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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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*/ |
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|
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package java.util.concurrent; |
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import java.util.concurrent.locks.*; |
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import java.util.*; |
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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; |
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|
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/** |
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* A hash table supporting full concurrency of retrievals and |
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* adjustable expected concurrency for updates. This class obeys the |
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* same functional specification as {@link java.util.Hashtable}, and |
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* includes versions of methods corresponding to each method of |
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* <tt>Hashtable</tt>. However, even though all operations are |
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* thread-safe, retrieval operations do <em>not</em> entail locking, |
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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 |
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* thread safety but not on its synchronization details. |
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* |
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* <p> Retrieval operations (including <tt>get</tt>) generally do not |
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* block, so may overlap with update operations (including |
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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 |
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* upon their onset. For aggregate operations such as <tt>putAll</tt> |
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* and <tt>clear</tt>, concurrent retrievals may reflect insertion or |
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* removal of only some entries. Similarly, Iterators and |
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* Enumerations return elements reflecting the state of the hash table |
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* at some point at or since the creation of the iterator/enumeration. |
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* They do <em>not</em> throw |
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* {@link ConcurrentModificationException}. However, iterators are |
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* designed to be used by only one thread at a time. |
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* |
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* <p> The allowed concurrency among update operations is guided by |
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* the optional <tt>concurrencyLevel</tt> constructor argument |
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* (default 16), which is used as a hint for internal sizing. The |
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* table is internally partitioned to try to permit the indicated |
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* number of concurrent updates without contention. Because placement |
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* in hash tables is essentially random, the actual concurrency will |
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* vary. Ideally, you should choose a value to accommodate as many |
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* threads as will ever concurrently modify the table. Using a |
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* significantly higher value than you need can waste space and time, |
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* and a significantly lower value can lead to thread contention. But |
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* overestimates and underestimates within an order of magnitude do |
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* not usually have much noticeable impact. A value of one is |
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* appropriate when it is known that only one thread will modify and |
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* all others will only read. Also, resizing this or any other kind of |
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* hash table is a relatively slow operation, so, when possible, it is |
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* a good idea to provide estimates of expected table sizes in |
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* constructors. |
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* |
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* <p>This class and its views and iterators implement all of the |
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* <em>optional</em> methods of the {@link Map} and {@link Iterator} |
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* interfaces. |
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* |
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* <p> Like {@link java.util.Hashtable} but unlike {@link |
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* java.util.HashMap}, this class does NOT allow <tt>null</tt> to be |
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* used as a key or value. |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* Java Collections Framework</a>. |
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* |
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* @since 1.5 |
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* @author Doug Lea |
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* @param <K> the type of keys maintained by this map |
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* @param <V> the type of mapped values |
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*/ |
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public class ConcurrentHashMap<K, V> extends AbstractMap<K, V> |
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implements ConcurrentMap<K, V>, Cloneable, Serializable { |
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private static final long serialVersionUID = 7249069246763182397L; |
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|
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/* |
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* The basic strategy is to subdivide the table among Segments, |
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* each of which itself is a concurrently readable hash table. |
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*/ |
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|
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/* ---------------- Constants -------------- */ |
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|
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/** |
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* The default initial number of table slots for this table. |
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* Used when not otherwise specified in constructor. |
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*/ |
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static int DEFAULT_INITIAL_CAPACITY = 16; |
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|
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/** |
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* The maximum capacity, used if a higher value is implicitly |
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* specified by either of the constructors with arguments. MUST |
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* be a power of two <= 1<<30 to ensure that entries are indexible |
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* using ints. |
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*/ |
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static final int MAXIMUM_CAPACITY = 1 << 30; |
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|
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/** |
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* The default load factor for this table. Used when not |
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* otherwise specified in constructor. |
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*/ |
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static final float DEFAULT_LOAD_FACTOR = 0.75f; |
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|
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/** |
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* The default number of concurrency control segments. |
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**/ |
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static final int DEFAULT_SEGMENTS = 16; |
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|
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/** |
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* The maximum number of segments to allow; used to bound |
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* constructor arguments. |
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*/ |
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static final int MAX_SEGMENTS = 1 << 16; // slightly conservative |
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|
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/* ---------------- Fields -------------- */ |
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|
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/** |
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* Mask value for indexing into segments. The upper bits of a |
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* key's hash code are used to choose the segment. |
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**/ |
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final int segmentMask; |
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|
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/** |
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* Shift value for indexing within segments. |
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**/ |
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final int segmentShift; |
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|
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/** |
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* The segments, each of which is a specialized hash table |
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*/ |
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final Segment[] segments; |
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|
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transient Set<K> keySet; |
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transient Set<Map.Entry<K,V>> entrySet; |
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transient Collection<V> values; |
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|
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/* ---------------- Small Utilities -------------- */ |
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|
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/** |
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* Returns a hash code for non-null Object x. |
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* Uses the same hash code spreader as most other java.util hash tables. |
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* @param x the object serving as a key |
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* @return the hash code |
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*/ |
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static int hash(Object x) { |
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int h = x.hashCode(); |
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h += ~(h << 9); |
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h ^= (h >>> 14); |
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h += (h << 4); |
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h ^= (h >>> 10); |
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return h; |
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} |
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|
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/** |
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* Returns the segment that should be used for key with given hash |
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* @param hash the hash code for the key |
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* @return the segment |
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*/ |
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final Segment<K,V> segmentFor(int hash) { |
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return (Segment<K,V>) segments[(hash >>> segmentShift) & segmentMask]; |
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} |
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|
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/* ---------------- Inner Classes -------------- */ |
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|
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/** |
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* Segments are specialized versions of hash tables. This |
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* subclasses from ReentrantLock opportunistically, just to |
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* simplify some locking and avoid separate construction. |
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**/ |
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static final class Segment<K,V> extends ReentrantLock implements Serializable { |
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/* |
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* Segments maintain a table of entry lists that are ALWAYS |
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* kept in a consistent state, so can be read without locking. |
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* Next fields of nodes are immutable (final). All list |
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* additions are performed at the front of each bin. This |
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* makes it easy to check changes, and also fast to traverse. |
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* When nodes would otherwise be changed, new nodes are |
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* created to replace them. This works well for hash tables |
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* since the bin lists tend to be short. (The average length |
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* is less than two for the default load factor threshold.) |
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* |
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* Read operations can thus proceed without locking, but rely |
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* on selected uses of volatiles to ensure that completed |
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* write operations performed by other threads are |
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* noticed. For most purposes, the "count" field, tracking the |
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* number of elements, serves as that volatile variable |
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* ensuring visibility. This is convenient because this field |
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* needs to be read in many read operations anyway: |
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* |
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* - All (unsynchronized) read operations must first read the |
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* "count" field, and should not look at table entries if |
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* it is 0. |
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* |
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* - All (synchronized) write operations should write to |
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* the "count" field after structurally changing any bin. |
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* The operations must not take any action that could even |
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* momentarily cause a concurrent read operation to see |
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* inconsistent data. This is made easier by the nature of |
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* the read operations in Map. For example, no operation |
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* can reveal that the table has grown but the threshold |
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* has not yet been updated, so there are no atomicity |
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* requirements for this with respect to reads. |
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* |
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* As a guide, all critical volatile reads and writes to the |
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* count field are marked in code comments. |
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*/ |
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|
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private static final long serialVersionUID = 2249069246763182397L; |
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|
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/** |
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* The number of elements in this segment's region. |
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**/ |
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transient volatile int count; |
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|
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/** |
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* Number of updates that alter the size of the table. This is |
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* used during bulk-read methods to make sure they see a |
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* consistent snapshot: If modCounts change during a traversal |
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* of segments computing size or checking contatinsValue, then |
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* we might have an inconsistent view of state so (usually) |
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* must retry. |
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*/ |
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transient int modCount; |
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|
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/** |
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* The table is rehashed when its size exceeds this threshold. |
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* (The value of this field is always (int)(capacity * |
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* loadFactor).) |
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*/ |
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transient int threshold; |
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|
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/** |
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* The per-segment table. Declared as a raw type, casted |
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* to HashEntry<K,V> on each use. |
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*/ |
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transient volatile HashEntry[] table; |
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|
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/** |
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* The load factor for the hash table. Even though this value |
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* is same for all segments, it is replicated to avoid needing |
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* links to outer object. |
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* @serial |
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*/ |
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final float loadFactor; |
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|
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Segment(int initialCapacity, float lf) { |
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loadFactor = lf; |
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setTable(new HashEntry[initialCapacity]); |
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} |
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|
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/** |
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* Set table to new HashEntry array. |
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* Call only while holding lock or in constructor. |
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**/ |
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void setTable(HashEntry[] newTable) { |
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threshold = (int)(newTable.length * loadFactor); |
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table = newTable; |
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} |
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|
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/** |
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* Return properly casted first entry of bin for given hash |
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*/ |
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HashEntry<K,V> getFirst(int hash) { |
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HashEntry[] tab = table; |
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return (HashEntry<K,V>) tab[hash & (tab.length - 1)]; |
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} |
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|
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/** |
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* Read value field of an entry under lock. Called if value |
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* field ever appears to be null. This is possible only if a |
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* compiler happens to reorder a HashEntry initialization with |
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* its table assignment, which is legal under memory model |
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* but is not known to ever occur. |
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*/ |
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V readValueUnderLock(HashEntry<K,V> e) { |
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lock(); |
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try { |
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return e.value; |
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} finally { |
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unlock(); |
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} |
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} |
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|
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/* Specialized implementations of map methods */ |
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|
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V get(Object key, int hash) { |
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if (count != 0) { // read-volatile |
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HashEntry<K,V> e = getFirst(hash); |
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while (e != null) { |
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if (e.hash == hash && key.equals(e.key)) { |
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V v = e.value; |
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if (v != null) |
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return v; |
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return readValueUnderLock(e); // recheck |
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} |
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e = e.next; |
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} |
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} |
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return null; |
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} |
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|
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boolean containsKey(Object key, int hash) { |
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if (count != 0) { // read-volatile |
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HashEntry<K,V> e = getFirst(hash); |
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while (e != null) { |
308 |
if (e.hash == hash && key.equals(e.key)) |
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return true; |
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e = e.next; |
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} |
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} |
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return false; |
314 |
} |
315 |
|
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boolean containsValue(Object value) { |
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if (count != 0) { // read-volatile |
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HashEntry[] tab = table; |
319 |
int len = tab.length; |
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for (int i = 0 ; i < len; i++) { |
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for (HashEntry<K,V> e = (HashEntry<K,V>)tab[i]; |
322 |
e != null ; |
323 |
e = e.next) { |
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V v = e.value; |
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if (v == null) // recheck |
326 |
v = readValueUnderLock(e); |
327 |
if (value.equals(v)) |
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return true; |
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} |
330 |
} |
331 |
} |
332 |
return false; |
333 |
} |
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|
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boolean replace(K key, int hash, V oldValue, V newValue) { |
336 |
lock(); |
337 |
try { |
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HashEntry<K,V> e = getFirst(hash); |
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while (e != null && (e.hash != hash || !key.equals(e.key))) |
340 |
e = e.next; |
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|
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boolean replaced = false; |
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if (e != null && oldValue.equals(e.value)) { |
344 |
replaced = true; |
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e.value = newValue; |
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} |
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return replaced; |
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} finally { |
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unlock(); |
350 |
} |
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} |
352 |
|
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V replace(K key, int hash, V newValue) { |
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lock(); |
355 |
try { |
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HashEntry<K,V> e = getFirst(hash); |
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while (e != null && (e.hash != hash || !key.equals(e.key))) |
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e = e.next; |
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|
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V oldValue = null; |
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if (e != null) { |
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oldValue = e.value; |
363 |
e.value = newValue; |
364 |
} |
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return oldValue; |
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} finally { |
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unlock(); |
368 |
} |
369 |
} |
370 |
|
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|
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V put(K key, int hash, V value, boolean onlyIfAbsent) { |
373 |
lock(); |
374 |
try { |
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int c = count; |
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if (c++ > threshold) // ensure capacity |
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rehash(); |
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HashEntry[] tab = table; |
379 |
int index = hash & (tab.length - 1); |
380 |
HashEntry<K,V> first = (HashEntry<K,V>) tab[index]; |
381 |
HashEntry<K,V> e = first; |
382 |
while (e != null && (e.hash != hash || !key.equals(e.key))) |
383 |
e = e.next; |
384 |
|
385 |
V oldValue; |
386 |
if (e != null) { |
387 |
oldValue = e.value; |
388 |
if (!onlyIfAbsent) |
389 |
e.value = value; |
390 |
} |
391 |
else { |
392 |
oldValue = null; |
393 |
++modCount; |
394 |
tab[index] = new HashEntry<K,V>(key, hash, first, value); |
395 |
count = c; // write-volatile |
396 |
} |
397 |
return oldValue; |
398 |
} finally { |
399 |
unlock(); |
400 |
} |
401 |
} |
402 |
|
403 |
void rehash() { |
404 |
HashEntry[] oldTable = table; |
405 |
int oldCapacity = oldTable.length; |
406 |
if (oldCapacity >= MAXIMUM_CAPACITY) |
407 |
return; |
408 |
|
409 |
/* |
410 |
* Reclassify nodes in each list to new Map. Because we are |
411 |
* using power-of-two expansion, the elements from each bin |
412 |
* must either stay at same index, or move with a power of two |
413 |
* offset. We eliminate unnecessary node creation by catching |
414 |
* cases where old nodes can be reused because their next |
415 |
* fields won't change. Statistically, at the default |
416 |
* threshold, only about one-sixth of them need cloning when |
417 |
* a table doubles. The nodes they replace will be garbage |
418 |
* collectable as soon as they are no longer referenced by any |
419 |
* reader thread that may be in the midst of traversing table |
420 |
* right now. |
421 |
*/ |
422 |
|
423 |
HashEntry[] newTable = new HashEntry[oldCapacity << 1]; |
424 |
threshold = (int)(newTable.length * loadFactor); |
425 |
int sizeMask = newTable.length - 1; |
426 |
for (int i = 0; i < oldCapacity ; i++) { |
427 |
// We need to guarantee that any existing reads of old Map can |
428 |
// proceed. So we cannot yet null out each bin. |
429 |
HashEntry<K,V> e = (HashEntry<K,V>)oldTable[i]; |
430 |
|
431 |
if (e != null) { |
432 |
HashEntry<K,V> next = e.next; |
433 |
int idx = e.hash & sizeMask; |
434 |
|
435 |
// Single node on list |
436 |
if (next == null) |
437 |
newTable[idx] = e; |
438 |
|
439 |
else { |
440 |
// Reuse trailing consecutive sequence at same slot |
441 |
HashEntry<K,V> lastRun = e; |
442 |
int lastIdx = idx; |
443 |
for (HashEntry<K,V> last = next; |
444 |
last != null; |
445 |
last = last.next) { |
446 |
int k = last.hash & sizeMask; |
447 |
if (k != lastIdx) { |
448 |
lastIdx = k; |
449 |
lastRun = last; |
450 |
} |
451 |
} |
452 |
newTable[lastIdx] = lastRun; |
453 |
|
454 |
// Clone all remaining nodes |
455 |
for (HashEntry<K,V> p = e; p != lastRun; p = p.next) { |
456 |
int k = p.hash & sizeMask; |
457 |
HashEntry<K,V> n = (HashEntry<K,V>)newTable[k]; |
458 |
newTable[k] = new HashEntry<K,V>(p.key, p.hash, |
459 |
n, p.value); |
460 |
} |
461 |
} |
462 |
} |
463 |
} |
464 |
table = newTable; |
465 |
} |
466 |
|
467 |
/** |
468 |
* Remove; match on key only if value null, else match both. |
469 |
*/ |
470 |
V remove(Object key, int hash, Object value) { |
471 |
lock(); |
472 |
try { |
473 |
int c = count - 1; |
474 |
HashEntry[] tab = table; |
475 |
int index = hash & (tab.length - 1); |
476 |
HashEntry<K,V> first = (HashEntry<K,V>)tab[index]; |
477 |
HashEntry<K,V> e = first; |
478 |
while (e != null && (e.hash != hash || !key.equals(e.key))) |
479 |
e = e.next; |
480 |
|
481 |
V oldValue = null; |
482 |
if (e != null) { |
483 |
V v = e.value; |
484 |
if (value == null || value.equals(v)) { |
485 |
oldValue = v; |
486 |
// All entries following removed node can stay |
487 |
// in list, but all preceding ones need to be |
488 |
// cloned. |
489 |
++modCount; |
490 |
HashEntry<K,V> newFirst = e.next; |
491 |
for (HashEntry<K,V> p = first; p != e; p = p.next) |
492 |
newFirst = new HashEntry<K,V>(p.key, p.hash, |
493 |
newFirst, p.value); |
494 |
tab[index] = newFirst; |
495 |
count = c; // write-volatile |
496 |
} |
497 |
} |
498 |
return oldValue; |
499 |
} finally { |
500 |
unlock(); |
501 |
} |
502 |
} |
503 |
|
504 |
void clear() { |
505 |
if (count != 0) { |
506 |
lock(); |
507 |
try { |
508 |
HashEntry[] tab = table; |
509 |
for (int i = 0; i < tab.length ; i++) |
510 |
tab[i] = null; |
511 |
++modCount; |
512 |
count = 0; // write-volatile |
513 |
} finally { |
514 |
unlock(); |
515 |
} |
516 |
} |
517 |
} |
518 |
} |
519 |
|
520 |
/** |
521 |
* ConcurrentHashMap list entry. Note that this is never exported |
522 |
* out as a user-visible Map.Entry |
523 |
*/ |
524 |
static final class HashEntry<K,V> { |
525 |
final K key; |
526 |
final int hash; |
527 |
volatile V value; |
528 |
final HashEntry<K,V> next; |
529 |
|
530 |
HashEntry(K key, int hash, HashEntry<K,V> next, V value) { |
531 |
this.key = key; |
532 |
this.hash = hash; |
533 |
this.next = next; |
534 |
this.value = value; |
535 |
} |
536 |
} |
537 |
|
538 |
|
539 |
/* ---------------- Public operations -------------- */ |
540 |
|
541 |
/** |
542 |
* Creates a new, empty map with the specified initial |
543 |
* capacity and the specified load factor. |
544 |
* |
545 |
* @param initialCapacity the initial capacity. The implementation |
546 |
* performs internal sizing to accommodate this many elements. |
547 |
* @param loadFactor the load factor threshold, used to control resizing. |
548 |
* @param concurrencyLevel the estimated number of concurrently |
549 |
* updating threads. The implementation performs internal sizing |
550 |
* to try to accommodate this many threads. |
551 |
* @throws IllegalArgumentException if the initial capacity is |
552 |
* negative or the load factor or concurrencyLevel are |
553 |
* nonpositive. |
554 |
*/ |
555 |
public ConcurrentHashMap(int initialCapacity, |
556 |
float loadFactor, int concurrencyLevel) { |
557 |
if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0) |
558 |
throw new IllegalArgumentException(); |
559 |
|
560 |
if (concurrencyLevel > MAX_SEGMENTS) |
561 |
concurrencyLevel = MAX_SEGMENTS; |
562 |
|
563 |
// Find power-of-two sizes best matching arguments |
564 |
int sshift = 0; |
565 |
int ssize = 1; |
566 |
while (ssize < concurrencyLevel) { |
567 |
++sshift; |
568 |
ssize <<= 1; |
569 |
} |
570 |
segmentShift = 32 - sshift; |
571 |
segmentMask = ssize - 1; |
572 |
this.segments = new Segment[ssize]; |
573 |
|
574 |
if (initialCapacity > MAXIMUM_CAPACITY) |
575 |
initialCapacity = MAXIMUM_CAPACITY; |
576 |
int c = initialCapacity / ssize; |
577 |
if (c * ssize < initialCapacity) |
578 |
++c; |
579 |
int cap = 1; |
580 |
while (cap < c) |
581 |
cap <<= 1; |
582 |
|
583 |
for (int i = 0; i < this.segments.length; ++i) |
584 |
this.segments[i] = new Segment<K,V>(cap, loadFactor); |
585 |
} |
586 |
|
587 |
/** |
588 |
* Creates a new, empty map with the specified initial |
589 |
* capacity, and with default load factor and concurrencyLevel. |
590 |
* |
591 |
* @param initialCapacity The implementation performs internal |
592 |
* sizing to accommodate this many elements. |
593 |
* @throws IllegalArgumentException if the initial capacity of |
594 |
* elements is negative. |
595 |
*/ |
596 |
public ConcurrentHashMap(int initialCapacity) { |
597 |
this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_SEGMENTS); |
598 |
} |
599 |
|
600 |
/** |
601 |
* Creates a new, empty map with a default initial capacity, |
602 |
* load factor, and concurrencyLevel. |
603 |
*/ |
604 |
public ConcurrentHashMap() { |
605 |
this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_SEGMENTS); |
606 |
} |
607 |
|
608 |
/** |
609 |
* Creates a new map with the same mappings as the given map. The |
610 |
* map is created with a capacity of twice the number of mappings in |
611 |
* the given map or 11 (whichever is greater), and a default load factor. |
612 |
* @param t the map |
613 |
*/ |
614 |
public ConcurrentHashMap(Map<? extends K, ? extends V> t) { |
615 |
this(Math.max((int) (t.size() / DEFAULT_LOAD_FACTOR) + 1, |
616 |
11), |
617 |
DEFAULT_LOAD_FACTOR, DEFAULT_SEGMENTS); |
618 |
putAll(t); |
619 |
} |
620 |
|
621 |
// inherit Map javadoc |
622 |
public boolean isEmpty() { |
623 |
final Segment[] segments = this.segments; |
624 |
/* |
625 |
* We keep track of per-segment modCounts to avoid ABA |
626 |
* problems in which an element in one segment was added and |
627 |
* in another removed during traversal, in which case the |
628 |
* table was never actually empty at any point. Note the |
629 |
* similar use of modCounts in the size() and containsValue() |
630 |
* methods, which are the only other methods also susceptible |
631 |
* to ABA problems. |
632 |
*/ |
633 |
int[] mc = new int[segments.length]; |
634 |
int mcsum = 0; |
635 |
for (int i = 0; i < segments.length; ++i) { |
636 |
if (segments[i].count != 0) |
637 |
return false; |
638 |
else |
639 |
mcsum += mc[i] = segments[i].modCount; |
640 |
} |
641 |
// If mcsum happens to be zero, then we know we got a snapshot |
642 |
// before any modifications at all were made. This is |
643 |
// probably common enough to bother tracking. |
644 |
if (mcsum != 0) { |
645 |
for (int i = 0; i < segments.length; ++i) { |
646 |
if (segments[i].count != 0 || |
647 |
mc[i] != segments[i].modCount) |
648 |
return false; |
649 |
} |
650 |
} |
651 |
return true; |
652 |
} |
653 |
|
654 |
// inherit Map javadoc |
655 |
public int size() { |
656 |
final Segment[] segments = this.segments; |
657 |
long sum = 0; |
658 |
long check = 0; |
659 |
int[] mc = new int[segments.length]; |
660 |
// Try at most twice to get accurate count. On failure due to |
661 |
// continuous async changes in table, resort to locking. |
662 |
for (int k = 0; k < 2; ++k) { |
663 |
check = 0; |
664 |
sum = 0; |
665 |
int mcsum = 0; |
666 |
for (int i = 0; i < segments.length; ++i) { |
667 |
sum += segments[i].count; |
668 |
mcsum += mc[i] = segments[i].modCount; |
669 |
} |
670 |
if (mcsum != 0) { |
671 |
for (int i = 0; i < segments.length; ++i) { |
672 |
check += segments[i].count; |
673 |
if (mc[i] != segments[i].modCount) { |
674 |
check = -1; // force retry |
675 |
break; |
676 |
} |
677 |
} |
678 |
} |
679 |
if (check == sum) |
680 |
break; |
681 |
} |
682 |
if (check != sum) { // Resort to locking all segments |
683 |
sum = 0; |
684 |
for (int i = 0; i < segments.length; ++i) |
685 |
segments[i].lock(); |
686 |
for (int i = 0; i < segments.length; ++i) |
687 |
sum += segments[i].count; |
688 |
for (int i = 0; i < segments.length; ++i) |
689 |
segments[i].unlock(); |
690 |
} |
691 |
if (sum > Integer.MAX_VALUE) |
692 |
return Integer.MAX_VALUE; |
693 |
else |
694 |
return (int)sum; |
695 |
} |
696 |
|
697 |
|
698 |
/** |
699 |
* Returns the value to which the specified key is mapped in this table. |
700 |
* |
701 |
* @param key a key in the table. |
702 |
* @return the value to which the key is mapped in this table; |
703 |
* <tt>null</tt> if the key is not mapped to any value in |
704 |
* this table. |
705 |
* @throws NullPointerException if the key is |
706 |
* <tt>null</tt>. |
707 |
*/ |
708 |
public V get(Object key) { |
709 |
int hash = hash(key); // throws NullPointerException if key null |
710 |
return segmentFor(hash).get(key, hash); |
711 |
} |
712 |
|
713 |
/** |
714 |
* Tests if the specified object is a key in this table. |
715 |
* |
716 |
* @param key possible key. |
717 |
* @return <tt>true</tt> if and only if the specified object |
718 |
* is a key in this table, as determined by the |
719 |
* <tt>equals</tt> method; <tt>false</tt> otherwise. |
720 |
* @throws NullPointerException if the key is |
721 |
* <tt>null</tt>. |
722 |
*/ |
723 |
public boolean containsKey(Object key) { |
724 |
int hash = hash(key); // throws NullPointerException if key null |
725 |
return segmentFor(hash).containsKey(key, hash); |
726 |
} |
727 |
|
728 |
/** |
729 |
* Returns <tt>true</tt> if this map maps one or more keys to the |
730 |
* specified value. Note: This method requires a full internal |
731 |
* traversal of the hash table, and so is much slower than |
732 |
* method <tt>containsKey</tt>. |
733 |
* |
734 |
* @param value value whose presence in this map is to be tested. |
735 |
* @return <tt>true</tt> if this map maps one or more keys to the |
736 |
* specified value. |
737 |
* @throws NullPointerException if the value is <tt>null</tt>. |
738 |
*/ |
739 |
public boolean containsValue(Object value) { |
740 |
if (value == null) |
741 |
throw new NullPointerException(); |
742 |
|
743 |
// See explanation of modCount use above |
744 |
|
745 |
final Segment[] segments = this.segments; |
746 |
int[] mc = new int[segments.length]; |
747 |
|
748 |
// Try at most twice without locking |
749 |
for (int k = 0; k < 2; ++k) { |
750 |
int sum = 0; |
751 |
int mcsum = 0; |
752 |
for (int i = 0; i < segments.length; ++i) { |
753 |
int c = segments[i].count; |
754 |
mcsum += mc[i] = segments[i].modCount; |
755 |
if (segments[i].containsValue(value)) |
756 |
return true; |
757 |
} |
758 |
boolean cleanSweep = true; |
759 |
if (mcsum != 0) { |
760 |
for (int i = 0; i < segments.length; ++i) { |
761 |
int c = segments[i].count; |
762 |
if (mc[i] != segments[i].modCount) { |
763 |
cleanSweep = false; |
764 |
break; |
765 |
} |
766 |
} |
767 |
} |
768 |
if (cleanSweep) |
769 |
return false; |
770 |
} |
771 |
// Resort to locking all segments |
772 |
for (int i = 0; i < segments.length; ++i) |
773 |
segments[i].lock(); |
774 |
boolean found = false; |
775 |
try { |
776 |
for (int i = 0; i < segments.length; ++i) { |
777 |
if (segments[i].containsValue(value)) { |
778 |
found = true; |
779 |
break; |
780 |
} |
781 |
} |
782 |
} finally { |
783 |
for (int i = 0; i < segments.length; ++i) |
784 |
segments[i].unlock(); |
785 |
} |
786 |
return found; |
787 |
} |
788 |
|
789 |
/** |
790 |
* Legacy method testing if some key maps into the specified value |
791 |
* in this table. This method is identical in functionality to |
792 |
* {@link #containsValue}, and exists solely to ensure |
793 |
* full compatibility with class {@link java.util.Hashtable}, |
794 |
* which supported this method prior to introduction of the |
795 |
* Java Collections framework. |
796 |
|
797 |
* @param value a value to search for. |
798 |
* @return <tt>true</tt> if and only if some key maps to the |
799 |
* <tt>value</tt> argument in this table as |
800 |
* determined by the <tt>equals</tt> method; |
801 |
* <tt>false</tt> otherwise. |
802 |
* @throws NullPointerException if the value is <tt>null</tt>. |
803 |
*/ |
804 |
public boolean contains(Object value) { |
805 |
return containsValue(value); |
806 |
} |
807 |
|
808 |
/** |
809 |
* Maps the specified <tt>key</tt> to the specified |
810 |
* <tt>value</tt> in this table. Neither the key nor the |
811 |
* value can be <tt>null</tt>. |
812 |
* |
813 |
* <p> The value can be retrieved by calling the <tt>get</tt> method |
814 |
* with a key that is equal to the original key. |
815 |
* |
816 |
* @param key the table key. |
817 |
* @param value the value. |
818 |
* @return the previous value of the specified key in this table, |
819 |
* or <tt>null</tt> if it did not have one. |
820 |
* @throws NullPointerException if the key or value is |
821 |
* <tt>null</tt>. |
822 |
*/ |
823 |
public V put(K key, V value) { |
824 |
if (value == null) |
825 |
throw new NullPointerException(); |
826 |
int hash = hash(key); |
827 |
return segmentFor(hash).put(key, hash, value, false); |
828 |
} |
829 |
|
830 |
/** |
831 |
* If the specified key is not already associated |
832 |
* with a value, associate it with the given value. |
833 |
* This is equivalent to |
834 |
* <pre> |
835 |
* if (!map.containsKey(key)) |
836 |
* return map.put(key, value); |
837 |
* else |
838 |
* return map.get(key); |
839 |
* </pre> |
840 |
* Except that the action is performed atomically. |
841 |
* @param key key with which the specified value is to be associated. |
842 |
* @param value value to be associated with the specified key. |
843 |
* @return previous value associated with specified key, or <tt>null</tt> |
844 |
* if there was no mapping for key. A <tt>null</tt> return can |
845 |
* also indicate that the map previously associated <tt>null</tt> |
846 |
* with the specified key, if the implementation supports |
847 |
* <tt>null</tt> values. |
848 |
* |
849 |
* @throws UnsupportedOperationException if the <tt>put</tt> operation is |
850 |
* not supported by this map. |
851 |
* @throws ClassCastException if the class of the specified key or value |
852 |
* prevents it from being stored in this map. |
853 |
* @throws NullPointerException if the specified key or value is |
854 |
* <tt>null</tt>. |
855 |
* |
856 |
**/ |
857 |
public V putIfAbsent(K key, V value) { |
858 |
if (value == null) |
859 |
throw new NullPointerException(); |
860 |
int hash = hash(key); |
861 |
return segmentFor(hash).put(key, hash, value, true); |
862 |
} |
863 |
|
864 |
|
865 |
/** |
866 |
* Copies all of the mappings from the specified map to this one. |
867 |
* |
868 |
* These mappings replace any mappings that this map had for any of the |
869 |
* keys currently in the specified Map. |
870 |
* |
871 |
* @param t Mappings to be stored in this map. |
872 |
*/ |
873 |
public void putAll(Map<? extends K, ? extends V> t) { |
874 |
for (Iterator<Map.Entry<? extends K, ? extends V>> it = (Iterator<Map.Entry<? extends K, ? extends V>>) t.entrySet().iterator(); it.hasNext(); ) { |
875 |
Entry<? extends K, ? extends V> e = it.next(); |
876 |
put(e.getKey(), e.getValue()); |
877 |
} |
878 |
} |
879 |
|
880 |
/** |
881 |
* Removes the key (and its corresponding value) from this |
882 |
* table. This method does nothing if the key is not in the table. |
883 |
* |
884 |
* @param key the key that needs to be removed. |
885 |
* @return the value to which the key had been mapped in this table, |
886 |
* or <tt>null</tt> if the key did not have a mapping. |
887 |
* @throws NullPointerException if the key is |
888 |
* <tt>null</tt>. |
889 |
*/ |
890 |
public V remove(Object key) { |
891 |
int hash = hash(key); |
892 |
return segmentFor(hash).remove(key, hash, null); |
893 |
} |
894 |
|
895 |
/** |
896 |
* Remove entry for key only if currently mapped to given value. |
897 |
* Acts as |
898 |
* <pre> |
899 |
* if (map.get(key).equals(value)) { |
900 |
* map.remove(key); |
901 |
* return true; |
902 |
* } else return false; |
903 |
* </pre> |
904 |
* except that the action is performed atomically. |
905 |
* @param key key with which the specified value is associated. |
906 |
* @param value value associated with the specified key. |
907 |
* @return true if the value was removed |
908 |
* @throws NullPointerException if the specified key is |
909 |
* <tt>null</tt>. |
910 |
*/ |
911 |
public boolean remove(Object key, Object value) { |
912 |
int hash = hash(key); |
913 |
return segmentFor(hash).remove(key, hash, value) != null; |
914 |
} |
915 |
|
916 |
|
917 |
/** |
918 |
* Replace entry for key only if currently mapped to given value. |
919 |
* Acts as |
920 |
* <pre> |
921 |
* if (map.get(key).equals(oldValue)) { |
922 |
* map.put(key, newValue); |
923 |
* return true; |
924 |
* } else return false; |
925 |
* </pre> |
926 |
* except that the action is performed atomically. |
927 |
* @param key key with which the specified value is associated. |
928 |
* @param oldValue value expected to be associated with the specified key. |
929 |
* @param newValue value to be associated with the specified key. |
930 |
* @return true if the value was replaced |
931 |
* @throws NullPointerException if the specified key or values are |
932 |
* <tt>null</tt>. |
933 |
*/ |
934 |
public boolean replace(K key, V oldValue, V newValue) { |
935 |
if (oldValue == null || newValue == null) |
936 |
throw new NullPointerException(); |
937 |
int hash = hash(key); |
938 |
return segmentFor(hash).replace(key, hash, oldValue, newValue); |
939 |
} |
940 |
|
941 |
/** |
942 |
* Replace entry for key only if currently mapped to some value. |
943 |
* Acts as |
944 |
* <pre> |
945 |
* if ((map.containsKey(key)) { |
946 |
* return map.put(key, value); |
947 |
* } else return null; |
948 |
* </pre> |
949 |
* except that the action is performed atomically. |
950 |
* @param key key with which the specified value is associated. |
951 |
* @param value value to be associated with the specified key. |
952 |
* @return previous value associated with specified key, or <tt>null</tt> |
953 |
* if there was no mapping for key. |
954 |
* @throws NullPointerException if the specified key or value is |
955 |
* <tt>null</tt>. |
956 |
*/ |
957 |
public V replace(K key, V value) { |
958 |
if (value == null) |
959 |
throw new NullPointerException(); |
960 |
int hash = hash(key); |
961 |
return segmentFor(hash).replace(key, hash, value); |
962 |
} |
963 |
|
964 |
|
965 |
/** |
966 |
* Removes all mappings from this map. |
967 |
*/ |
968 |
public void clear() { |
969 |
for (int i = 0; i < segments.length; ++i) |
970 |
segments[i].clear(); |
971 |
} |
972 |
|
973 |
|
974 |
/** |
975 |
* Returns a shallow copy of this |
976 |
* <tt>ConcurrentHashMap</tt> instance: the keys and |
977 |
* values themselves are not cloned. |
978 |
* |
979 |
* @return a shallow copy of this map. |
980 |
*/ |
981 |
public Object clone() { |
982 |
// We cannot call super.clone, since it would share final |
983 |
// segments array, and there's no way to reassign finals. |
984 |
|
985 |
float lf = segments[0].loadFactor; |
986 |
int segs = segments.length; |
987 |
int cap = (int)(size() / lf); |
988 |
if (cap < segs) cap = segs; |
989 |
ConcurrentHashMap<K,V> t = new ConcurrentHashMap<K,V>(cap, lf, segs); |
990 |
t.putAll(this); |
991 |
return t; |
992 |
} |
993 |
|
994 |
/** |
995 |
* Returns a set view of the keys contained in this map. The set is |
996 |
* backed by the map, so changes to the map are reflected in the set, and |
997 |
* vice-versa. The set supports element removal, which removes the |
998 |
* corresponding mapping from this map, via the <tt>Iterator.remove</tt>, |
999 |
* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and |
1000 |
* <tt>clear</tt> operations. It does not support the <tt>add</tt> or |
1001 |
* <tt>addAll</tt> operations. |
1002 |
* The returned <tt>iterator</tt> is a "weakly consistent" iterator that |
1003 |
* will never throw {@link java.util.ConcurrentModificationException}, |
1004 |
* 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 |
* |
1008 |
* @return a set view of the keys contained in this map. |
1009 |
*/ |
1010 |
public Set<K> keySet() { |
1011 |
Set<K> ks = keySet; |
1012 |
return (ks != null) ? ks : (keySet = new KeySet()); |
1013 |
} |
1014 |
|
1015 |
|
1016 |
/** |
1017 |
* Returns a collection view of the values contained in this map. The |
1018 |
* collection is backed by the map, so changes to the map are reflected in |
1019 |
* the collection, and vice-versa. The collection supports element |
1020 |
* removal, which removes the corresponding mapping from this map, via the |
1021 |
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>, |
1022 |
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations. |
1023 |
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations. |
1024 |
* The returned <tt>iterator</tt> is a "weakly consistent" iterator that |
1025 |
* will never throw {@link java.util.ConcurrentModificationException}, |
1026 |
* and guarantees to traverse elements as they existed upon |
1027 |
* construction of the iterator, and may (but is not guaranteed to) |
1028 |
* reflect any modifications subsequent to construction. |
1029 |
* |
1030 |
* @return a collection view of the values contained in this map. |
1031 |
*/ |
1032 |
public Collection<V> values() { |
1033 |
Collection<V> vs = values; |
1034 |
return (vs != null) ? vs : (values = new Values()); |
1035 |
} |
1036 |
|
1037 |
|
1038 |
/** |
1039 |
* Returns a collection view of the mappings contained in this map. Each |
1040 |
* element in the returned collection is a <tt>Map.Entry</tt>. The |
1041 |
* collection is backed by the map, so changes to the map are reflected in |
1042 |
* the collection, and vice-versa. The collection supports element |
1043 |
* removal, which removes the corresponding mapping from the map, via the |
1044 |
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>, |
1045 |
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations. |
1046 |
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations. |
1047 |
* The returned <tt>iterator</tt> is a "weakly consistent" iterator that |
1048 |
* will never throw {@link java.util.ConcurrentModificationException}, |
1049 |
* and guarantees to traverse elements as they existed upon |
1050 |
* construction of the iterator, and may (but is not guaranteed to) |
1051 |
* reflect any modifications subsequent to construction. |
1052 |
* |
1053 |
* @return a collection view of the mappings contained in this map. |
1054 |
*/ |
1055 |
public Set<Map.Entry<K,V>> entrySet() { |
1056 |
Set<Map.Entry<K,V>> es = entrySet; |
1057 |
return (es != null) ? es : (entrySet = (Set<Map.Entry<K,V>>) (Set) new EntrySet()); |
1058 |
} |
1059 |
|
1060 |
|
1061 |
/** |
1062 |
* Returns an enumeration of the keys in this table. |
1063 |
* |
1064 |
* @return an enumeration of the keys in this table. |
1065 |
* @see #keySet |
1066 |
*/ |
1067 |
public Enumeration<K> keys() { |
1068 |
return new KeyIterator(); |
1069 |
} |
1070 |
|
1071 |
/** |
1072 |
* Returns an enumeration of the values in this table. |
1073 |
* |
1074 |
* @return an enumeration of the values in this table. |
1075 |
* @see #values |
1076 |
*/ |
1077 |
public Enumeration<V> elements() { |
1078 |
return new ValueIterator(); |
1079 |
} |
1080 |
|
1081 |
/* ---------------- Iterator Support -------------- */ |
1082 |
|
1083 |
abstract class HashIterator { |
1084 |
int nextSegmentIndex; |
1085 |
int nextTableIndex; |
1086 |
HashEntry[] currentTable; |
1087 |
HashEntry<K, V> nextEntry; |
1088 |
HashEntry<K, V> lastReturned; |
1089 |
|
1090 |
HashIterator() { |
1091 |
nextSegmentIndex = segments.length - 1; |
1092 |
nextTableIndex = -1; |
1093 |
advance(); |
1094 |
} |
1095 |
|
1096 |
public boolean hasMoreElements() { return hasNext(); } |
1097 |
|
1098 |
final void advance() { |
1099 |
if (nextEntry != null && (nextEntry = nextEntry.next) != null) |
1100 |
return; |
1101 |
|
1102 |
while (nextTableIndex >= 0) { |
1103 |
if ( (nextEntry = (HashEntry<K,V>)currentTable[nextTableIndex--]) != null) |
1104 |
return; |
1105 |
} |
1106 |
|
1107 |
while (nextSegmentIndex >= 0) { |
1108 |
Segment<K,V> seg = (Segment<K,V>)segments[nextSegmentIndex--]; |
1109 |
if (seg.count != 0) { |
1110 |
currentTable = seg.table; |
1111 |
for (int j = currentTable.length - 1; j >= 0; --j) { |
1112 |
if ( (nextEntry = (HashEntry<K,V>)currentTable[j]) != null) { |
1113 |
nextTableIndex = j - 1; |
1114 |
return; |
1115 |
} |
1116 |
} |
1117 |
} |
1118 |
} |
1119 |
} |
1120 |
|
1121 |
public boolean hasNext() { return nextEntry != null; } |
1122 |
|
1123 |
HashEntry<K,V> nextEntry() { |
1124 |
if (nextEntry == null) |
1125 |
throw new NoSuchElementException(); |
1126 |
lastReturned = nextEntry; |
1127 |
advance(); |
1128 |
return lastReturned; |
1129 |
} |
1130 |
|
1131 |
public void remove() { |
1132 |
if (lastReturned == null) |
1133 |
throw new IllegalStateException(); |
1134 |
ConcurrentHashMap.this.remove(lastReturned.key); |
1135 |
lastReturned = null; |
1136 |
} |
1137 |
} |
1138 |
|
1139 |
final class KeyIterator extends HashIterator implements Iterator<K>, Enumeration<K> { |
1140 |
public K next() { return super.nextEntry().key; } |
1141 |
public K nextElement() { return super.nextEntry().key; } |
1142 |
} |
1143 |
|
1144 |
final class ValueIterator extends HashIterator implements Iterator<V>, Enumeration<V> { |
1145 |
public V next() { return super.nextEntry().value; } |
1146 |
public V nextElement() { return super.nextEntry().value; } |
1147 |
} |
1148 |
|
1149 |
|
1150 |
|
1151 |
/** |
1152 |
* Entry iterator. Exported Entry objects must write-through |
1153 |
* changes in setValue, even if the nodes have been cloned. So we |
1154 |
* cannot return internal HashEntry objects. Instead, the iterator |
1155 |
* itself acts as a forwarding pseudo-entry. |
1156 |
*/ |
1157 |
final class EntryIterator extends HashIterator implements Map.Entry<K,V>, Iterator<Entry<K,V>> { |
1158 |
public Map.Entry<K,V> next() { |
1159 |
nextEntry(); |
1160 |
return this; |
1161 |
} |
1162 |
|
1163 |
public K getKey() { |
1164 |
if (lastReturned == null) |
1165 |
throw new IllegalStateException("Entry was removed"); |
1166 |
return lastReturned.key; |
1167 |
} |
1168 |
|
1169 |
public V getValue() { |
1170 |
if (lastReturned == null) |
1171 |
throw new IllegalStateException("Entry was removed"); |
1172 |
return ConcurrentHashMap.this.get(lastReturned.key); |
1173 |
} |
1174 |
|
1175 |
public V setValue(V value) { |
1176 |
if (lastReturned == null) |
1177 |
throw new IllegalStateException("Entry was removed"); |
1178 |
return ConcurrentHashMap.this.put(lastReturned.key, value); |
1179 |
} |
1180 |
|
1181 |
public boolean equals(Object o) { |
1182 |
// If not acting as entry, just use default. |
1183 |
if (lastReturned == null) |
1184 |
return super.equals(o); |
1185 |
if (!(o instanceof Map.Entry)) |
1186 |
return false; |
1187 |
Map.Entry e = (Map.Entry)o; |
1188 |
return eq(getKey(), e.getKey()) && eq(getValue(), e.getValue()); |
1189 |
} |
1190 |
|
1191 |
public int hashCode() { |
1192 |
// If not acting as entry, just use default. |
1193 |
if (lastReturned == null) |
1194 |
return super.hashCode(); |
1195 |
|
1196 |
Object k = getKey(); |
1197 |
Object v = getValue(); |
1198 |
return ((k == null) ? 0 : k.hashCode()) ^ |
1199 |
((v == null) ? 0 : v.hashCode()); |
1200 |
} |
1201 |
|
1202 |
public String toString() { |
1203 |
// If not acting as entry, just use default. |
1204 |
if (lastReturned == null) |
1205 |
return super.toString(); |
1206 |
else |
1207 |
return getKey() + "=" + getValue(); |
1208 |
} |
1209 |
|
1210 |
boolean eq(Object o1, Object o2) { |
1211 |
return (o1 == null ? o2 == null : o1.equals(o2)); |
1212 |
} |
1213 |
|
1214 |
} |
1215 |
|
1216 |
final class KeySet extends AbstractSet<K> { |
1217 |
public Iterator<K> iterator() { |
1218 |
return new KeyIterator(); |
1219 |
} |
1220 |
public int size() { |
1221 |
return ConcurrentHashMap.this.size(); |
1222 |
} |
1223 |
public boolean contains(Object o) { |
1224 |
return ConcurrentHashMap.this.containsKey(o); |
1225 |
} |
1226 |
public boolean remove(Object o) { |
1227 |
return ConcurrentHashMap.this.remove(o) != null; |
1228 |
} |
1229 |
public void clear() { |
1230 |
ConcurrentHashMap.this.clear(); |
1231 |
} |
1232 |
} |
1233 |
|
1234 |
final class Values extends AbstractCollection<V> { |
1235 |
public Iterator<V> iterator() { |
1236 |
return new ValueIterator(); |
1237 |
} |
1238 |
public int size() { |
1239 |
return ConcurrentHashMap.this.size(); |
1240 |
} |
1241 |
public boolean contains(Object o) { |
1242 |
return ConcurrentHashMap.this.containsValue(o); |
1243 |
} |
1244 |
public void clear() { |
1245 |
ConcurrentHashMap.this.clear(); |
1246 |
} |
1247 |
} |
1248 |
|
1249 |
final class EntrySet extends AbstractSet<Map.Entry<K,V>> { |
1250 |
public Iterator<Map.Entry<K,V>> iterator() { |
1251 |
return new EntryIterator(); |
1252 |
} |
1253 |
public boolean contains(Object o) { |
1254 |
if (!(o instanceof Map.Entry)) |
1255 |
return false; |
1256 |
Map.Entry<K,V> e = (Map.Entry<K,V>)o; |
1257 |
V v = ConcurrentHashMap.this.get(e.getKey()); |
1258 |
return v != null && v.equals(e.getValue()); |
1259 |
} |
1260 |
public boolean remove(Object o) { |
1261 |
if (!(o instanceof Map.Entry)) |
1262 |
return false; |
1263 |
Map.Entry<K,V> e = (Map.Entry<K,V>)o; |
1264 |
return ConcurrentHashMap.this.remove(e.getKey(), e.getValue()); |
1265 |
} |
1266 |
public int size() { |
1267 |
return ConcurrentHashMap.this.size(); |
1268 |
} |
1269 |
public void clear() { |
1270 |
ConcurrentHashMap.this.clear(); |
1271 |
} |
1272 |
public Object[] toArray() { |
1273 |
// Since we don't ordinarily have distinct Entry objects, we |
1274 |
// must pack elements using exportable SimpleEntry |
1275 |
Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>(size()); |
1276 |
for (Iterator<Map.Entry<K,V>> i = iterator(); i.hasNext(); ) |
1277 |
c.add(new SimpleEntry<K,V>(i.next())); |
1278 |
return c.toArray(); |
1279 |
} |
1280 |
public <T> T[] toArray(T[] a) { |
1281 |
Collection<Map.Entry<K,V>> c = new ArrayList<Map.Entry<K,V>>(size()); |
1282 |
for (Iterator<Map.Entry<K,V>> i = iterator(); i.hasNext(); ) |
1283 |
c.add(new SimpleEntry<K,V>(i.next())); |
1284 |
return c.toArray(a); |
1285 |
} |
1286 |
|
1287 |
} |
1288 |
|
1289 |
/** |
1290 |
* This duplicates java.util.AbstractMap.SimpleEntry until this class |
1291 |
* is made accessible. |
1292 |
*/ |
1293 |
static final class SimpleEntry<K,V> implements Entry<K,V> { |
1294 |
K key; |
1295 |
V value; |
1296 |
|
1297 |
public SimpleEntry(K key, V value) { |
1298 |
this.key = key; |
1299 |
this.value = value; |
1300 |
} |
1301 |
|
1302 |
public SimpleEntry(Entry<K,V> e) { |
1303 |
this.key = e.getKey(); |
1304 |
this.value = e.getValue(); |
1305 |
} |
1306 |
|
1307 |
public K getKey() { |
1308 |
return key; |
1309 |
} |
1310 |
|
1311 |
public V getValue() { |
1312 |
return value; |
1313 |
} |
1314 |
|
1315 |
public V setValue(V value) { |
1316 |
V oldValue = this.value; |
1317 |
this.value = value; |
1318 |
return oldValue; |
1319 |
} |
1320 |
|
1321 |
public boolean equals(Object o) { |
1322 |
if (!(o instanceof Map.Entry)) |
1323 |
return false; |
1324 |
Map.Entry e = (Map.Entry)o; |
1325 |
return eq(key, e.getKey()) && eq(value, e.getValue()); |
1326 |
} |
1327 |
|
1328 |
public int hashCode() { |
1329 |
return ((key == null) ? 0 : key.hashCode()) ^ |
1330 |
((value == null) ? 0 : value.hashCode()); |
1331 |
} |
1332 |
|
1333 |
public String toString() { |
1334 |
return key + "=" + value; |
1335 |
} |
1336 |
|
1337 |
static boolean eq(Object o1, Object o2) { |
1338 |
return (o1 == null ? o2 == null : o1.equals(o2)); |
1339 |
} |
1340 |
} |
1341 |
|
1342 |
/* ---------------- Serialization Support -------------- */ |
1343 |
|
1344 |
/** |
1345 |
* Save the state of the <tt>ConcurrentHashMap</tt> |
1346 |
* instance to a stream (i.e., |
1347 |
* serialize it). |
1348 |
* @param s the stream |
1349 |
* @serialData |
1350 |
* the key (Object) and value (Object) |
1351 |
* for each key-value mapping, followed by a null pair. |
1352 |
* The key-value mappings are emitted in no particular order. |
1353 |
*/ |
1354 |
private void writeObject(java.io.ObjectOutputStream s) throws IOException { |
1355 |
s.defaultWriteObject(); |
1356 |
|
1357 |
for (int k = 0; k < segments.length; ++k) { |
1358 |
Segment<K,V> seg = (Segment<K,V>)segments[k]; |
1359 |
seg.lock(); |
1360 |
try { |
1361 |
HashEntry[] tab = seg.table; |
1362 |
for (int i = 0; i < tab.length; ++i) { |
1363 |
for (HashEntry<K,V> e = (HashEntry<K,V>)tab[i]; e != null; e = e.next) { |
1364 |
s.writeObject(e.key); |
1365 |
s.writeObject(e.value); |
1366 |
} |
1367 |
} |
1368 |
} finally { |
1369 |
seg.unlock(); |
1370 |
} |
1371 |
} |
1372 |
s.writeObject(null); |
1373 |
s.writeObject(null); |
1374 |
} |
1375 |
|
1376 |
/** |
1377 |
* Reconstitute the <tt>ConcurrentHashMap</tt> |
1378 |
* instance from a stream (i.e., |
1379 |
* deserialize it). |
1380 |
* @param s the stream |
1381 |
*/ |
1382 |
private void readObject(java.io.ObjectInputStream s) |
1383 |
throws IOException, ClassNotFoundException { |
1384 |
s.defaultReadObject(); |
1385 |
|
1386 |
// Initialize each segment to be minimally sized, and let grow. |
1387 |
for (int i = 0; i < segments.length; ++i) { |
1388 |
segments[i].setTable(new HashEntry[1]); |
1389 |
} |
1390 |
|
1391 |
// Read the keys and values, and put the mappings in the table |
1392 |
for (;;) { |
1393 |
K key = (K) s.readObject(); |
1394 |
V value = (V) s.readObject(); |
1395 |
if (key == null) |
1396 |
break; |
1397 |
put(key, value); |
1398 |
} |
1399 |
} |
1400 |
} |
1401 |
|