
|
} |
374 |
dl |
1.4 |
} |
375 |
|
|
return false; |
376 |
|
|
} |
377 |
|
|
|
378 |
dl |
1.31 |
boolean replace(K key, int hash, V oldValue, V newValue) { |
379 |
|
|
lock(); |
380 |
|
|
try { |
381 |
dl |
1.45 |
HashEntry<K,V> e = getFirst(hash); |
382 |
|
|
while (e != null && (e.hash != hash || !key.equals(e.key))) |
383 |
dl |
1.31 |
e = e.next; |
384 |
dl |
1.45 |
|
385 |
|
|
boolean replaced = false; |
386 |
|
|
if (e != null && oldValue.equals(e.value)) { |
387 |
|
|
replaced = true; |
388 |
|
|
e.value = newValue; |
389 |
dl |
1.31 |
} |
390 |
dl |
1.45 |
return replaced; |
391 |
dl |
1.33 |
} finally { |
392 |
|
|
unlock(); |
393 |
|
|
} |
394 |
|
|
} |
395 |
|
|
|
396 |
|
|
V replace(K key, int hash, V newValue) { |
397 |
|
|
lock(); |
398 |
|
|
try { |
399 |
dl |
1.45 |
HashEntry<K,V> e = getFirst(hash); |
400 |
|
|
while (e != null && (e.hash != hash || !key.equals(e.key))) |
401 |
dl |
1.33 |
e = e.next; |
402 |
dl |
1.45 |
|
403 |
|
|
V oldValue = null; |
404 |
|
|
if (e != null) { |
405 |
|
|
oldValue = e.value; |
406 |
|
|
e.value = newValue; |
407 |
dl |
1.32 |
} |
408 |
dl |
1.45 |
return oldValue; |
409 |
dl |
1.31 |
} finally { |
410 |
|
|
unlock(); |
411 |
|
|
} |
412 |
|
|
} |
413 |
|
|
|
414 |
dl |
1.32 |
|
415 |
tim |
1.11 |
V put(K key, int hash, V value, boolean onlyIfAbsent) { |
416 |
dl |
1.4 |
lock(); |
417 |
|
|
try { |
418 |
dl |
1.9 |
int c = count; |
419 |
dl |
1.45 |
if (c++ > threshold) // ensure capacity |
420 |
|
|
rehash(); |
421 |
dl |
1.71 |
HashEntry<K,V>[] tab = table; |
422 |
dl |
1.9 |
int index = hash & (tab.length - 1); |
423 |
dl |
1.71 |
HashEntry<K,V> first = tab[index]; |
424 |
dl |
1.45 |
HashEntry<K,V> e = first; |
425 |
|
|
while (e != null && (e.hash != hash || !key.equals(e.key))) |
426 |
|
|
e = e.next; |
427 |
tim |
1.11 |
|
428 |
dl |
1.45 |
V oldValue; |
429 |
|
|
if (e != null) { |
430 |
|
|
oldValue = e.value; |
431 |
|
|
if (!onlyIfAbsent) |
432 |
|
|
e.value = value; |
433 |
|
|
} |
434 |
|
|
else { |
435 |
|
|
oldValue = null; |
436 |
|
|
++modCount; |
437 |
|
|
tab[index] = new HashEntry<K,V>(key, hash, first, value); |
438 |
|
|
count = c; // write-volatile |
439 |
dl |
1.4 |
} |
440 |
dl |
1.45 |
return oldValue; |
441 |
tim |
1.16 |
} finally { |
442 |
dl |
1.4 |
unlock(); |
443 |
|
|
} |
444 |
|
|
} |
445 |
|
|
|
446 |
dl |
1.45 |
void rehash() { |
447 |
dl |
1.71 |
HashEntry<K,V>[] oldTable = table; |
448 |
dl |
1.4 |
int oldCapacity = oldTable.length; |
449 |
|
|
if (oldCapacity >= MAXIMUM_CAPACITY) |
450 |
dl |
1.45 |
return; |
451 |
dl |
1.4 |
|
452 |
|
|
/* |
453 |
|
|
* Reclassify nodes in each list to new Map. Because we are |
454 |
|
|
* using power-of-two expansion, the elements from each bin |
455 |
|
|
* must either stay at same index, or move with a power of two |
456 |
|
|
* offset. We eliminate unnecessary node creation by catching |
457 |
|
|
* cases where old nodes can be reused because their next |
458 |
|
|
* fields won't change. Statistically, at the default |
459 |
dl |
1.29 |
* threshold, only about one-sixth of them need cloning when |
460 |
dl |
1.4 |
* a table doubles. The nodes they replace will be garbage |
461 |
|
|
* collectable as soon as they are no longer referenced by any |
462 |
|
|
* reader thread that may be in the midst of traversing table |
463 |
|
|
* right now. |
464 |
|
|
*/ |
465 |
tim |
1.11 |
|
466 |
dl |
1.72 |
HashEntry<K,V>[] newTable = HashEntry.newArray(oldCapacity<<1); |
467 |
dl |
1.45 |
threshold = (int)(newTable.length * loadFactor); |
468 |
dl |
1.4 |
int sizeMask = newTable.length - 1; |
469 |
|
|
for (int i = 0; i < oldCapacity ; i++) { |
470 |
|
|
// We need to guarantee that any existing reads of old Map can |
471 |
tim |
1.11 |
// proceed. So we cannot yet null out each bin. |
472 |
dl |
1.71 |
HashEntry<K,V> e = oldTable[i]; |
473 |
tim |
1.11 |
|
474 |
dl |
1.4 |
if (e != null) { |
475 |
|
|
HashEntry<K,V> next = e.next; |
476 |
|
|
int idx = e.hash & sizeMask; |
477 |
tim |
1.11 |
|
478 |
dl |
1.4 |
// Single node on list |
479 |
tim |
1.11 |
if (next == null) |
480 |
dl |
1.4 |
newTable[idx] = e; |
481 |
tim |
1.11 |
|
482 |
|
|
else { |
483 |
dl |
1.4 |
// Reuse trailing consecutive sequence at same slot |
484 |
|
|
HashEntry<K,V> lastRun = e; |
485 |
|
|
int lastIdx = idx; |
486 |
tim |
1.11 |
for (HashEntry<K,V> last = next; |
487 |
|
|
last != null; |
488 |
dl |
1.4 |
last = last.next) { |
489 |
|
|
int k = last.hash & sizeMask; |
490 |
|
|
if (k != lastIdx) { |
491 |
|
|
lastIdx = k; |
492 |
|
|
lastRun = last; |
493 |
|
|
} |
494 |
|
|
} |
495 |
|
|
newTable[lastIdx] = lastRun; |
496 |
tim |
1.11 |
|
497 |
dl |
1.4 |
// Clone all remaining nodes |
498 |
|
|
for (HashEntry<K,V> p = e; p != lastRun; p = p.next) { |
499 |
|
|
int k = p.hash & sizeMask; |
500 |
dl |
1.71 |
HashEntry<K,V> n = newTable[k]; |
501 |
dl |
1.45 |
newTable[k] = new HashEntry<K,V>(p.key, p.hash, |
502 |
|
|
n, p.value); |
503 |
dl |
1.4 |
} |
504 |
|
|
} |
505 |
|
|
} |
506 |
|
|
} |
507 |
dl |
1.45 |
table = newTable; |
508 |
dl |
1.4 |
} |
509 |
dl |
1.6 |
|
510 |
|
|
/** |
511 |
|
|
* Remove; match on key only if value null, else match both. |
512 |
|
|
*/ |
513 |
dl |
1.4 |
V remove(Object key, int hash, Object value) { |
514 |
tim |
1.11 |
lock(); |
515 |
dl |
1.4 |
try { |
516 |
dl |
1.45 |
int c = count - 1; |
517 |
dl |
1.71 |
HashEntry<K,V>[] tab = table; |
518 |
dl |
1.9 |
int index = hash & (tab.length - 1); |
519 |
dl |
1.71 |
HashEntry<K,V> first = tab[index]; |
520 |
dl |
1.4 |
HashEntry<K,V> e = first; |
521 |
dl |
1.45 |
while (e != null && (e.hash != hash || !key.equals(e.key))) |
522 |
dl |
1.4 |
e = e.next; |
523 |
dl |
1.45 |
|
524 |
|
|
V oldValue = null; |
525 |
|
|
if (e != null) { |
526 |
|
|
V v = e.value; |
527 |
|
|
if (value == null || value.equals(v)) { |
528 |
|
|
oldValue = v; |
529 |
|
|
// All entries following removed node can stay |
530 |
|
|
// in list, but all preceding ones need to be |
531 |
|
|
// cloned. |
532 |
|
|
++modCount; |
533 |
|
|
HashEntry<K,V> newFirst = e.next; |
534 |
|
|
for (HashEntry<K,V> p = first; p != e; p = p.next) |
535 |
jsr166 |
1.64 |
newFirst = new HashEntry<K,V>(p.key, p.hash, |
536 |
dl |
1.45 |
newFirst, p.value); |
537 |
|
|
tab[index] = newFirst; |
538 |
|
|
count = c; // write-volatile |
539 |
|
|
} |
540 |
dl |
1.4 |
} |
541 |
dl |
1.9 |
return oldValue; |
542 |
tim |
1.16 |
} finally { |
543 |
dl |
1.4 |
unlock(); |
544 |
|
|
} |
545 |
|
|
} |
546 |
|
|
|
547 |
|
|
void clear() { |
548 |
dl |
1.45 |
if (count != 0) { |
549 |
|
|
lock(); |
550 |
|
|
try { |
551 |
dl |
1.71 |
HashEntry<K,V>[] tab = table; |
552 |
dl |
1.45 |
for (int i = 0; i < tab.length ; i++) |
553 |
|
|
tab[i] = null; |
554 |
|
|
++modCount; |
555 |
|
|
count = 0; // write-volatile |
556 |
|
|
} finally { |
557 |
|
|
unlock(); |
558 |
|
|
} |
559 |
dl |
1.4 |
} |
560 |
|
|
} |
561 |
tim |
1.1 |
} |
562 |
|
|
|
563 |
|
|
|
564 |
tim |
1.11 |
|
565 |
dl |
1.4 |
/* ---------------- Public operations -------------- */ |
566 |
tim |
1.1 |
|
567 |
|
|
/** |
568 |
dl |
1.44 |
* Creates a new, empty map with the specified initial |
569 |
dl |
1.56 |
* capacity, load factor and concurrency level. |
570 |
tim |
1.1 |
* |
571 |
dl |
1.19 |
* @param initialCapacity the initial capacity. The implementation |
572 |
|
|
* performs internal sizing to accommodate this many elements. |
573 |
tim |
1.1 |
* @param loadFactor the load factor threshold, used to control resizing. |
574 |
dl |
1.56 |
* Resizing may be performed when the average number of elements per |
575 |
|
|
* bin exceeds this threshold. |
576 |
dl |
1.19 |
* @param concurrencyLevel the estimated number of concurrently |
577 |
|
|
* updating threads. The implementation performs internal sizing |
578 |
jsr166 |
1.64 |
* to try to accommodate this many threads. |
579 |
dl |
1.4 |
* @throws IllegalArgumentException if the initial capacity is |
580 |
dl |
1.19 |
* negative or the load factor or concurrencyLevel are |
581 |
dl |
1.4 |
* nonpositive. |
582 |
|
|
*/ |
583 |
tim |
1.11 |
public ConcurrentHashMap(int initialCapacity, |
584 |
dl |
1.19 |
float loadFactor, int concurrencyLevel) { |
585 |
|
|
if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0) |
586 |
dl |
1.4 |
throw new IllegalArgumentException(); |
587 |
|
|
|
588 |
dl |
1.21 |
if (concurrencyLevel > MAX_SEGMENTS) |
589 |
|
|
concurrencyLevel = MAX_SEGMENTS; |
590 |
|
|
|
591 |
dl |
1.4 |
// Find power-of-two sizes best matching arguments |
592 |
|
|
int sshift = 0; |
593 |
|
|
int ssize = 1; |
594 |
dl |
1.19 |
while (ssize < concurrencyLevel) { |
595 |
dl |
1.4 |
++sshift; |
596 |
|
|
ssize <<= 1; |
597 |
|
|
} |
598 |
dl |
1.9 |
segmentShift = 32 - sshift; |
599 |
dl |
1.8 |
segmentMask = ssize - 1; |
600 |
dl |
1.72 |
this.segments = Segment.newArray(ssize); |
601 |
dl |
1.4 |
|
602 |
|
|
if (initialCapacity > MAXIMUM_CAPACITY) |
603 |
|
|
initialCapacity = MAXIMUM_CAPACITY; |
604 |
|
|
int c = initialCapacity / ssize; |
605 |
tim |
1.11 |
if (c * ssize < initialCapacity) |
606 |
dl |
1.4 |
++c; |
607 |
|
|
int cap = 1; |
608 |
|
|
while (cap < c) |
609 |
|
|
cap <<= 1; |
610 |
|
|
|
611 |
|
|
for (int i = 0; i < this.segments.length; ++i) |
612 |
|
|
this.segments[i] = new Segment<K,V>(cap, loadFactor); |
613 |
tim |
1.1 |
} |
614 |
|
|
|
615 |
|
|
/** |
616 |
dl |
1.55 |
* Creates a new, empty map with the specified initial capacity |
617 |
jsr166 |
1.76 |
* and load factor and with the default concurrencyLevel (16). |
618 |
dl |
1.55 |
* |
619 |
|
|
* @param initialCapacity The implementation performs internal |
620 |
|
|
* sizing to accommodate this many elements. |
621 |
|
|
* @param loadFactor the load factor threshold, used to control resizing. |
622 |
jsr166 |
1.68 |
* Resizing may be performed when the average number of elements per |
623 |
|
|
* bin exceeds this threshold. |
624 |
dl |
1.55 |
* @throws IllegalArgumentException if the initial capacity of |
625 |
|
|
* elements is negative or the load factor is nonpositive |
626 |
jsr166 |
1.78 |
* |
627 |
|
|
* @since 1.6 |
628 |
dl |
1.55 |
*/ |
629 |
|
|
public ConcurrentHashMap(int initialCapacity, float loadFactor) { |
630 |
dl |
1.56 |
this(initialCapacity, loadFactor, DEFAULT_CONCURRENCY_LEVEL); |
631 |
dl |
1.55 |
} |
632 |
|
|
|
633 |
|
|
/** |
634 |
dl |
1.56 |
* Creates a new, empty map with the specified initial capacity, |
635 |
jsr166 |
1.76 |
* and with default load factor (0.75) and concurrencyLevel (16). |
636 |
tim |
1.1 |
* |
637 |
dl |
1.58 |
* @param initialCapacity the initial capacity. The implementation |
638 |
|
|
* performs internal sizing to accommodate this many elements. |
639 |
dl |
1.4 |
* @throws IllegalArgumentException if the initial capacity of |
640 |
|
|
* elements is negative. |
641 |
tim |
1.1 |
*/ |
642 |
|
|
public ConcurrentHashMap(int initialCapacity) { |
643 |
dl |
1.56 |
this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
644 |
tim |
1.1 |
} |
645 |
|
|
|
646 |
|
|
/** |
647 |
jsr166 |
1.76 |
* Creates a new, empty map with a default initial capacity (16), |
648 |
|
|
* load factor (0.75) and concurrencyLevel (16). |
649 |
tim |
1.1 |
*/ |
650 |
|
|
public ConcurrentHashMap() { |
651 |
dl |
1.56 |
this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
652 |
tim |
1.1 |
} |
653 |
|
|
|
654 |
|
|
/** |
655 |
jsr166 |
1.76 |
* Creates a new map with the same mappings as the given map. |
656 |
|
|
* The map is created with a capacity of 1.5 times the number |
657 |
|
|
* of mappings in the given map or 16 (whichever is greater), |
658 |
|
|
* and a default load factor (0.75) and concurrencyLevel (16). |
659 |
|
|
* |
660 |
jsr166 |
1.68 |
* @param m the map |
661 |
tim |
1.1 |
*/ |
662 |
jsr166 |
1.68 |
public ConcurrentHashMap(Map<? extends K, ? extends V> m) { |
663 |
|
|
this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1, |
664 |
dl |
1.56 |
DEFAULT_INITIAL_CAPACITY), |
665 |
|
|
DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL); |
666 |
jsr166 |
1.68 |
putAll(m); |
667 |
tim |
1.1 |
} |
668 |
|
|
|
669 |
dl |
1.56 |
/** |
670 |
|
|
* Returns <tt>true</tt> if this map contains no key-value mappings. |
671 |
|
|
* |
672 |
jsr166 |
1.68 |
* @return <tt>true</tt> if this map contains no key-value mappings |
673 |
dl |
1.56 |
*/ |
674 |
tim |
1.1 |
public boolean isEmpty() { |
675 |
dl |
1.71 |
final Segment<K,V>[] segments = this.segments; |
676 |
dl |
1.21 |
/* |
677 |
dl |
1.45 |
* We keep track of per-segment modCounts to avoid ABA |
678 |
dl |
1.21 |
* problems in which an element in one segment was added and |
679 |
|
|
* in another removed during traversal, in which case the |
680 |
|
|
* table was never actually empty at any point. Note the |
681 |
|
|
* similar use of modCounts in the size() and containsValue() |
682 |
|
|
* methods, which are the only other methods also susceptible |
683 |
|
|
* to ABA problems. |
684 |
|
|
*/ |
685 |
|
|
int[] mc = new int[segments.length]; |
686 |
|
|
int mcsum = 0; |
687 |
|
|
for (int i = 0; i < segments.length; ++i) { |
688 |
dl |
1.4 |
if (segments[i].count != 0) |
689 |
tim |
1.1 |
return false; |
690 |
jsr166 |
1.64 |
else |
691 |
dl |
1.21 |
mcsum += mc[i] = segments[i].modCount; |
692 |
|
|
} |
693 |
|
|
// If mcsum happens to be zero, then we know we got a snapshot |
694 |
|
|
// before any modifications at all were made. This is |
695 |
|
|
// probably common enough to bother tracking. |
696 |
|
|
if (mcsum != 0) { |
697 |
|
|
for (int i = 0; i < segments.length; ++i) { |
698 |
|
|
if (segments[i].count != 0 || |
699 |
jsr166 |
1.64 |
mc[i] != segments[i].modCount) |
700 |
dl |
1.21 |
return false; |
701 |
|
|
} |
702 |
|
|
} |
703 |
tim |
1.1 |
return true; |
704 |
|
|
} |
705 |
|
|
|
706 |
dl |
1.56 |
/** |
707 |
|
|
* Returns the number of key-value mappings in this map. If the |
708 |
|
|
* map contains more than <tt>Integer.MAX_VALUE</tt> elements, returns |
709 |
|
|
* <tt>Integer.MAX_VALUE</tt>. |
710 |
|
|
* |
711 |
jsr166 |
1.68 |
* @return the number of key-value mappings in this map |
712 |
dl |
1.56 |
*/ |
713 |
dl |
1.21 |
public int size() { |
714 |
dl |
1.71 |
final Segment<K,V>[] segments = this.segments; |
715 |
dl |
1.45 |
long sum = 0; |
716 |
|
|
long check = 0; |
717 |
dl |
1.21 |
int[] mc = new int[segments.length]; |
718 |
dl |
1.46 |
// Try a few times to get accurate count. On failure due to |
719 |
dl |
1.45 |
// continuous async changes in table, resort to locking. |
720 |
dl |
1.46 |
for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) { |
721 |
dl |
1.45 |
check = 0; |
722 |
|
|
sum = 0; |
723 |
dl |
1.21 |
int mcsum = 0; |
724 |
|
|
for (int i = 0; i < segments.length; ++i) { |
725 |
|
|
sum += segments[i].count; |
726 |
|
|
mcsum += mc[i] = segments[i].modCount; |
727 |
|
|
} |
728 |
|
|
if (mcsum != 0) { |
729 |
|
|
for (int i = 0; i < segments.length; ++i) { |
730 |
|
|
check += segments[i].count; |
731 |
|
|
if (mc[i] != segments[i].modCount) { |
732 |
|
|
check = -1; // force retry |
733 |
|
|
break; |
734 |
|
|
} |
735 |
|
|
} |
736 |
|
|
} |
737 |
jsr166 |
1.64 |
if (check == sum) |
738 |
dl |
1.45 |
break; |
739 |
|
|
} |
740 |
|
|
if (check != sum) { // Resort to locking all segments |
741 |
|
|
sum = 0; |
742 |
jsr166 |
1.64 |
for (int i = 0; i < segments.length; ++i) |
743 |
dl |
1.45 |
segments[i].lock(); |
744 |
jsr166 |
1.64 |
for (int i = 0; i < segments.length; ++i) |
745 |
dl |
1.45 |
sum += segments[i].count; |
746 |
jsr166 |
1.64 |
for (int i = 0; i < segments.length; ++i) |
747 |
dl |
1.45 |
segments[i].unlock(); |
748 |
dl |
1.21 |
} |
749 |
dl |
1.45 |
if (sum > Integer.MAX_VALUE) |
750 |
|
|
return Integer.MAX_VALUE; |
751 |
|
|
else |
752 |
|
|
return (int)sum; |
753 |
dl |
1.21 |
} |
754 |
|
|
|
755 |
tim |
1.1 |
/** |
756 |
jsr166 |
1.85 |
* Returns the value to which the specified key is mapped, |
757 |
|
|
* or {@code null} if this map contains no mapping for the key. |
758 |
|
|
* |
759 |
|
|
* <p>More formally, if this map contains a mapping from a key |
760 |
|
|
* {@code k} to a value {@code v} such that {@code key.equals(k)}, |
761 |
|
|
* then this method returns {@code v}; otherwise it returns |
762 |
|
|
* {@code null}. (There can be at most one such mapping.) |
763 |
tim |
1.1 |
* |
764 |
jsr166 |
1.68 |
* @throws NullPointerException if the specified key is null |
765 |
tim |
1.1 |
*/ |
766 |
tim |
1.11 |
public V get(Object key) { |
767 |
dl |
1.89 |
int hash = hash(key.hashCode()); |
768 |
dl |
1.29 |
return segmentFor(hash).get(key, hash); |
769 |
tim |
1.1 |
} |
770 |
|
|
|
771 |
|
|
/** |
772 |
|
|
* Tests if the specified object is a key in this table. |
773 |
tim |
1.11 |
* |
774 |
jsr166 |
1.68 |
* @param key possible key |
775 |
|
|
* @return <tt>true</tt> if and only if the specified object |
776 |
|
|
* is a key in this table, as determined by the |
777 |
|
|
* <tt>equals</tt> method; <tt>false</tt> otherwise. |
778 |
|
|
* @throws NullPointerException if the specified key is null |
779 |
tim |
1.1 |
*/ |
780 |
|
|
public boolean containsKey(Object key) { |
781 |
jsr166 |
1.91 |
int hash = hash(key.hashCode()); |
782 |
dl |
1.9 |
return segmentFor(hash).containsKey(key, hash); |
783 |
tim |
1.1 |
} |
784 |
|
|
|
785 |
|
|
/** |
786 |
|
|
* Returns <tt>true</tt> if this map maps one or more keys to the |
787 |
|
|
* specified value. Note: This method requires a full internal |
788 |
|
|
* traversal of the hash table, and so is much slower than |
789 |
|
|
* method <tt>containsKey</tt>. |
790 |
|
|
* |
791 |
jsr166 |
1.68 |
* @param value value whose presence in this map is to be tested |
792 |
tim |
1.1 |
* @return <tt>true</tt> if this map maps one or more keys to the |
793 |
jsr166 |
1.68 |
* specified value |
794 |
|
|
* @throws NullPointerException if the specified value is null |
795 |
tim |
1.1 |
*/ |
796 |
|
|
public boolean containsValue(Object value) { |
797 |
tim |
1.11 |
if (value == null) |
798 |
dl |
1.4 |
throw new NullPointerException(); |
799 |
jsr166 |
1.64 |
|
800 |
dl |
1.45 |
// See explanation of modCount use above |
801 |
tim |
1.1 |
|
802 |
dl |
1.71 |
final Segment<K,V>[] segments = this.segments; |
803 |
dl |
1.21 |
int[] mc = new int[segments.length]; |
804 |
dl |
1.45 |
|
805 |
dl |
1.46 |
// Try a few times without locking |
806 |
|
|
for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) { |
807 |
dl |
1.21 |
int sum = 0; |
808 |
|
|
int mcsum = 0; |
809 |
|
|
for (int i = 0; i < segments.length; ++i) { |
810 |
|
|
int c = segments[i].count; |
811 |
|
|
mcsum += mc[i] = segments[i].modCount; |
812 |
|
|
if (segments[i].containsValue(value)) |
813 |
|
|
return true; |
814 |
|
|
} |
815 |
|
|
boolean cleanSweep = true; |
816 |
|
|
if (mcsum != 0) { |
817 |
|
|
for (int i = 0; i < segments.length; ++i) { |
818 |
|
|
int c = segments[i].count; |
819 |
|
|
if (mc[i] != segments[i].modCount) { |
820 |
|
|
cleanSweep = false; |
821 |
|
|
break; |
822 |
|
|
} |
823 |
|
|
} |
824 |
|
|
} |
825 |
|
|
if (cleanSweep) |
826 |
|
|
return false; |
827 |
tim |
1.1 |
} |
828 |
dl |
1.45 |
// Resort to locking all segments |
829 |
jsr166 |
1.64 |
for (int i = 0; i < segments.length; ++i) |
830 |
dl |
1.45 |
segments[i].lock(); |
831 |
|
|
boolean found = false; |
832 |
|
|
try { |
833 |
|
|
for (int i = 0; i < segments.length; ++i) { |
834 |
|
|
if (segments[i].containsValue(value)) { |
835 |
|
|
found = true; |
836 |
|
|
break; |
837 |
|
|
} |
838 |
|
|
} |
839 |
|
|
} finally { |
840 |
jsr166 |
1.64 |
for (int i = 0; i < segments.length; ++i) |
841 |
dl |
1.45 |
segments[i].unlock(); |
842 |
|
|
} |
843 |
|
|
return found; |
844 |
tim |
1.1 |
} |
845 |
dl |
1.19 |
|
846 |
tim |
1.1 |
/** |
847 |
dl |
1.18 |
* Legacy method testing if some key maps into the specified value |
848 |
dl |
1.23 |
* in this table. This method is identical in functionality to |
849 |
jsr166 |
1.68 |
* {@link #containsValue}, and exists solely to ensure |
850 |
dl |
1.19 |
* full compatibility with class {@link java.util.Hashtable}, |
851 |
dl |
1.18 |
* which supported this method prior to introduction of the |
852 |
dl |
1.23 |
* Java Collections framework. |
853 |
dl |
1.17 |
|
854 |
jsr166 |
1.68 |
* @param value a value to search for |
855 |
|
|
* @return <tt>true</tt> if and only if some key maps to the |
856 |
|
|
* <tt>value</tt> argument in this table as |
857 |
|
|
* determined by the <tt>equals</tt> method; |
858 |
|
|
* <tt>false</tt> otherwise |
859 |
|
|
* @throws NullPointerException if the specified value is null |
860 |
tim |
1.1 |
*/ |
861 |
dl |
1.4 |
public boolean contains(Object value) { |
862 |
tim |
1.1 |
return containsValue(value); |
863 |
|
|
} |
864 |
|
|
|
865 |
|
|
/** |
866 |
jsr166 |
1.75 |
* Maps the specified key to the specified value in this table. |
867 |
|
|
* Neither the key nor the value can be null. |
868 |
dl |
1.4 |
* |
869 |
dl |
1.44 |
* <p> The value can be retrieved by calling the <tt>get</tt> method |
870 |
tim |
1.11 |
* with a key that is equal to the original key. |
871 |
dl |
1.4 |
* |
872 |
jsr166 |
1.68 |
* @param key key with which the specified value is to be associated |
873 |
|
|
* @param value value to be associated with the specified key |
874 |
|
|
* @return the previous value associated with <tt>key</tt>, or |
875 |
|
|
* <tt>null</tt> if there was no mapping for <tt>key</tt> |
876 |
|
|
* @throws NullPointerException if the specified key or value is null |
877 |
dl |
1.4 |
*/ |
878 |
tim |
1.11 |
public V put(K key, V value) { |
879 |
|
|
if (value == null) |
880 |
dl |
1.4 |
throw new NullPointerException(); |
881 |
dl |
1.89 |
int hash = hash(key.hashCode()); |
882 |
dl |
1.9 |
return segmentFor(hash).put(key, hash, value, false); |
883 |
dl |
1.4 |
} |
884 |
|
|
|
885 |
|
|
/** |
886 |
jsr166 |
1.68 |
* {@inheritDoc} |
887 |
|
|
* |
888 |
|
|
* @return the previous value associated with the specified key, |
889 |
|
|
* or <tt>null</tt> if there was no mapping for the key |
890 |
|
|
* @throws NullPointerException if the specified key or value is null |
891 |
dl |
1.51 |
*/ |
892 |
tim |
1.11 |
public V putIfAbsent(K key, V value) { |
893 |
|
|
if (value == null) |
894 |
dl |
1.4 |
throw new NullPointerException(); |
895 |
dl |
1.89 |
int hash = hash(key.hashCode()); |
896 |
dl |
1.9 |
return segmentFor(hash).put(key, hash, value, true); |
897 |
dl |
1.4 |
} |
898 |
|
|
|
899 |
|
|
/** |
900 |
tim |
1.1 |
* Copies all of the mappings from the specified map to this one. |
901 |
|
|
* These mappings replace any mappings that this map had for any of the |
902 |
jsr166 |
1.68 |
* keys currently in the specified map. |
903 |
tim |
1.1 |
* |
904 |
jsr166 |
1.68 |
* @param m mappings to be stored in this map |
905 |
tim |
1.1 |
*/ |
906 |
jsr166 |
1.68 |
public void putAll(Map<? extends K, ? extends V> m) { |
907 |
jsr166 |
1.84 |
for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) |
908 |
dl |
1.4 |
put(e.getKey(), e.getValue()); |
909 |
|
|
} |
910 |
|
|
|
911 |
|
|
/** |
912 |
jsr166 |
1.68 |
* Removes the key (and its corresponding value) from this map. |
913 |
|
|
* This method does nothing if the key is not in the map. |
914 |
dl |
1.4 |
* |
915 |
jsr166 |
1.68 |
* @param key the key that needs to be removed |
916 |
|
|
* @return the previous value associated with <tt>key</tt>, or |
917 |
jsr166 |
1.84 |
* <tt>null</tt> if there was no mapping for <tt>key</tt> |
918 |
jsr166 |
1.68 |
* @throws NullPointerException if the specified key is null |
919 |
dl |
1.4 |
*/ |
920 |
|
|
public V remove(Object key) { |
921 |
dl |
1.89 |
int hash = hash(key.hashCode()); |
922 |
dl |
1.9 |
return segmentFor(hash).remove(key, hash, null); |
923 |
dl |
1.4 |
} |
924 |
tim |
1.1 |
|
925 |
dl |
1.4 |
/** |
926 |
jsr166 |
1.68 |
* {@inheritDoc} |
927 |
|
|
* |
928 |
jsr166 |
1.69 |
* @throws NullPointerException if the specified key is null |
929 |
dl |
1.4 |
*/ |
930 |
dl |
1.13 |
public boolean remove(Object key, Object value) { |
931 |
dl |
1.89 |
int hash = hash(key.hashCode()); |
932 |
jsr166 |
1.68 |
if (value == null) |
933 |
jsr166 |
1.69 |
return false; |
934 |
dl |
1.13 |
return segmentFor(hash).remove(key, hash, value) != null; |
935 |
tim |
1.1 |
} |
936 |
dl |
1.31 |
|
937 |
|
|
/** |
938 |
jsr166 |
1.68 |
* {@inheritDoc} |
939 |
|
|
* |
940 |
|
|
* @throws NullPointerException if any of the arguments are null |
941 |
dl |
1.31 |
*/ |
942 |
|
|
public boolean replace(K key, V oldValue, V newValue) { |
943 |
|
|
if (oldValue == null || newValue == null) |
944 |
|
|
throw new NullPointerException(); |
945 |
dl |
1.89 |
int hash = hash(key.hashCode()); |
946 |
dl |
1.31 |
return segmentFor(hash).replace(key, hash, oldValue, newValue); |
947 |
dl |
1.32 |
} |
948 |
|
|
|
949 |
|
|
/** |
950 |
jsr166 |
1.68 |
* {@inheritDoc} |
951 |
|
|
* |
952 |
|
|
* @return the previous value associated with the specified key, |
953 |
|
|
* or <tt>null</tt> if there was no mapping for the key |
954 |
|
|
* @throws NullPointerException if the specified key or value is null |
955 |
dl |
1.32 |
*/ |
956 |
dl |
1.33 |
public V replace(K key, V value) { |
957 |
dl |
1.32 |
if (value == null) |
958 |
|
|
throw new NullPointerException(); |
959 |
dl |
1.89 |
int hash = hash(key.hashCode()); |
960 |
dl |
1.33 |
return segmentFor(hash).replace(key, hash, value); |
961 |
dl |
1.31 |
} |
962 |
|
|
|
963 |
tim |
1.1 |
/** |
964 |
jsr166 |
1.68 |
* Removes all of the mappings from this map. |
965 |
tim |
1.1 |
*/ |
966 |
|
|
public void clear() { |
967 |
tim |
1.11 |
for (int i = 0; i < segments.length; ++i) |
968 |
dl |
1.4 |
segments[i].clear(); |
969 |
tim |
1.1 |
} |
970 |
|
|
|
971 |
|
|
/** |
972 |
jsr166 |
1.68 |
* Returns a {@link Set} view of the keys contained in this map. |
973 |
|
|
* The set is backed by the map, so changes to the map are |
974 |
|
|
* reflected in the set, and vice-versa. The set supports element |
975 |
|
|
* removal, which removes the corresponding mapping from this map, |
976 |
|
|
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, |
977 |
|
|
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> |
978 |
|
|
* operations. It does not support the <tt>add</tt> or |
979 |
tim |
1.1 |
* <tt>addAll</tt> operations. |
980 |
jsr166 |
1.68 |
* |
981 |
|
|
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator |
982 |
|
|
* that will never throw {@link ConcurrentModificationException}, |
983 |
dl |
1.14 |
* and guarantees to traverse elements as they existed upon |
984 |
|
|
* construction of the iterator, and may (but is not guaranteed to) |
985 |
|
|
* reflect any modifications subsequent to construction. |
986 |
tim |
1.1 |
*/ |
987 |
|
|
public Set<K> keySet() { |
988 |
|
|
Set<K> ks = keySet; |
989 |
dl |
1.8 |
return (ks != null) ? ks : (keySet = new KeySet()); |
990 |
tim |
1.1 |
} |
991 |
|
|
|
992 |
|
|
/** |
993 |
jsr166 |
1.68 |
* Returns a {@link Collection} view of the values contained in this map. |
994 |
|
|
* The collection is backed by the map, so changes to the map are |
995 |
|
|
* reflected in the collection, and vice-versa. The collection |
996 |
|
|
* supports element removal, which removes the corresponding |
997 |
|
|
* mapping from this map, via the <tt>Iterator.remove</tt>, |
998 |
|
|
* <tt>Collection.remove</tt>, <tt>removeAll</tt>, |
999 |
|
|
* <tt>retainAll</tt>, and <tt>clear</tt> operations. It does not |
1000 |
|
|
* support the <tt>add</tt> or <tt>addAll</tt> operations. |
1001 |
|
|
* |
1002 |
|
|
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator |
1003 |
|
|
* that will never throw {@link ConcurrentModificationException}, |
1004 |
dl |
1.14 |
* and guarantees to traverse elements as they existed upon |
1005 |
|
|
* construction of the iterator, and may (but is not guaranteed to) |
1006 |
|
|
* reflect any modifications subsequent to construction. |
1007 |
tim |
1.1 |
*/ |
1008 |
|
|
public Collection<V> values() { |
1009 |
|
|
Collection<V> vs = values; |
1010 |
dl |
1.8 |
return (vs != null) ? vs : (values = new Values()); |
1011 |
tim |
1.1 |
} |
1012 |
|
|
|
1013 |
|
|
/** |
1014 |
jsr166 |
1.68 |
* Returns a {@link Set} view of the mappings contained in this map. |
1015 |
|
|
* The set is backed by the map, so changes to the map are |
1016 |
|
|
* reflected in the set, and vice-versa. The set supports element |
1017 |
|
|
* removal, which removes the corresponding mapping from the map, |
1018 |
|
|
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, |
1019 |
|
|
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> |
1020 |
|
|
* operations. It does not support the <tt>add</tt> or |
1021 |
|
|
* <tt>addAll</tt> operations. |
1022 |
|
|
* |
1023 |
|
|
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator |
1024 |
|
|
* that will never throw {@link ConcurrentModificationException}, |
1025 |
dl |
1.14 |
* and guarantees to traverse elements as they existed upon |
1026 |
|
|
* construction of the iterator, and may (but is not guaranteed to) |
1027 |
|
|
* reflect any modifications subsequent to construction. |
1028 |
tim |
1.1 |
*/ |
1029 |
|
|
public Set<Map.Entry<K,V>> entrySet() { |
1030 |
|
|
Set<Map.Entry<K,V>> es = entrySet; |
1031 |
jsr166 |
1.65 |
return (es != null) ? es : (entrySet = new EntrySet()); |
1032 |
tim |
1.1 |
} |
1033 |
|
|
|
1034 |
|
|
/** |
1035 |
|
|
* Returns an enumeration of the keys in this table. |
1036 |
|
|
* |
1037 |
jsr166 |
1.70 |
* @return an enumeration of the keys in this table |
1038 |
|
|
* @see #keySet |
1039 |
tim |
1.1 |
*/ |
1040 |
dl |
1.4 |
public Enumeration<K> keys() { |
1041 |
tim |
1.1 |
return new KeyIterator(); |
1042 |
|
|
} |
1043 |
|
|
|
1044 |
|
|
/** |
1045 |
|
|
* Returns an enumeration of the values in this table. |
1046 |
|
|
* |
1047 |
jsr166 |
1.70 |
* @return an enumeration of the values in this table |
1048 |
|
|
* @see #values |
1049 |
tim |
1.1 |
*/ |
1050 |
dl |
1.4 |
public Enumeration<V> elements() { |
1051 |
tim |
1.1 |
return new ValueIterator(); |
1052 |
|
|
} |
1053 |
|
|
|
1054 |
dl |
1.4 |
/* ---------------- Iterator Support -------------- */ |
1055 |
tim |
1.11 |
|
1056 |
jsr166 |
1.82 |
abstract class HashIterator { |
1057 |
dl |
1.41 |
int nextSegmentIndex; |
1058 |
|
|
int nextTableIndex; |
1059 |
dl |
1.71 |
HashEntry<K,V>[] currentTable; |
1060 |
dl |
1.41 |
HashEntry<K, V> nextEntry; |
1061 |
dl |
1.30 |
HashEntry<K, V> lastReturned; |
1062 |
tim |
1.1 |
|
1063 |
dl |
1.41 |
HashIterator() { |
1064 |
dl |
1.8 |
nextSegmentIndex = segments.length - 1; |
1065 |
dl |
1.4 |
nextTableIndex = -1; |
1066 |
|
|
advance(); |
1067 |
tim |
1.1 |
} |
1068 |
|
|
|
1069 |
|
|
public boolean hasMoreElements() { return hasNext(); } |
1070 |
|
|
|
1071 |
dl |
1.41 |
final void advance() { |
1072 |
dl |
1.4 |
if (nextEntry != null && (nextEntry = nextEntry.next) != null) |
1073 |
|
|
return; |
1074 |
tim |
1.11 |
|
1075 |
dl |
1.4 |
while (nextTableIndex >= 0) { |
1076 |
dl |
1.71 |
if ( (nextEntry = currentTable[nextTableIndex--]) != null) |
1077 |
dl |
1.4 |
return; |
1078 |
|
|
} |
1079 |
tim |
1.11 |
|
1080 |
dl |
1.4 |
while (nextSegmentIndex >= 0) { |
1081 |
dl |
1.71 |
Segment<K,V> seg = segments[nextSegmentIndex--]; |
1082 |
dl |
1.4 |
if (seg.count != 0) { |
1083 |
|
|
currentTable = seg.table; |
1084 |
dl |
1.8 |
for (int j = currentTable.length - 1; j >= 0; --j) { |
1085 |
dl |
1.71 |
if ( (nextEntry = currentTable[j]) != null) { |
1086 |
dl |
1.8 |
nextTableIndex = j - 1; |
1087 |
dl |
1.4 |
return; |
1088 |
|
|
} |
1089 |
tim |
1.1 |
} |
1090 |
|
|
} |
1091 |
|
|
} |
1092 |
|
|
} |
1093 |
|
|
|
1094 |
dl |
1.4 |
public boolean hasNext() { return nextEntry != null; } |
1095 |
tim |
1.1 |
|
1096 |
dl |
1.4 |
HashEntry<K,V> nextEntry() { |
1097 |
|
|
if (nextEntry == null) |
1098 |
tim |
1.1 |
throw new NoSuchElementException(); |
1099 |
dl |
1.4 |
lastReturned = nextEntry; |
1100 |
|
|
advance(); |
1101 |
|
|
return lastReturned; |
1102 |
tim |
1.1 |
} |
1103 |
|
|
|
1104 |
|
|
public void remove() { |
1105 |
|
|
if (lastReturned == null) |
1106 |
|
|
throw new IllegalStateException(); |
1107 |
|
|
ConcurrentHashMap.this.remove(lastReturned.key); |
1108 |
|
|
lastReturned = null; |
1109 |
|
|
} |
1110 |
dl |
1.4 |
} |
1111 |
|
|
|
1112 |
jsr166 |
1.82 |
final class KeyIterator |
1113 |
|
|
extends HashIterator |
1114 |
|
|
implements Iterator<K>, Enumeration<K> |
1115 |
|
|
{ |
1116 |
|
|
public K next() { return super.nextEntry().key; } |
1117 |
dl |
1.4 |
public K nextElement() { return super.nextEntry().key; } |
1118 |
|
|
} |
1119 |
|
|
|
1120 |
jsr166 |
1.82 |
final class ValueIterator |
1121 |
|
|
extends HashIterator |
1122 |
|
|
implements Iterator<V>, Enumeration<V> |
1123 |
|
|
{ |
1124 |
|
|
public V next() { return super.nextEntry().value; } |
1125 |
dl |
1.4 |
public V nextElement() { return super.nextEntry().value; } |
1126 |
|
|
} |
1127 |
tim |
1.1 |
|
1128 |
dl |
1.30 |
/** |
1129 |
dl |
1.79 |
* Custom Entry class used by EntryIterator.next(), that relays |
1130 |
|
|
* setValue changes to the underlying map. |
1131 |
jsr166 |
1.80 |
*/ |
1132 |
jsr166 |
1.83 |
final class WriteThroughEntry |
1133 |
jsr166 |
1.81 |
extends AbstractMap.SimpleEntry<K,V> |
1134 |
|
|
{ |
1135 |
jsr166 |
1.83 |
WriteThroughEntry(K k, V v) { |
1136 |
jsr166 |
1.80 |
super(k,v); |
1137 |
dl |
1.79 |
} |
1138 |
|
|
|
1139 |
|
|
/** |
1140 |
|
|
* Set our entry's value and write through to the map. The |
1141 |
|
|
* value to return is somewhat arbitrary here. Since a |
1142 |
|
|
* WriteThroughEntry does not necessarily track asynchronous |
1143 |
|
|
* changes, the most recent "previous" value could be |
1144 |
jsr166 |
1.81 |
* different from what we return (or could even have been |
1145 |
dl |
1.79 |
* removed in which case the put will re-establish). We do not |
1146 |
|
|
* and cannot guarantee more. |
1147 |
|
|
*/ |
1148 |
|
|
public V setValue(V value) { |
1149 |
|
|
if (value == null) throw new NullPointerException(); |
1150 |
|
|
V v = super.setValue(value); |
1151 |
jsr166 |
1.83 |
ConcurrentHashMap.this.put(getKey(), value); |
1152 |
dl |
1.79 |
return v; |
1153 |
dl |
1.30 |
} |
1154 |
dl |
1.79 |
} |
1155 |
dl |
1.30 |
|
1156 |
jsr166 |
1.82 |
final class EntryIterator |
1157 |
|
|
extends HashIterator |
1158 |
|
|
implements Iterator<Entry<K,V>> |
1159 |
|
|
{ |
1160 |
dl |
1.79 |
public Map.Entry<K,V> next() { |
1161 |
|
|
HashEntry<K,V> e = super.nextEntry(); |
1162 |
jsr166 |
1.83 |
return new WriteThroughEntry(e.key, e.value); |
1163 |
dl |
1.30 |
} |
1164 |
tim |
1.1 |
} |
1165 |
|
|
|
1166 |
dl |
1.41 |
final class KeySet extends AbstractSet<K> { |
1167 |
dl |
1.4 |
public Iterator<K> iterator() { |
1168 |
|
|
return new KeyIterator(); |
1169 |
|
|
} |
1170 |
|
|
public int size() { |
1171 |
|
|
return ConcurrentHashMap.this.size(); |
1172 |
|
|
} |
1173 |
|
|
public boolean contains(Object o) { |
1174 |
|
|
return ConcurrentHashMap.this.containsKey(o); |
1175 |
|
|
} |
1176 |
|
|
public boolean remove(Object o) { |
1177 |
|
|
return ConcurrentHashMap.this.remove(o) != null; |
1178 |
|
|
} |
1179 |
|
|
public void clear() { |
1180 |
|
|
ConcurrentHashMap.this.clear(); |
1181 |
|
|
} |
1182 |
tim |
1.1 |
} |
1183 |
|
|
|
1184 |
dl |
1.41 |
final class Values extends AbstractCollection<V> { |
1185 |
dl |
1.4 |
public Iterator<V> iterator() { |
1186 |
|
|
return new ValueIterator(); |
1187 |
|
|
} |
1188 |
|
|
public int size() { |
1189 |
|
|
return ConcurrentHashMap.this.size(); |
1190 |
|
|
} |
1191 |
|
|
public boolean contains(Object o) { |
1192 |
|
|
return ConcurrentHashMap.this.containsValue(o); |
1193 |
|
|
} |
1194 |
|
|
public void clear() { |
1195 |
|
|
ConcurrentHashMap.this.clear(); |
1196 |
|
|
} |
1197 |
tim |
1.1 |
} |
1198 |
|
|
|
1199 |
dl |
1.41 |
final class EntrySet extends AbstractSet<Map.Entry<K,V>> { |
1200 |
dl |
1.4 |
public Iterator<Map.Entry<K,V>> iterator() { |
1201 |
|
|
return new EntryIterator(); |
1202 |
|
|
} |
1203 |
|
|
public boolean contains(Object o) { |
1204 |
|
|
if (!(o instanceof Map.Entry)) |
1205 |
|
|
return false; |
1206 |
dl |
1.71 |
Map.Entry<?,?> e = (Map.Entry<?,?>)o; |
1207 |
dl |
1.4 |
V v = ConcurrentHashMap.this.get(e.getKey()); |
1208 |
|
|
return v != null && v.equals(e.getValue()); |
1209 |
|
|
} |
1210 |
|
|
public boolean remove(Object o) { |
1211 |
|
|
if (!(o instanceof Map.Entry)) |
1212 |
|
|
return false; |
1213 |
dl |
1.71 |
Map.Entry<?,?> e = (Map.Entry<?,?>)o; |
1214 |
dl |
1.13 |
return ConcurrentHashMap.this.remove(e.getKey(), e.getValue()); |
1215 |
dl |
1.4 |
} |
1216 |
|
|
public int size() { |
1217 |
|
|
return ConcurrentHashMap.this.size(); |
1218 |
|
|
} |
1219 |
|
|
public void clear() { |
1220 |
|
|
ConcurrentHashMap.this.clear(); |
1221 |
dl |
1.30 |
} |
1222 |
|
|
} |
1223 |
|
|
|
1224 |
dl |
1.4 |
/* ---------------- Serialization Support -------------- */ |
1225 |
|
|
|
1226 |
tim |
1.1 |
/** |
1227 |
jsr166 |
1.68 |
* Save the state of the <tt>ConcurrentHashMap</tt> instance to a |
1228 |
|
|
* stream (i.e., serialize it). |
1229 |
dl |
1.8 |
* @param s the stream |
1230 |
tim |
1.1 |
* @serialData |
1231 |
|
|
* the key (Object) and value (Object) |
1232 |
|
|
* for each key-value mapping, followed by a null pair. |
1233 |
|
|
* The key-value mappings are emitted in no particular order. |
1234 |
|
|
*/ |
1235 |
|
|
private void writeObject(java.io.ObjectOutputStream s) throws IOException { |
1236 |
|
|
s.defaultWriteObject(); |
1237 |
|
|
|
1238 |
|
|
for (int k = 0; k < segments.length; ++k) { |
1239 |
dl |
1.71 |
Segment<K,V> seg = segments[k]; |
1240 |
dl |
1.2 |
seg.lock(); |
1241 |
|
|
try { |
1242 |
dl |
1.71 |
HashEntry<K,V>[] tab = seg.table; |
1243 |
dl |
1.4 |
for (int i = 0; i < tab.length; ++i) { |
1244 |
dl |
1.71 |
for (HashEntry<K,V> e = tab[i]; e != null; e = e.next) { |
1245 |
dl |
1.4 |
s.writeObject(e.key); |
1246 |
|
|
s.writeObject(e.value); |
1247 |
|
|
} |
1248 |
|
|
} |
1249 |
tim |
1.16 |
} finally { |
1250 |
dl |
1.2 |
seg.unlock(); |
1251 |
|
|
} |
1252 |
tim |
1.1 |
} |
1253 |
|
|
s.writeObject(null); |
1254 |
|
|
s.writeObject(null); |
1255 |
|
|
} |
1256 |
|
|
|
1257 |
|
|
/** |
1258 |
jsr166 |
1.68 |
* Reconstitute the <tt>ConcurrentHashMap</tt> instance from a |
1259 |
|
|
* stream (i.e., deserialize it). |
1260 |
dl |
1.8 |
* @param s the stream |
1261 |
tim |
1.1 |
*/ |
1262 |
|
|
private void readObject(java.io.ObjectInputStream s) |
1263 |
|
|
throws IOException, ClassNotFoundException { |
1264 |
|
|
s.defaultReadObject(); |
1265 |
|
|
|
1266 |
dl |
1.4 |
// Initialize each segment to be minimally sized, and let grow. |
1267 |
|
|
for (int i = 0; i < segments.length; ++i) { |
1268 |
dl |
1.73 |
segments[i].setTable(new HashEntry[1]); |
1269 |
dl |
1.4 |
} |
1270 |
tim |
1.1 |
|
1271 |
|
|
// Read the keys and values, and put the mappings in the table |
1272 |
dl |
1.9 |
for (;;) { |
1273 |
tim |
1.1 |
K key = (K) s.readObject(); |
1274 |
|
|
V value = (V) s.readObject(); |
1275 |
|
|
if (key == null) |
1276 |
|
|
break; |
1277 |
|
|
put(key, value); |
1278 |
|
|
} |
1279 |
|
|
} |
1280 |
|
|
} |