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jeremybenn |
/*
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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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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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* 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 {@link ConcurrentModificationException}.
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* However, iterators are 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 <tt>16</tt>), 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 Hashtable} but unlike {@link HashMap}, this class
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* does <em>not</em> allow <tt>null</tt> to be 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}/../technotes/guides/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>, Serializable {
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private static final long serialVersionUID = 7249069246763182397L;
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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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/* ---------------- Constants -------------- */
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/**
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* The default initial capacity for this table,
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* used when not otherwise specified in a constructor.
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*/
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static final int DEFAULT_INITIAL_CAPACITY = 16;
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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 a 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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* The default concurrency level for this table, used when not
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* otherwise specified in a constructor.
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*/
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static final int DEFAULT_CONCURRENCY_LEVEL = 16;
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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 indexable
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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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* 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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* Number of unsynchronized retries in size and containsValue
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* methods before resorting to locking. This is used to avoid
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* unbounded retries if tables undergo continuous modification
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* which would make it impossible to obtain an accurate result.
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*/
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static final int RETRIES_BEFORE_LOCK = 2;
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/* ---------------- Fields -------------- */
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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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* 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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* The segments, each of which is a specialized hash table
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*/
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final Segment<K,V>[] segments;
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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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/* ---------------- Small Utilities -------------- */
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/**
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* Applies a supplemental hash function to a given hashCode, which
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* defends against poor quality hash functions. This is critical
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* because ConcurrentHashMap uses power-of-two length hash tables,
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* that otherwise encounter collisions for hashCodes that do not
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* differ in lower bits.
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*/
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private static int hash(int h) {
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// This function ensures that hashCodes that differ only by
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// constant multiples at each bit position have a bounded
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// number of collisions (approximately 8 at default load factor).
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h ^= (h >>> 20) ^ (h >>> 12);
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return h ^ (h >>> 7) ^ (h >>> 4);
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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 segments[(hash >>> segmentShift) & segmentMask];
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}
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/* ---------------- Inner Classes -------------- */
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/**
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* ConcurrentHashMap list entry. Note that this is never exported
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* out as a user-visible Map.Entry.
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*
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* Because the value field is volatile, not final, it is legal wrt
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* the Java Memory Model for an unsynchronized reader to see null
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* instead of initial value when read via a data race. Although a
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* reordering leading to this is not likely to ever actually
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* occur, the Segment.readValueUnderLock method is used as a
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* backup in case a null (pre-initialized) value is ever seen in
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* an unsynchronized access method.
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*/
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static final class HashEntry<K,V> {
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final K key;
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final int hash;
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volatile V value;
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final HashEntry<K,V> next;
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HashEntry(K key, int hash, HashEntry<K,V> next, V value) {
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this.key = key;
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this.hash = hash;
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this.next = next;
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this.value = value;
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}
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@SuppressWarnings("unchecked")
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static final <K,V> HashEntry<K,V>[] newArray(int i) {
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return new HashEntry[i];
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}
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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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private static final long serialVersionUID = 2249069246763182397L;
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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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* 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 containsValue, 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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* The table is rehashed when its size exceeds this threshold.
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* (The value of this field is always <tt>(int)(capacity *
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* loadFactor)</tt>.)
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*/
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transient int threshold;
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/**
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* The per-segment table.
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*/
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transient volatile HashEntry<K,V>[] table;
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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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Segment(int initialCapacity, float lf) {
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loadFactor = lf;
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setTable(HashEntry.<K,V>newArray(initialCapacity));
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}
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@SuppressWarnings("unchecked")
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static final <K,V> Segment<K,V>[] newArray(int i) {
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return new Segment[i];
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}
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/**
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* Sets 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<K,V>[] 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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* Returns 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<K,V>[] tab = table;
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return tab[hash & (tab.length - 1)];
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}
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/**
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* Reads 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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/* Specialized implementations of map methods */
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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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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) {
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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;
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}
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357 |
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|
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boolean containsValue(Object value) {
|
359 |
|
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if (count != 0) { // read-volatile
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|
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HashEntry<K,V>[] tab = table;
|
361 |
|
|
int len = tab.length;
|
362 |
|
|
for (int i = 0 ; i < len; i++) {
|
363 |
|
|
for (HashEntry<K,V> e = tab[i]; e != null; e = e.next) {
|
364 |
|
|
V v = e.value;
|
365 |
|
|
if (v == null) // recheck
|
366 |
|
|
v = readValueUnderLock(e);
|
367 |
|
|
if (value.equals(v))
|
368 |
|
|
return true;
|
369 |
|
|
}
|
370 |
|
|
}
|
371 |
|
|
}
|
372 |
|
|
return false;
|
373 |
|
|
}
|
374 |
|
|
|
375 |
|
|
boolean replace(K key, int hash, V oldValue, V newValue) {
|
376 |
|
|
lock();
|
377 |
|
|
try {
|
378 |
|
|
HashEntry<K,V> e = getFirst(hash);
|
379 |
|
|
while (e != null && (e.hash != hash || !key.equals(e.key)))
|
380 |
|
|
e = e.next;
|
381 |
|
|
|
382 |
|
|
boolean replaced = false;
|
383 |
|
|
if (e != null && oldValue.equals(e.value)) {
|
384 |
|
|
replaced = true;
|
385 |
|
|
e.value = newValue;
|
386 |
|
|
}
|
387 |
|
|
return replaced;
|
388 |
|
|
} finally {
|
389 |
|
|
unlock();
|
390 |
|
|
}
|
391 |
|
|
}
|
392 |
|
|
|
393 |
|
|
V replace(K key, int hash, V newValue) {
|
394 |
|
|
lock();
|
395 |
|
|
try {
|
396 |
|
|
HashEntry<K,V> e = getFirst(hash);
|
397 |
|
|
while (e != null && (e.hash != hash || !key.equals(e.key)))
|
398 |
|
|
e = e.next;
|
399 |
|
|
|
400 |
|
|
V oldValue = null;
|
401 |
|
|
if (e != null) {
|
402 |
|
|
oldValue = e.value;
|
403 |
|
|
e.value = newValue;
|
404 |
|
|
}
|
405 |
|
|
return oldValue;
|
406 |
|
|
} finally {
|
407 |
|
|
unlock();
|
408 |
|
|
}
|
409 |
|
|
}
|
410 |
|
|
|
411 |
|
|
|
412 |
|
|
V put(K key, int hash, V value, boolean onlyIfAbsent) {
|
413 |
|
|
lock();
|
414 |
|
|
try {
|
415 |
|
|
int c = count;
|
416 |
|
|
if (c++ > threshold) // ensure capacity
|
417 |
|
|
rehash();
|
418 |
|
|
HashEntry<K,V>[] tab = table;
|
419 |
|
|
int index = hash & (tab.length - 1);
|
420 |
|
|
HashEntry<K,V> first = tab[index];
|
421 |
|
|
HashEntry<K,V> e = first;
|
422 |
|
|
while (e != null && (e.hash != hash || !key.equals(e.key)))
|
423 |
|
|
e = e.next;
|
424 |
|
|
|
425 |
|
|
V oldValue;
|
426 |
|
|
if (e != null) {
|
427 |
|
|
oldValue = e.value;
|
428 |
|
|
if (!onlyIfAbsent)
|
429 |
|
|
e.value = value;
|
430 |
|
|
}
|
431 |
|
|
else {
|
432 |
|
|
oldValue = null;
|
433 |
|
|
++modCount;
|
434 |
|
|
tab[index] = new HashEntry<K,V>(key, hash, first, value);
|
435 |
|
|
count = c; // write-volatile
|
436 |
|
|
}
|
437 |
|
|
return oldValue;
|
438 |
|
|
} finally {
|
439 |
|
|
unlock();
|
440 |
|
|
}
|
441 |
|
|
}
|
442 |
|
|
|
443 |
|
|
void rehash() {
|
444 |
|
|
HashEntry<K,V>[] oldTable = table;
|
445 |
|
|
int oldCapacity = oldTable.length;
|
446 |
|
|
if (oldCapacity >= MAXIMUM_CAPACITY)
|
447 |
|
|
return;
|
448 |
|
|
|
449 |
|
|
/*
|
450 |
|
|
* Reclassify nodes in each list to new Map. Because we are
|
451 |
|
|
* using power-of-two expansion, the elements from each bin
|
452 |
|
|
* must either stay at same index, or move with a power of two
|
453 |
|
|
* offset. We eliminate unnecessary node creation by catching
|
454 |
|
|
* cases where old nodes can be reused because their next
|
455 |
|
|
* fields won't change. Statistically, at the default
|
456 |
|
|
* threshold, only about one-sixth of them need cloning when
|
457 |
|
|
* a table doubles. The nodes they replace will be garbage
|
458 |
|
|
* collectable as soon as they are no longer referenced by any
|
459 |
|
|
* reader thread that may be in the midst of traversing table
|
460 |
|
|
* right now.
|
461 |
|
|
*/
|
462 |
|
|
|
463 |
|
|
HashEntry<K,V>[] newTable = HashEntry.newArray(oldCapacity<<1);
|
464 |
|
|
threshold = (int)(newTable.length * loadFactor);
|
465 |
|
|
int sizeMask = newTable.length - 1;
|
466 |
|
|
for (int i = 0; i < oldCapacity ; i++) {
|
467 |
|
|
// We need to guarantee that any existing reads of old Map can
|
468 |
|
|
// proceed. So we cannot yet null out each bin.
|
469 |
|
|
HashEntry<K,V> e = oldTable[i];
|
470 |
|
|
|
471 |
|
|
if (e != null) {
|
472 |
|
|
HashEntry<K,V> next = e.next;
|
473 |
|
|
int idx = e.hash & sizeMask;
|
474 |
|
|
|
475 |
|
|
// Single node on list
|
476 |
|
|
if (next == null)
|
477 |
|
|
newTable[idx] = e;
|
478 |
|
|
|
479 |
|
|
else {
|
480 |
|
|
// Reuse trailing consecutive sequence at same slot
|
481 |
|
|
HashEntry<K,V> lastRun = e;
|
482 |
|
|
int lastIdx = idx;
|
483 |
|
|
for (HashEntry<K,V> last = next;
|
484 |
|
|
last != null;
|
485 |
|
|
last = last.next) {
|
486 |
|
|
int k = last.hash & sizeMask;
|
487 |
|
|
if (k != lastIdx) {
|
488 |
|
|
lastIdx = k;
|
489 |
|
|
lastRun = last;
|
490 |
|
|
}
|
491 |
|
|
}
|
492 |
|
|
newTable[lastIdx] = lastRun;
|
493 |
|
|
|
494 |
|
|
// Clone all remaining nodes
|
495 |
|
|
for (HashEntry<K,V> p = e; p != lastRun; p = p.next) {
|
496 |
|
|
int k = p.hash & sizeMask;
|
497 |
|
|
HashEntry<K,V> n = newTable[k];
|
498 |
|
|
newTable[k] = new HashEntry<K,V>(p.key, p.hash,
|
499 |
|
|
n, p.value);
|
500 |
|
|
}
|
501 |
|
|
}
|
502 |
|
|
}
|
503 |
|
|
}
|
504 |
|
|
table = newTable;
|
505 |
|
|
}
|
506 |
|
|
|
507 |
|
|
/**
|
508 |
|
|
* Remove; match on key only if value null, else match both.
|
509 |
|
|
*/
|
510 |
|
|
V remove(Object key, int hash, Object value) {
|
511 |
|
|
lock();
|
512 |
|
|
try {
|
513 |
|
|
int c = count - 1;
|
514 |
|
|
HashEntry<K,V>[] tab = table;
|
515 |
|
|
int index = hash & (tab.length - 1);
|
516 |
|
|
HashEntry<K,V> first = tab[index];
|
517 |
|
|
HashEntry<K,V> e = first;
|
518 |
|
|
while (e != null && (e.hash != hash || !key.equals(e.key)))
|
519 |
|
|
e = e.next;
|
520 |
|
|
|
521 |
|
|
V oldValue = null;
|
522 |
|
|
if (e != null) {
|
523 |
|
|
V v = e.value;
|
524 |
|
|
if (value == null || value.equals(v)) {
|
525 |
|
|
oldValue = v;
|
526 |
|
|
// All entries following removed node can stay
|
527 |
|
|
// in list, but all preceding ones need to be
|
528 |
|
|
// cloned.
|
529 |
|
|
++modCount;
|
530 |
|
|
HashEntry<K,V> newFirst = e.next;
|
531 |
|
|
for (HashEntry<K,V> p = first; p != e; p = p.next)
|
532 |
|
|
newFirst = new HashEntry<K,V>(p.key, p.hash,
|
533 |
|
|
newFirst, p.value);
|
534 |
|
|
tab[index] = newFirst;
|
535 |
|
|
count = c; // write-volatile
|
536 |
|
|
}
|
537 |
|
|
}
|
538 |
|
|
return oldValue;
|
539 |
|
|
} finally {
|
540 |
|
|
unlock();
|
541 |
|
|
}
|
542 |
|
|
}
|
543 |
|
|
|
544 |
|
|
void clear() {
|
545 |
|
|
if (count != 0) {
|
546 |
|
|
lock();
|
547 |
|
|
try {
|
548 |
|
|
HashEntry<K,V>[] tab = table;
|
549 |
|
|
for (int i = 0; i < tab.length ; i++)
|
550 |
|
|
tab[i] = null;
|
551 |
|
|
++modCount;
|
552 |
|
|
count = 0; // write-volatile
|
553 |
|
|
} finally {
|
554 |
|
|
unlock();
|
555 |
|
|
}
|
556 |
|
|
}
|
557 |
|
|
}
|
558 |
|
|
}
|
559 |
|
|
|
560 |
|
|
|
561 |
|
|
|
562 |
|
|
/* ---------------- Public operations -------------- */
|
563 |
|
|
|
564 |
|
|
/**
|
565 |
|
|
* Creates a new, empty map with the specified initial
|
566 |
|
|
* capacity, load factor and concurrency level.
|
567 |
|
|
*
|
568 |
|
|
* @param initialCapacity the initial capacity. The implementation
|
569 |
|
|
* performs internal sizing to accommodate this many elements.
|
570 |
|
|
* @param loadFactor the load factor threshold, used to control resizing.
|
571 |
|
|
* Resizing may be performed when the average number of elements per
|
572 |
|
|
* bin exceeds this threshold.
|
573 |
|
|
* @param concurrencyLevel the estimated number of concurrently
|
574 |
|
|
* updating threads. The implementation performs internal sizing
|
575 |
|
|
* to try to accommodate this many threads.
|
576 |
|
|
* @throws IllegalArgumentException if the initial capacity is
|
577 |
|
|
* negative or the load factor or concurrencyLevel are
|
578 |
|
|
* nonpositive.
|
579 |
|
|
*/
|
580 |
|
|
public ConcurrentHashMap(int initialCapacity,
|
581 |
|
|
float loadFactor, int concurrencyLevel) {
|
582 |
|
|
if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0)
|
583 |
|
|
throw new IllegalArgumentException();
|
584 |
|
|
|
585 |
|
|
if (concurrencyLevel > MAX_SEGMENTS)
|
586 |
|
|
concurrencyLevel = MAX_SEGMENTS;
|
587 |
|
|
|
588 |
|
|
// Find power-of-two sizes best matching arguments
|
589 |
|
|
int sshift = 0;
|
590 |
|
|
int ssize = 1;
|
591 |
|
|
while (ssize < concurrencyLevel) {
|
592 |
|
|
++sshift;
|
593 |
|
|
ssize <<= 1;
|
594 |
|
|
}
|
595 |
|
|
segmentShift = 32 - sshift;
|
596 |
|
|
segmentMask = ssize - 1;
|
597 |
|
|
this.segments = Segment.newArray(ssize);
|
598 |
|
|
|
599 |
|
|
if (initialCapacity > MAXIMUM_CAPACITY)
|
600 |
|
|
initialCapacity = MAXIMUM_CAPACITY;
|
601 |
|
|
int c = initialCapacity / ssize;
|
602 |
|
|
if (c * ssize < initialCapacity)
|
603 |
|
|
++c;
|
604 |
|
|
int cap = 1;
|
605 |
|
|
while (cap < c)
|
606 |
|
|
cap <<= 1;
|
607 |
|
|
|
608 |
|
|
for (int i = 0; i < this.segments.length; ++i)
|
609 |
|
|
this.segments[i] = new Segment<K,V>(cap, loadFactor);
|
610 |
|
|
}
|
611 |
|
|
|
612 |
|
|
/**
|
613 |
|
|
* Creates a new, empty map with the specified initial capacity
|
614 |
|
|
* and load factor and with the default concurrencyLevel (16).
|
615 |
|
|
*
|
616 |
|
|
* @param initialCapacity The implementation performs internal
|
617 |
|
|
* sizing to accommodate this many elements.
|
618 |
|
|
* @param loadFactor the load factor threshold, used to control resizing.
|
619 |
|
|
* Resizing may be performed when the average number of elements per
|
620 |
|
|
* bin exceeds this threshold.
|
621 |
|
|
* @throws IllegalArgumentException if the initial capacity of
|
622 |
|
|
* elements is negative or the load factor is nonpositive
|
623 |
|
|
*
|
624 |
|
|
* @since 1.6
|
625 |
|
|
*/
|
626 |
|
|
public ConcurrentHashMap(int initialCapacity, float loadFactor) {
|
627 |
|
|
this(initialCapacity, loadFactor, DEFAULT_CONCURRENCY_LEVEL);
|
628 |
|
|
}
|
629 |
|
|
|
630 |
|
|
/**
|
631 |
|
|
* Creates a new, empty map with the specified initial capacity,
|
632 |
|
|
* and with default load factor (0.75) and concurrencyLevel (16).
|
633 |
|
|
*
|
634 |
|
|
* @param initialCapacity the initial capacity. The implementation
|
635 |
|
|
* performs internal sizing to accommodate this many elements.
|
636 |
|
|
* @throws IllegalArgumentException if the initial capacity of
|
637 |
|
|
* elements is negative.
|
638 |
|
|
*/
|
639 |
|
|
public ConcurrentHashMap(int initialCapacity) {
|
640 |
|
|
this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
|
641 |
|
|
}
|
642 |
|
|
|
643 |
|
|
/**
|
644 |
|
|
* Creates a new, empty map with a default initial capacity (16),
|
645 |
|
|
* load factor (0.75) and concurrencyLevel (16).
|
646 |
|
|
*/
|
647 |
|
|
public ConcurrentHashMap() {
|
648 |
|
|
this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
|
649 |
|
|
}
|
650 |
|
|
|
651 |
|
|
/**
|
652 |
|
|
* Creates a new map with the same mappings as the given map.
|
653 |
|
|
* The map is created with a capacity of 1.5 times the number
|
654 |
|
|
* of mappings in the given map or 16 (whichever is greater),
|
655 |
|
|
* and a default load factor (0.75) and concurrencyLevel (16).
|
656 |
|
|
*
|
657 |
|
|
* @param m the map
|
658 |
|
|
*/
|
659 |
|
|
public ConcurrentHashMap(Map<? extends K, ? extends V> m) {
|
660 |
|
|
this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
|
661 |
|
|
DEFAULT_INITIAL_CAPACITY),
|
662 |
|
|
DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
|
663 |
|
|
putAll(m);
|
664 |
|
|
}
|
665 |
|
|
|
666 |
|
|
/**
|
667 |
|
|
* Returns <tt>true</tt> if this map contains no key-value mappings.
|
668 |
|
|
*
|
669 |
|
|
* @return <tt>true</tt> if this map contains no key-value mappings
|
670 |
|
|
*/
|
671 |
|
|
public boolean isEmpty() {
|
672 |
|
|
final Segment<K,V>[] segments = this.segments;
|
673 |
|
|
/*
|
674 |
|
|
* We keep track of per-segment modCounts to avoid ABA
|
675 |
|
|
* problems in which an element in one segment was added and
|
676 |
|
|
* in another removed during traversal, in which case the
|
677 |
|
|
* table was never actually empty at any point. Note the
|
678 |
|
|
* similar use of modCounts in the size() and containsValue()
|
679 |
|
|
* methods, which are the only other methods also susceptible
|
680 |
|
|
* to ABA problems.
|
681 |
|
|
*/
|
682 |
|
|
int[] mc = new int[segments.length];
|
683 |
|
|
int mcsum = 0;
|
684 |
|
|
for (int i = 0; i < segments.length; ++i) {
|
685 |
|
|
if (segments[i].count != 0)
|
686 |
|
|
return false;
|
687 |
|
|
else
|
688 |
|
|
mcsum += mc[i] = segments[i].modCount;
|
689 |
|
|
}
|
690 |
|
|
// If mcsum happens to be zero, then we know we got a snapshot
|
691 |
|
|
// before any modifications at all were made. This is
|
692 |
|
|
// probably common enough to bother tracking.
|
693 |
|
|
if (mcsum != 0) {
|
694 |
|
|
for (int i = 0; i < segments.length; ++i) {
|
695 |
|
|
if (segments[i].count != 0 ||
|
696 |
|
|
mc[i] != segments[i].modCount)
|
697 |
|
|
return false;
|
698 |
|
|
}
|
699 |
|
|
}
|
700 |
|
|
return true;
|
701 |
|
|
}
|
702 |
|
|
|
703 |
|
|
/**
|
704 |
|
|
* Returns the number of key-value mappings in this map. If the
|
705 |
|
|
* map contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
|
706 |
|
|
* <tt>Integer.MAX_VALUE</tt>.
|
707 |
|
|
*
|
708 |
|
|
* @return the number of key-value mappings in this map
|
709 |
|
|
*/
|
710 |
|
|
public int size() {
|
711 |
|
|
final Segment<K,V>[] segments = this.segments;
|
712 |
|
|
long sum = 0;
|
713 |
|
|
long check = 0;
|
714 |
|
|
int[] mc = new int[segments.length];
|
715 |
|
|
// Try a few times to get accurate count. On failure due to
|
716 |
|
|
// continuous async changes in table, resort to locking.
|
717 |
|
|
for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) {
|
718 |
|
|
check = 0;
|
719 |
|
|
sum = 0;
|
720 |
|
|
int mcsum = 0;
|
721 |
|
|
for (int i = 0; i < segments.length; ++i) {
|
722 |
|
|
sum += segments[i].count;
|
723 |
|
|
mcsum += mc[i] = segments[i].modCount;
|
724 |
|
|
}
|
725 |
|
|
if (mcsum != 0) {
|
726 |
|
|
for (int i = 0; i < segments.length; ++i) {
|
727 |
|
|
check += segments[i].count;
|
728 |
|
|
if (mc[i] != segments[i].modCount) {
|
729 |
|
|
check = -1; // force retry
|
730 |
|
|
break;
|
731 |
|
|
}
|
732 |
|
|
}
|
733 |
|
|
}
|
734 |
|
|
if (check == sum)
|
735 |
|
|
break;
|
736 |
|
|
}
|
737 |
|
|
if (check != sum) { // Resort to locking all segments
|
738 |
|
|
sum = 0;
|
739 |
|
|
for (int i = 0; i < segments.length; ++i)
|
740 |
|
|
segments[i].lock();
|
741 |
|
|
for (int i = 0; i < segments.length; ++i)
|
742 |
|
|
sum += segments[i].count;
|
743 |
|
|
for (int i = 0; i < segments.length; ++i)
|
744 |
|
|
segments[i].unlock();
|
745 |
|
|
}
|
746 |
|
|
if (sum > Integer.MAX_VALUE)
|
747 |
|
|
return Integer.MAX_VALUE;
|
748 |
|
|
else
|
749 |
|
|
return (int)sum;
|
750 |
|
|
}
|
751 |
|
|
|
752 |
|
|
/**
|
753 |
|
|
* Returns the value to which the specified key is mapped,
|
754 |
|
|
* or {@code null} if this map contains no mapping for the key.
|
755 |
|
|
*
|
756 |
|
|
* <p>More formally, if this map contains a mapping from a key
|
757 |
|
|
* {@code k} to a value {@code v} such that {@code key.equals(k)},
|
758 |
|
|
* then this method returns {@code v}; otherwise it returns
|
759 |
|
|
* {@code null}. (There can be at most one such mapping.)
|
760 |
|
|
*
|
761 |
|
|
* @throws NullPointerException if the specified key is null
|
762 |
|
|
*/
|
763 |
|
|
public V get(Object key) {
|
764 |
|
|
int hash = hash(key.hashCode());
|
765 |
|
|
return segmentFor(hash).get(key, hash);
|
766 |
|
|
}
|
767 |
|
|
|
768 |
|
|
/**
|
769 |
|
|
* Tests if the specified object is a key in this table.
|
770 |
|
|
*
|
771 |
|
|
* @param key possible key
|
772 |
|
|
* @return <tt>true</tt> if and only if the specified object
|
773 |
|
|
* is a key in this table, as determined by the
|
774 |
|
|
* <tt>equals</tt> method; <tt>false</tt> otherwise.
|
775 |
|
|
* @throws NullPointerException if the specified key is null
|
776 |
|
|
*/
|
777 |
|
|
public boolean containsKey(Object key) {
|
778 |
|
|
int hash = hash(key.hashCode());
|
779 |
|
|
return segmentFor(hash).containsKey(key, hash);
|
780 |
|
|
}
|
781 |
|
|
|
782 |
|
|
/**
|
783 |
|
|
* Returns <tt>true</tt> if this map maps one or more keys to the
|
784 |
|
|
* specified value. Note: This method requires a full internal
|
785 |
|
|
* traversal of the hash table, and so is much slower than
|
786 |
|
|
* method <tt>containsKey</tt>.
|
787 |
|
|
*
|
788 |
|
|
* @param value value whose presence in this map is to be tested
|
789 |
|
|
* @return <tt>true</tt> if this map maps one or more keys to the
|
790 |
|
|
* specified value
|
791 |
|
|
* @throws NullPointerException if the specified value is null
|
792 |
|
|
*/
|
793 |
|
|
public boolean containsValue(Object value) {
|
794 |
|
|
if (value == null)
|
795 |
|
|
throw new NullPointerException();
|
796 |
|
|
|
797 |
|
|
// See explanation of modCount use above
|
798 |
|
|
|
799 |
|
|
final Segment<K,V>[] segments = this.segments;
|
800 |
|
|
int[] mc = new int[segments.length];
|
801 |
|
|
|
802 |
|
|
// Try a few times without locking
|
803 |
|
|
for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) {
|
804 |
|
|
int sum = 0;
|
805 |
|
|
int mcsum = 0;
|
806 |
|
|
for (int i = 0; i < segments.length; ++i) {
|
807 |
|
|
int c = segments[i].count;
|
808 |
|
|
mcsum += mc[i] = segments[i].modCount;
|
809 |
|
|
if (segments[i].containsValue(value))
|
810 |
|
|
return true;
|
811 |
|
|
}
|
812 |
|
|
boolean cleanSweep = true;
|
813 |
|
|
if (mcsum != 0) {
|
814 |
|
|
for (int i = 0; i < segments.length; ++i) {
|
815 |
|
|
int c = segments[i].count;
|
816 |
|
|
if (mc[i] != segments[i].modCount) {
|
817 |
|
|
cleanSweep = false;
|
818 |
|
|
break;
|
819 |
|
|
}
|
820 |
|
|
}
|
821 |
|
|
}
|
822 |
|
|
if (cleanSweep)
|
823 |
|
|
return false;
|
824 |
|
|
}
|
825 |
|
|
// Resort to locking all segments
|
826 |
|
|
for (int i = 0; i < segments.length; ++i)
|
827 |
|
|
segments[i].lock();
|
828 |
|
|
boolean found = false;
|
829 |
|
|
try {
|
830 |
|
|
for (int i = 0; i < segments.length; ++i) {
|
831 |
|
|
if (segments[i].containsValue(value)) {
|
832 |
|
|
found = true;
|
833 |
|
|
break;
|
834 |
|
|
}
|
835 |
|
|
}
|
836 |
|
|
} finally {
|
837 |
|
|
for (int i = 0; i < segments.length; ++i)
|
838 |
|
|
segments[i].unlock();
|
839 |
|
|
}
|
840 |
|
|
return found;
|
841 |
|
|
}
|
842 |
|
|
|
843 |
|
|
/**
|
844 |
|
|
* Legacy method testing if some key maps into the specified value
|
845 |
|
|
* in this table. This method is identical in functionality to
|
846 |
|
|
* {@link #containsValue}, and exists solely to ensure
|
847 |
|
|
* full compatibility with class {@link java.util.Hashtable},
|
848 |
|
|
* which supported this method prior to introduction of the
|
849 |
|
|
* Java Collections framework.
|
850 |
|
|
|
851 |
|
|
* @param value a value to search for
|
852 |
|
|
* @return <tt>true</tt> if and only if some key maps to the
|
853 |
|
|
* <tt>value</tt> argument in this table as
|
854 |
|
|
* determined by the <tt>equals</tt> method;
|
855 |
|
|
* <tt>false</tt> otherwise
|
856 |
|
|
* @throws NullPointerException if the specified value is null
|
857 |
|
|
*/
|
858 |
|
|
public boolean contains(Object value) {
|
859 |
|
|
return containsValue(value);
|
860 |
|
|
}
|
861 |
|
|
|
862 |
|
|
/**
|
863 |
|
|
* Maps the specified key to the specified value in this table.
|
864 |
|
|
* Neither the key nor the value can be null.
|
865 |
|
|
*
|
866 |
|
|
* <p> The value can be retrieved by calling the <tt>get</tt> method
|
867 |
|
|
* with a key that is equal to the original key.
|
868 |
|
|
*
|
869 |
|
|
* @param key key with which the specified value is to be associated
|
870 |
|
|
* @param value value to be associated with the specified key
|
871 |
|
|
* @return the previous value associated with <tt>key</tt>, or
|
872 |
|
|
* <tt>null</tt> if there was no mapping for <tt>key</tt>
|
873 |
|
|
* @throws NullPointerException if the specified key or value is null
|
874 |
|
|
*/
|
875 |
|
|
public V put(K key, V value) {
|
876 |
|
|
if (value == null)
|
877 |
|
|
throw new NullPointerException();
|
878 |
|
|
int hash = hash(key.hashCode());
|
879 |
|
|
return segmentFor(hash).put(key, hash, value, false);
|
880 |
|
|
}
|
881 |
|
|
|
882 |
|
|
/**
|
883 |
|
|
* {@inheritDoc}
|
884 |
|
|
*
|
885 |
|
|
* @return the previous value associated with the specified key,
|
886 |
|
|
* or <tt>null</tt> if there was no mapping for the key
|
887 |
|
|
* @throws NullPointerException if the specified key or value is null
|
888 |
|
|
*/
|
889 |
|
|
public V putIfAbsent(K key, V value) {
|
890 |
|
|
if (value == null)
|
891 |
|
|
throw new NullPointerException();
|
892 |
|
|
int hash = hash(key.hashCode());
|
893 |
|
|
return segmentFor(hash).put(key, hash, value, true);
|
894 |
|
|
}
|
895 |
|
|
|
896 |
|
|
/**
|
897 |
|
|
* Copies all of the mappings from the specified map to this one.
|
898 |
|
|
* These mappings replace any mappings that this map had for any of the
|
899 |
|
|
* keys currently in the specified map.
|
900 |
|
|
*
|
901 |
|
|
* @param m mappings to be stored in this map
|
902 |
|
|
*/
|
903 |
|
|
public void putAll(Map<? extends K, ? extends V> m) {
|
904 |
|
|
for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
|
905 |
|
|
put(e.getKey(), e.getValue());
|
906 |
|
|
}
|
907 |
|
|
|
908 |
|
|
/**
|
909 |
|
|
* Removes the key (and its corresponding value) from this map.
|
910 |
|
|
* This method does nothing if the key is not in the map.
|
911 |
|
|
*
|
912 |
|
|
* @param key the key that needs to be removed
|
913 |
|
|
* @return the previous value associated with <tt>key</tt>, or
|
914 |
|
|
* <tt>null</tt> if there was no mapping for <tt>key</tt>
|
915 |
|
|
* @throws NullPointerException if the specified key is null
|
916 |
|
|
*/
|
917 |
|
|
public V remove(Object key) {
|
918 |
|
|
int hash = hash(key.hashCode());
|
919 |
|
|
return segmentFor(hash).remove(key, hash, null);
|
920 |
|
|
}
|
921 |
|
|
|
922 |
|
|
/**
|
923 |
|
|
* {@inheritDoc}
|
924 |
|
|
*
|
925 |
|
|
* @throws NullPointerException if the specified key is null
|
926 |
|
|
*/
|
927 |
|
|
public boolean remove(Object key, Object value) {
|
928 |
|
|
int hash = hash(key.hashCode());
|
929 |
|
|
if (value == null)
|
930 |
|
|
return false;
|
931 |
|
|
return segmentFor(hash).remove(key, hash, value) != null;
|
932 |
|
|
}
|
933 |
|
|
|
934 |
|
|
/**
|
935 |
|
|
* {@inheritDoc}
|
936 |
|
|
*
|
937 |
|
|
* @throws NullPointerException if any of the arguments are null
|
938 |
|
|
*/
|
939 |
|
|
public boolean replace(K key, V oldValue, V newValue) {
|
940 |
|
|
if (oldValue == null || newValue == null)
|
941 |
|
|
throw new NullPointerException();
|
942 |
|
|
int hash = hash(key.hashCode());
|
943 |
|
|
return segmentFor(hash).replace(key, hash, oldValue, newValue);
|
944 |
|
|
}
|
945 |
|
|
|
946 |
|
|
/**
|
947 |
|
|
* {@inheritDoc}
|
948 |
|
|
*
|
949 |
|
|
* @return the previous value associated with the specified key,
|
950 |
|
|
* or <tt>null</tt> if there was no mapping for the key
|
951 |
|
|
* @throws NullPointerException if the specified key or value is null
|
952 |
|
|
*/
|
953 |
|
|
public V replace(K key, V value) {
|
954 |
|
|
if (value == null)
|
955 |
|
|
throw new NullPointerException();
|
956 |
|
|
int hash = hash(key.hashCode());
|
957 |
|
|
return segmentFor(hash).replace(key, hash, value);
|
958 |
|
|
}
|
959 |
|
|
|
960 |
|
|
/**
|
961 |
|
|
* Removes all of the mappings from this map.
|
962 |
|
|
*/
|
963 |
|
|
public void clear() {
|
964 |
|
|
for (int i = 0; i < segments.length; ++i)
|
965 |
|
|
segments[i].clear();
|
966 |
|
|
}
|
967 |
|
|
|
968 |
|
|
/**
|
969 |
|
|
* Returns a {@link Set} view of the keys contained in this map.
|
970 |
|
|
* The set is backed by the map, so changes to the map are
|
971 |
|
|
* reflected in the set, and vice-versa. The set supports element
|
972 |
|
|
* removal, which removes the corresponding mapping from this map,
|
973 |
|
|
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
|
974 |
|
|
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
|
975 |
|
|
* operations. It does not support the <tt>add</tt> or
|
976 |
|
|
* <tt>addAll</tt> operations.
|
977 |
|
|
*
|
978 |
|
|
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
|
979 |
|
|
* that will never throw {@link ConcurrentModificationException},
|
980 |
|
|
* and guarantees to traverse elements as they existed upon
|
981 |
|
|
* construction of the iterator, and may (but is not guaranteed to)
|
982 |
|
|
* reflect any modifications subsequent to construction.
|
983 |
|
|
*/
|
984 |
|
|
public Set<K> keySet() {
|
985 |
|
|
Set<K> ks = keySet;
|
986 |
|
|
return (ks != null) ? ks : (keySet = new KeySet());
|
987 |
|
|
}
|
988 |
|
|
|
989 |
|
|
/**
|
990 |
|
|
* Returns a {@link Collection} view of the values contained in this map.
|
991 |
|
|
* The collection is backed by the map, so changes to the map are
|
992 |
|
|
* reflected in the collection, and vice-versa. The collection
|
993 |
|
|
* supports element removal, which removes the corresponding
|
994 |
|
|
* mapping from this map, via the <tt>Iterator.remove</tt>,
|
995 |
|
|
* <tt>Collection.remove</tt>, <tt>removeAll</tt>,
|
996 |
|
|
* <tt>retainAll</tt>, and <tt>clear</tt> operations. It does not
|
997 |
|
|
* support the <tt>add</tt> or <tt>addAll</tt> operations.
|
998 |
|
|
*
|
999 |
|
|
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
|
1000 |
|
|
* that will never throw {@link ConcurrentModificationException},
|
1001 |
|
|
* and guarantees to traverse elements as they existed upon
|
1002 |
|
|
* construction of the iterator, and may (but is not guaranteed to)
|
1003 |
|
|
* reflect any modifications subsequent to construction.
|
1004 |
|
|
*/
|
1005 |
|
|
public Collection<V> values() {
|
1006 |
|
|
Collection<V> vs = values;
|
1007 |
|
|
return (vs != null) ? vs : (values = new Values());
|
1008 |
|
|
}
|
1009 |
|
|
|
1010 |
|
|
/**
|
1011 |
|
|
* Returns a {@link Set} view of the mappings contained in this map.
|
1012 |
|
|
* The set is backed by the map, so changes to the map are
|
1013 |
|
|
* reflected in the set, and vice-versa. The set supports element
|
1014 |
|
|
* removal, which removes the corresponding mapping from the map,
|
1015 |
|
|
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
|
1016 |
|
|
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
|
1017 |
|
|
* operations. It does not support the <tt>add</tt> or
|
1018 |
|
|
* <tt>addAll</tt> operations.
|
1019 |
|
|
*
|
1020 |
|
|
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
|
1021 |
|
|
* that will never throw {@link ConcurrentModificationException},
|
1022 |
|
|
* and guarantees to traverse elements as they existed upon
|
1023 |
|
|
* construction of the iterator, and may (but is not guaranteed to)
|
1024 |
|
|
* reflect any modifications subsequent to construction.
|
1025 |
|
|
*/
|
1026 |
|
|
public Set<Map.Entry<K,V>> entrySet() {
|
1027 |
|
|
Set<Map.Entry<K,V>> es = entrySet;
|
1028 |
|
|
return (es != null) ? es : (entrySet = new EntrySet());
|
1029 |
|
|
}
|
1030 |
|
|
|
1031 |
|
|
/**
|
1032 |
|
|
* Returns an enumeration of the keys in this table.
|
1033 |
|
|
*
|
1034 |
|
|
* @return an enumeration of the keys in this table
|
1035 |
|
|
* @see #keySet
|
1036 |
|
|
*/
|
1037 |
|
|
public Enumeration<K> keys() {
|
1038 |
|
|
return new KeyIterator();
|
1039 |
|
|
}
|
1040 |
|
|
|
1041 |
|
|
/**
|
1042 |
|
|
* Returns an enumeration of the values in this table.
|
1043 |
|
|
*
|
1044 |
|
|
* @return an enumeration of the values in this table
|
1045 |
|
|
* @see #values
|
1046 |
|
|
*/
|
1047 |
|
|
public Enumeration<V> elements() {
|
1048 |
|
|
return new ValueIterator();
|
1049 |
|
|
}
|
1050 |
|
|
|
1051 |
|
|
/* ---------------- Iterator Support -------------- */
|
1052 |
|
|
|
1053 |
|
|
abstract class HashIterator {
|
1054 |
|
|
int nextSegmentIndex;
|
1055 |
|
|
int nextTableIndex;
|
1056 |
|
|
HashEntry<K,V>[] currentTable;
|
1057 |
|
|
HashEntry<K, V> nextEntry;
|
1058 |
|
|
HashEntry<K, V> lastReturned;
|
1059 |
|
|
|
1060 |
|
|
HashIterator() {
|
1061 |
|
|
nextSegmentIndex = segments.length - 1;
|
1062 |
|
|
nextTableIndex = -1;
|
1063 |
|
|
advance();
|
1064 |
|
|
}
|
1065 |
|
|
|
1066 |
|
|
public boolean hasMoreElements() { return hasNext(); }
|
1067 |
|
|
|
1068 |
|
|
final void advance() {
|
1069 |
|
|
if (nextEntry != null && (nextEntry = nextEntry.next) != null)
|
1070 |
|
|
return;
|
1071 |
|
|
|
1072 |
|
|
while (nextTableIndex >= 0) {
|
1073 |
|
|
if ( (nextEntry = currentTable[nextTableIndex--]) != null)
|
1074 |
|
|
return;
|
1075 |
|
|
}
|
1076 |
|
|
|
1077 |
|
|
while (nextSegmentIndex >= 0) {
|
1078 |
|
|
Segment<K,V> seg = segments[nextSegmentIndex--];
|
1079 |
|
|
if (seg.count != 0) {
|
1080 |
|
|
currentTable = seg.table;
|
1081 |
|
|
for (int j = currentTable.length - 1; j >= 0; --j) {
|
1082 |
|
|
if ( (nextEntry = currentTable[j]) != null) {
|
1083 |
|
|
nextTableIndex = j - 1;
|
1084 |
|
|
return;
|
1085 |
|
|
}
|
1086 |
|
|
}
|
1087 |
|
|
}
|
1088 |
|
|
}
|
1089 |
|
|
}
|
1090 |
|
|
|
1091 |
|
|
public boolean hasNext() { return nextEntry != null; }
|
1092 |
|
|
|
1093 |
|
|
HashEntry<K,V> nextEntry() {
|
1094 |
|
|
if (nextEntry == null)
|
1095 |
|
|
throw new NoSuchElementException();
|
1096 |
|
|
lastReturned = nextEntry;
|
1097 |
|
|
advance();
|
1098 |
|
|
return lastReturned;
|
1099 |
|
|
}
|
1100 |
|
|
|
1101 |
|
|
public void remove() {
|
1102 |
|
|
if (lastReturned == null)
|
1103 |
|
|
throw new IllegalStateException();
|
1104 |
|
|
ConcurrentHashMap.this.remove(lastReturned.key);
|
1105 |
|
|
lastReturned = null;
|
1106 |
|
|
}
|
1107 |
|
|
}
|
1108 |
|
|
|
1109 |
|
|
final class KeyIterator
|
1110 |
|
|
extends HashIterator
|
1111 |
|
|
implements Iterator<K>, Enumeration<K>
|
1112 |
|
|
{
|
1113 |
|
|
public K next() { return super.nextEntry().key; }
|
1114 |
|
|
public K nextElement() { return super.nextEntry().key; }
|
1115 |
|
|
}
|
1116 |
|
|
|
1117 |
|
|
final class ValueIterator
|
1118 |
|
|
extends HashIterator
|
1119 |
|
|
implements Iterator<V>, Enumeration<V>
|
1120 |
|
|
{
|
1121 |
|
|
public V next() { return super.nextEntry().value; }
|
1122 |
|
|
public V nextElement() { return super.nextEntry().value; }
|
1123 |
|
|
}
|
1124 |
|
|
|
1125 |
|
|
/**
|
1126 |
|
|
* Custom Entry class used by EntryIterator.next(), that relays
|
1127 |
|
|
* setValue changes to the underlying map.
|
1128 |
|
|
*/
|
1129 |
|
|
final class WriteThroughEntry
|
1130 |
|
|
extends AbstractMap.SimpleEntry<K,V>
|
1131 |
|
|
{
|
1132 |
|
|
WriteThroughEntry(K k, V v) {
|
1133 |
|
|
super(k,v);
|
1134 |
|
|
}
|
1135 |
|
|
|
1136 |
|
|
/**
|
1137 |
|
|
* Set our entry's value and write through to the map. The
|
1138 |
|
|
* value to return is somewhat arbitrary here. Since a
|
1139 |
|
|
* WriteThroughEntry does not necessarily track asynchronous
|
1140 |
|
|
* changes, the most recent "previous" value could be
|
1141 |
|
|
* different from what we return (or could even have been
|
1142 |
|
|
* removed in which case the put will re-establish). We do not
|
1143 |
|
|
* and cannot guarantee more.
|
1144 |
|
|
*/
|
1145 |
|
|
public V setValue(V value) {
|
1146 |
|
|
if (value == null) throw new NullPointerException();
|
1147 |
|
|
V v = super.setValue(value);
|
1148 |
|
|
ConcurrentHashMap.this.put(getKey(), value);
|
1149 |
|
|
return v;
|
1150 |
|
|
}
|
1151 |
|
|
}
|
1152 |
|
|
|
1153 |
|
|
final class EntryIterator
|
1154 |
|
|
extends HashIterator
|
1155 |
|
|
implements Iterator<Entry<K,V>>
|
1156 |
|
|
{
|
1157 |
|
|
public Map.Entry<K,V> next() {
|
1158 |
|
|
HashEntry<K,V> e = super.nextEntry();
|
1159 |
|
|
return new WriteThroughEntry(e.key, e.value);
|
1160 |
|
|
}
|
1161 |
|
|
}
|
1162 |
|
|
|
1163 |
|
|
final class KeySet extends AbstractSet<K> {
|
1164 |
|
|
public Iterator<K> iterator() {
|
1165 |
|
|
return new KeyIterator();
|
1166 |
|
|
}
|
1167 |
|
|
public int size() {
|
1168 |
|
|
return ConcurrentHashMap.this.size();
|
1169 |
|
|
}
|
1170 |
|
|
public boolean contains(Object o) {
|
1171 |
|
|
return ConcurrentHashMap.this.containsKey(o);
|
1172 |
|
|
}
|
1173 |
|
|
public boolean remove(Object o) {
|
1174 |
|
|
return ConcurrentHashMap.this.remove(o) != null;
|
1175 |
|
|
}
|
1176 |
|
|
public void clear() {
|
1177 |
|
|
ConcurrentHashMap.this.clear();
|
1178 |
|
|
}
|
1179 |
|
|
}
|
1180 |
|
|
|
1181 |
|
|
final class Values extends AbstractCollection<V> {
|
1182 |
|
|
public Iterator<V> iterator() {
|
1183 |
|
|
return new ValueIterator();
|
1184 |
|
|
}
|
1185 |
|
|
public int size() {
|
1186 |
|
|
return ConcurrentHashMap.this.size();
|
1187 |
|
|
}
|
1188 |
|
|
public boolean contains(Object o) {
|
1189 |
|
|
return ConcurrentHashMap.this.containsValue(o);
|
1190 |
|
|
}
|
1191 |
|
|
public void clear() {
|
1192 |
|
|
ConcurrentHashMap.this.clear();
|
1193 |
|
|
}
|
1194 |
|
|
}
|
1195 |
|
|
|
1196 |
|
|
final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
|
1197 |
|
|
public Iterator<Map.Entry<K,V>> iterator() {
|
1198 |
|
|
return new EntryIterator();
|
1199 |
|
|
}
|
1200 |
|
|
public boolean contains(Object o) {
|
1201 |
|
|
if (!(o instanceof Map.Entry))
|
1202 |
|
|
return false;
|
1203 |
|
|
Map.Entry<?,?> e = (Map.Entry<?,?>)o;
|
1204 |
|
|
V v = ConcurrentHashMap.this.get(e.getKey());
|
1205 |
|
|
return v != null && v.equals(e.getValue());
|
1206 |
|
|
}
|
1207 |
|
|
public boolean remove(Object o) {
|
1208 |
|
|
if (!(o instanceof Map.Entry))
|
1209 |
|
|
return false;
|
1210 |
|
|
Map.Entry<?,?> e = (Map.Entry<?,?>)o;
|
1211 |
|
|
return ConcurrentHashMap.this.remove(e.getKey(), e.getValue());
|
1212 |
|
|
}
|
1213 |
|
|
public int size() {
|
1214 |
|
|
return ConcurrentHashMap.this.size();
|
1215 |
|
|
}
|
1216 |
|
|
public void clear() {
|
1217 |
|
|
ConcurrentHashMap.this.clear();
|
1218 |
|
|
}
|
1219 |
|
|
}
|
1220 |
|
|
|
1221 |
|
|
/* ---------------- Serialization Support -------------- */
|
1222 |
|
|
|
1223 |
|
|
/**
|
1224 |
|
|
* Save the state of the <tt>ConcurrentHashMap</tt> instance to a
|
1225 |
|
|
* stream (i.e., serialize it).
|
1226 |
|
|
* @param s the stream
|
1227 |
|
|
* @serialData
|
1228 |
|
|
* the key (Object) and value (Object)
|
1229 |
|
|
* for each key-value mapping, followed by a null pair.
|
1230 |
|
|
* The key-value mappings are emitted in no particular order.
|
1231 |
|
|
*/
|
1232 |
|
|
private void writeObject(java.io.ObjectOutputStream s) throws IOException {
|
1233 |
|
|
s.defaultWriteObject();
|
1234 |
|
|
|
1235 |
|
|
for (int k = 0; k < segments.length; ++k) {
|
1236 |
|
|
Segment<K,V> seg = segments[k];
|
1237 |
|
|
seg.lock();
|
1238 |
|
|
try {
|
1239 |
|
|
HashEntry<K,V>[] tab = seg.table;
|
1240 |
|
|
for (int i = 0; i < tab.length; ++i) {
|
1241 |
|
|
for (HashEntry<K,V> e = tab[i]; e != null; e = e.next) {
|
1242 |
|
|
s.writeObject(e.key);
|
1243 |
|
|
s.writeObject(e.value);
|
1244 |
|
|
}
|
1245 |
|
|
}
|
1246 |
|
|
} finally {
|
1247 |
|
|
seg.unlock();
|
1248 |
|
|
}
|
1249 |
|
|
}
|
1250 |
|
|
s.writeObject(null);
|
1251 |
|
|
s.writeObject(null);
|
1252 |
|
|
}
|
1253 |
|
|
|
1254 |
|
|
/**
|
1255 |
|
|
* Reconstitute the <tt>ConcurrentHashMap</tt> instance from a
|
1256 |
|
|
* stream (i.e., deserialize it).
|
1257 |
|
|
* @param s the stream
|
1258 |
|
|
*/
|
1259 |
|
|
private void readObject(java.io.ObjectInputStream s)
|
1260 |
|
|
throws IOException, ClassNotFoundException {
|
1261 |
|
|
s.defaultReadObject();
|
1262 |
|
|
|
1263 |
|
|
// Initialize each segment to be minimally sized, and let grow.
|
1264 |
|
|
for (int i = 0; i < segments.length; ++i) {
|
1265 |
|
|
segments[i].setTable(new HashEntry[1]);
|
1266 |
|
|
}
|
1267 |
|
|
|
1268 |
|
|
// Read the keys and values, and put the mappings in the table
|
1269 |
|
|
for (;;) {
|
1270 |
|
|
K key = (K) s.readObject();
|
1271 |
|
|
V value = (V) s.readObject();
|
1272 |
|
|
if (key == null)
|
1273 |
|
|
break;
|
1274 |
|
|
put(key, value);
|
1275 |
|
|
}
|
1276 |
|
|
}
|
1277 |
|
|
}
|