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/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Sun designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Sun in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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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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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 or upper bits.
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*/
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private static int hash(int h) {
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// Spread bits to regularize both segment and index locations,
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// using variant of single-word Wang/Jenkins hash.
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h += (h << 15) ^ 0xffffcd7d;
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h ^= (h >>> 10);
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h += (h << 3);
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h ^= (h >>> 6);
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h += (h << 2) + (h << 14);
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return h ^ (h >>> 16);
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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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325 |
}
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326 |
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327 |
/**
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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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330 |
*/
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void setTable(HashEntry<K,V>[] newTable) {
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332 |
threshold = (int)(newTable.length * loadFactor);
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table = newTable;
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}
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335 |
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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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342 |
}
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343 |
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344 |
/**
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* Reads value field of an entry under lock. Called if value
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346 |
* field ever appears to be null. This is possible only if a
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347 |
* compiler happens to reorder a HashEntry initialization with
|
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348 |
* its table assignment, which is legal under memory model
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349 |
* but is not known to ever occur.
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350 |
*/
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351 |
V readValueUnderLock(HashEntry<K,V> e) {
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352 |
lock();
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353 |
try {
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354 |
return e.value;
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355 |
} finally {
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356 |
unlock();
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357 |
}
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358 |
}
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359 |
|
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360 |
/* Specialized implementations of map methods */
|
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361 |
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362 |
V get(Object key, int hash) {
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363 |
if (count != 0) { // read-volatile
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364 |
HashEntry<K,V> e = getFirst(hash);
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365 |
while (e != null) {
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366 |
if (e.hash == hash && key.equals(e.key)) {
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367 |
V v = e.value;
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368 |
if (v != null)
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369 |
return v;
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370 |
return readValueUnderLock(e); // recheck
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371 |
}
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372 |
e = e.next;
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373 |
}
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374 |
}
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375 |
return null;
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376 |
}
|
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377 |
|
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378 |
boolean containsKey(Object key, int hash) {
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379 |
if (count != 0) { // read-volatile
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380 |
HashEntry<K,V> e = getFirst(hash);
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381 |
while (e != null) {
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382 |
if (e.hash == hash && key.equals(e.key))
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383 |
return true;
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384 |
e = e.next;
|
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385 |
}
|
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386 |
}
|
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387 |
return false;
|
|
388 |
}
|
|
389 |
|
|
390 |
boolean containsValue(Object value) {
|
|
391 |
if (count != 0) { // read-volatile
|
|
392 |
HashEntry<K,V>[] tab = table;
|
|
393 |
int len = tab.length;
|
|
394 |
for (int i = 0 ; i < len; i++) {
|
|
395 |
for (HashEntry<K,V> e = tab[i]; e != null; e = e.next) {
|
|
396 |
V v = e.value;
|
|
397 |
if (v == null) // recheck
|
|
398 |
v = readValueUnderLock(e);
|
|
399 |
if (value.equals(v))
|
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400 |
return true;
|
|
401 |
}
|
|
402 |
}
|
|
403 |
}
|
|
404 |
return false;
|
|
405 |
}
|
|
406 |
|
|
407 |
boolean replace(K key, int hash, V oldValue, V newValue) {
|
|
408 |
lock();
|
|
409 |
try {
|
|
410 |
HashEntry<K,V> e = getFirst(hash);
|
|
411 |
while (e != null && (e.hash != hash || !key.equals(e.key)))
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412 |
e = e.next;
|
|
413 |
|
|
414 |
boolean replaced = false;
|
|
415 |
if (e != null && oldValue.equals(e.value)) {
|
|
416 |
replaced = true;
|
|
417 |
e.value = newValue;
|
|
418 |
}
|
|
419 |
return replaced;
|
|
420 |
} finally {
|
|
421 |
unlock();
|
|
422 |
}
|
|
423 |
}
|
|
424 |
|
|
425 |
V replace(K key, int hash, V newValue) {
|
|
426 |
lock();
|
|
427 |
try {
|
|
428 |
HashEntry<K,V> e = getFirst(hash);
|
|
429 |
while (e != null && (e.hash != hash || !key.equals(e.key)))
|
|
430 |
e = e.next;
|
|
431 |
|
|
432 |
V oldValue = null;
|
|
433 |
if (e != null) {
|
|
434 |
oldValue = e.value;
|
|
435 |
e.value = newValue;
|
|
436 |
}
|
|
437 |
return oldValue;
|
|
438 |
} finally {
|
|
439 |
unlock();
|
|
440 |
}
|
|
441 |
}
|
|
442 |
|
|
443 |
|
|
444 |
V put(K key, int hash, V value, boolean onlyIfAbsent) {
|
|
445 |
lock();
|
|
446 |
try {
|
|
447 |
int c = count;
|
|
448 |
if (c++ > threshold) // ensure capacity
|
|
449 |
rehash();
|
|
450 |
HashEntry<K,V>[] tab = table;
|
|
451 |
int index = hash & (tab.length - 1);
|
|
452 |
HashEntry<K,V> first = tab[index];
|
|
453 |
HashEntry<K,V> e = first;
|
|
454 |
while (e != null && (e.hash != hash || !key.equals(e.key)))
|
|
455 |
e = e.next;
|
|
456 |
|
|
457 |
V oldValue;
|
|
458 |
if (e != null) {
|
|
459 |
oldValue = e.value;
|
|
460 |
if (!onlyIfAbsent)
|
|
461 |
e.value = value;
|
|
462 |
}
|
|
463 |
else {
|
|
464 |
oldValue = null;
|
|
465 |
++modCount;
|
|
466 |
tab[index] = new HashEntry<K,V>(key, hash, first, value);
|
|
467 |
count = c; // write-volatile
|
|
468 |
}
|
|
469 |
return oldValue;
|
|
470 |
} finally {
|
|
471 |
unlock();
|
|
472 |
}
|
|
473 |
}
|
|
474 |
|
|
475 |
void rehash() {
|
|
476 |
HashEntry<K,V>[] oldTable = table;
|
|
477 |
int oldCapacity = oldTable.length;
|
|
478 |
if (oldCapacity >= MAXIMUM_CAPACITY)
|
|
479 |
return;
|
|
480 |
|
|
481 |
/*
|
|
482 |
* Reclassify nodes in each list to new Map. Because we are
|
|
483 |
* using power-of-two expansion, the elements from each bin
|
|
484 |
* must either stay at same index, or move with a power of two
|
|
485 |
* offset. We eliminate unnecessary node creation by catching
|
|
486 |
* cases where old nodes can be reused because their next
|
|
487 |
* fields won't change. Statistically, at the default
|
|
488 |
* threshold, only about one-sixth of them need cloning when
|
|
489 |
* a table doubles. The nodes they replace will be garbage
|
|
490 |
* collectable as soon as they are no longer referenced by any
|
|
491 |
* reader thread that may be in the midst of traversing table
|
|
492 |
* right now.
|
|
493 |
*/
|
|
494 |
|
|
495 |
HashEntry<K,V>[] newTable = HashEntry.newArray(oldCapacity<<1);
|
|
496 |
threshold = (int)(newTable.length * loadFactor);
|
|
497 |
int sizeMask = newTable.length - 1;
|
|
498 |
for (int i = 0; i < oldCapacity ; i++) {
|
|
499 |
// We need to guarantee that any existing reads of old Map can
|
|
500 |
// proceed. So we cannot yet null out each bin.
|
|
501 |
HashEntry<K,V> e = oldTable[i];
|
|
502 |
|
|
503 |
if (e != null) {
|
|
504 |
HashEntry<K,V> next = e.next;
|
|
505 |
int idx = e.hash & sizeMask;
|
|
506 |
|
|
507 |
// Single node on list
|
|
508 |
if (next == null)
|
|
509 |
newTable[idx] = e;
|
|
510 |
|
|
511 |
else {
|
|
512 |
// Reuse trailing consecutive sequence at same slot
|
|
513 |
HashEntry<K,V> lastRun = e;
|
|
514 |
int lastIdx = idx;
|
|
515 |
for (HashEntry<K,V> last = next;
|
|
516 |
last != null;
|
|
517 |
last = last.next) {
|
|
518 |
int k = last.hash & sizeMask;
|
|
519 |
if (k != lastIdx) {
|
|
520 |
lastIdx = k;
|
|
521 |
lastRun = last;
|
|
522 |
}
|
|
523 |
}
|
|
524 |
newTable[lastIdx] = lastRun;
|
|
525 |
|
|
526 |
// Clone all remaining nodes
|
|
527 |
for (HashEntry<K,V> p = e; p != lastRun; p = p.next) {
|
|
528 |
int k = p.hash & sizeMask;
|
|
529 |
HashEntry<K,V> n = newTable[k];
|
|
530 |
newTable[k] = new HashEntry<K,V>(p.key, p.hash,
|
|
531 |
n, p.value);
|
|
532 |
}
|
|
533 |
}
|
|
534 |
}
|
|
535 |
}
|
|
536 |
table = newTable;
|
|
537 |
}
|
|
538 |
|
|
539 |
/**
|
|
540 |
* Remove; match on key only if value null, else match both.
|
|
541 |
*/
|
|
542 |
V remove(Object key, int hash, Object value) {
|
|
543 |
lock();
|
|
544 |
try {
|
|
545 |
int c = count - 1;
|
|
546 |
HashEntry<K,V>[] tab = table;
|
|
547 |
int index = hash & (tab.length - 1);
|
|
548 |
HashEntry<K,V> first = tab[index];
|
|
549 |
HashEntry<K,V> e = first;
|
|
550 |
while (e != null && (e.hash != hash || !key.equals(e.key)))
|
|
551 |
e = e.next;
|
|
552 |
|
|
553 |
V oldValue = null;
|
|
554 |
if (e != null) {
|
|
555 |
V v = e.value;
|
|
556 |
if (value == null || value.equals(v)) {
|
|
557 |
oldValue = v;
|
|
558 |
// All entries following removed node can stay
|
|
559 |
// in list, but all preceding ones need to be
|
|
560 |
// cloned.
|
|
561 |
++modCount;
|
|
562 |
HashEntry<K,V> newFirst = e.next;
|
|
563 |
for (HashEntry<K,V> p = first; p != e; p = p.next)
|
|
564 |
newFirst = new HashEntry<K,V>(p.key, p.hash,
|
|
565 |
newFirst, p.value);
|
|
566 |
tab[index] = newFirst;
|
|
567 |
count = c; // write-volatile
|
|
568 |
}
|
|
569 |
}
|
|
570 |
return oldValue;
|
|
571 |
} finally {
|
|
572 |
unlock();
|
|
573 |
}
|
|
574 |
}
|
|
575 |
|
|
576 |
void clear() {
|
|
577 |
if (count != 0) {
|
|
578 |
lock();
|
|
579 |
try {
|
|
580 |
HashEntry<K,V>[] tab = table;
|
|
581 |
for (int i = 0; i < tab.length ; i++)
|
|
582 |
tab[i] = null;
|
|
583 |
++modCount;
|
|
584 |
count = 0; // write-volatile
|
|
585 |
} finally {
|
|
586 |
unlock();
|
|
587 |
}
|
|
588 |
}
|
|
589 |
}
|
|
590 |
}
|
|
591 |
|
|
592 |
|
|
593 |
|
|
594 |
/* ---------------- Public operations -------------- */
|
|
595 |
|
|
596 |
/**
|
|
597 |
* Creates a new, empty map with the specified initial
|
|
598 |
* capacity, load factor and concurrency level.
|
|
599 |
*
|
|
600 |
* @param initialCapacity the initial capacity. The implementation
|
|
601 |
* performs internal sizing to accommodate this many elements.
|
|
602 |
* @param loadFactor the load factor threshold, used to control resizing.
|
|
603 |
* Resizing may be performed when the average number of elements per
|
|
604 |
* bin exceeds this threshold.
|
|
605 |
* @param concurrencyLevel the estimated number of concurrently
|
|
606 |
* updating threads. The implementation performs internal sizing
|
|
607 |
* to try to accommodate this many threads.
|
|
608 |
* @throws IllegalArgumentException if the initial capacity is
|
|
609 |
* negative or the load factor or concurrencyLevel are
|
|
610 |
* nonpositive.
|
|
611 |
*/
|
|
612 |
public ConcurrentHashMap(int initialCapacity,
|
|
613 |
float loadFactor, int concurrencyLevel) {
|
|
614 |
if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0)
|
|
615 |
throw new IllegalArgumentException();
|
|
616 |
|
|
617 |
if (concurrencyLevel > MAX_SEGMENTS)
|
|
618 |
concurrencyLevel = MAX_SEGMENTS;
|
|
619 |
|
|
620 |
// Find power-of-two sizes best matching arguments
|
|
621 |
int sshift = 0;
|
|
622 |
int ssize = 1;
|
|
623 |
while (ssize < concurrencyLevel) {
|
|
624 |
++sshift;
|
|
625 |
ssize <<= 1;
|
|
626 |
}
|
|
627 |
segmentShift = 32 - sshift;
|
|
628 |
segmentMask = ssize - 1;
|
|
629 |
this.segments = Segment.newArray(ssize);
|
|
630 |
|
|
631 |
if (initialCapacity > MAXIMUM_CAPACITY)
|
|
632 |
initialCapacity = MAXIMUM_CAPACITY;
|
|
633 |
int c = initialCapacity / ssize;
|
|
634 |
if (c * ssize < initialCapacity)
|
|
635 |
++c;
|
|
636 |
int cap = 1;
|
|
637 |
while (cap < c)
|
|
638 |
cap <<= 1;
|
|
639 |
|
|
640 |
for (int i = 0; i < this.segments.length; ++i)
|
|
641 |
this.segments[i] = new Segment<K,V>(cap, loadFactor);
|
|
642 |
}
|
|
643 |
|
|
644 |
/**
|
|
645 |
* Creates a new, empty map with the specified initial capacity
|
|
646 |
* and load factor and with the default concurrencyLevel (16).
|
|
647 |
*
|
|
648 |
* @param initialCapacity The implementation performs internal
|
|
649 |
* sizing to accommodate this many elements.
|
|
650 |
* @param loadFactor the load factor threshold, used to control resizing.
|
|
651 |
* Resizing may be performed when the average number of elements per
|
|
652 |
* bin exceeds this threshold.
|
|
653 |
* @throws IllegalArgumentException if the initial capacity of
|
|
654 |
* elements is negative or the load factor is nonpositive
|
|
655 |
*
|
|
656 |
* @since 1.6
|
|
657 |
*/
|
|
658 |
public ConcurrentHashMap(int initialCapacity, float loadFactor) {
|
|
659 |
this(initialCapacity, loadFactor, DEFAULT_CONCURRENCY_LEVEL);
|
|
660 |
}
|
|
661 |
|
|
662 |
/**
|
|
663 |
* Creates a new, empty map with the specified initial capacity,
|
|
664 |
* and with default load factor (0.75) and concurrencyLevel (16).
|
|
665 |
*
|
|
666 |
* @param initialCapacity the initial capacity. The implementation
|
|
667 |
* performs internal sizing to accommodate this many elements.
|
|
668 |
* @throws IllegalArgumentException if the initial capacity of
|
|
669 |
* elements is negative.
|
|
670 |
*/
|
|
671 |
public ConcurrentHashMap(int initialCapacity) {
|
|
672 |
this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
|
|
673 |
}
|
|
674 |
|
|
675 |
/**
|
|
676 |
* Creates a new, empty map with a default initial capacity (16),
|
|
677 |
* load factor (0.75) and concurrencyLevel (16).
|
|
678 |
*/
|
|
679 |
public ConcurrentHashMap() {
|
|
680 |
this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
|
|
681 |
}
|
|
682 |
|
|
683 |
/**
|
|
684 |
* Creates a new map with the same mappings as the given map.
|
|
685 |
* The map is created with a capacity of 1.5 times the number
|
|
686 |
* of mappings in the given map or 16 (whichever is greater),
|
|
687 |
* and a default load factor (0.75) and concurrencyLevel (16).
|
|
688 |
*
|
|
689 |
* @param m the map
|
|
690 |
*/
|
|
691 |
public ConcurrentHashMap(Map<? extends K, ? extends V> m) {
|
|
692 |
this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
|
|
693 |
DEFAULT_INITIAL_CAPACITY),
|
|
694 |
DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
|
|
695 |
putAll(m);
|
|
696 |
}
|
|
697 |
|
|
698 |
/**
|
|
699 |
* Returns <tt>true</tt> if this map contains no key-value mappings.
|
|
700 |
*
|
|
701 |
* @return <tt>true</tt> if this map contains no key-value mappings
|
|
702 |
*/
|
|
703 |
public boolean isEmpty() {
|
|
704 |
final Segment<K,V>[] segments = this.segments;
|
|
705 |
/*
|
|
706 |
* We keep track of per-segment modCounts to avoid ABA
|
|
707 |
* problems in which an element in one segment was added and
|
|
708 |
* in another removed during traversal, in which case the
|
|
709 |
* table was never actually empty at any point. Note the
|
|
710 |
* similar use of modCounts in the size() and containsValue()
|
|
711 |
* methods, which are the only other methods also susceptible
|
|
712 |
* to ABA problems.
|
|
713 |
*/
|
|
714 |
int[] mc = new int[segments.length];
|
|
715 |
int mcsum = 0;
|
|
716 |
for (int i = 0; i < segments.length; ++i) {
|
|
717 |
if (segments[i].count != 0)
|
|
718 |
return false;
|
|
719 |
else
|
|
720 |
mcsum += mc[i] = segments[i].modCount;
|
|
721 |
}
|
|
722 |
// If mcsum happens to be zero, then we know we got a snapshot
|
|
723 |
// before any modifications at all were made. This is
|
|
724 |
// probably common enough to bother tracking.
|
|
725 |
if (mcsum != 0) {
|
|
726 |
for (int i = 0; i < segments.length; ++i) {
|
|
727 |
if (segments[i].count != 0 ||
|
|
728 |
mc[i] != segments[i].modCount)
|
|
729 |
return false;
|
|
730 |
}
|
|
731 |
}
|
|
732 |
return true;
|
|
733 |
}
|
|
734 |
|
|
735 |
/**
|
|
736 |
* Returns the number of key-value mappings in this map. If the
|
|
737 |
* map contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
|
|
738 |
* <tt>Integer.MAX_VALUE</tt>.
|
|
739 |
*
|
|
740 |
* @return the number of key-value mappings in this map
|
|
741 |
*/
|
|
742 |
public int size() {
|
|
743 |
final Segment<K,V>[] segments = this.segments;
|
|
744 |
long sum = 0;
|
|
745 |
long check = 0;
|
|
746 |
int[] mc = new int[segments.length];
|
|
747 |
// Try a few times to get accurate count. On failure due to
|
|
748 |
// continuous async changes in table, resort to locking.
|
|
749 |
for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) {
|
|
750 |
check = 0;
|
|
751 |
sum = 0;
|
|
752 |
int mcsum = 0;
|
|
753 |
for (int i = 0; i < segments.length; ++i) {
|
|
754 |
sum += segments[i].count;
|
|
755 |
mcsum += mc[i] = segments[i].modCount;
|
|
756 |
}
|
|
757 |
if (mcsum != 0) {
|
|
758 |
for (int i = 0; i < segments.length; ++i) {
|
|
759 |
check += segments[i].count;
|
|
760 |
if (mc[i] != segments[i].modCount) {
|
|
761 |
check = -1; // force retry
|
|
762 |
break;
|
|
763 |
}
|
|
764 |
}
|
|
765 |
}
|
|
766 |
if (check == sum)
|
|
767 |
break;
|
|
768 |
}
|
|
769 |
if (check != sum) { // Resort to locking all segments
|
|
770 |
sum = 0;
|
|
771 |
for (int i = 0; i < segments.length; ++i)
|
|
772 |
segments[i].lock();
|
|
773 |
for (int i = 0; i < segments.length; ++i)
|
|
774 |
sum += segments[i].count;
|
|
775 |
for (int i = 0; i < segments.length; ++i)
|
|
776 |
segments[i].unlock();
|
|
777 |
}
|
|
778 |
if (sum > Integer.MAX_VALUE)
|
|
779 |
return Integer.MAX_VALUE;
|
|
780 |
else
|
|
781 |
return (int)sum;
|
|
782 |
}
|
|
783 |
|
|
784 |
/**
|
|
785 |
* Returns the value to which the specified key is mapped,
|
|
786 |
* or {@code null} if this map contains no mapping for the key.
|
|
787 |
*
|
|
788 |
* <p>More formally, if this map contains a mapping from a key
|
|
789 |
* {@code k} to a value {@code v} such that {@code key.equals(k)},
|
|
790 |
* then this method returns {@code v}; otherwise it returns
|
|
791 |
* {@code null}. (There can be at most one such mapping.)
|
|
792 |
*
|
|
793 |
* @throws NullPointerException if the specified key is null
|
|
794 |
*/
|
|
795 |
public V get(Object key) {
|
|
796 |
int hash = hash(key.hashCode());
|
|
797 |
return segmentFor(hash).get(key, hash);
|
|
798 |
}
|
|
799 |
|
|
800 |
/**
|
|
801 |
* Tests if the specified object is a key in this table.
|
|
802 |
*
|
|
803 |
* @param key possible key
|
|
804 |
* @return <tt>true</tt> if and only if the specified object
|
|
805 |
* is a key in this table, as determined by the
|
|
806 |
* <tt>equals</tt> method; <tt>false</tt> otherwise.
|
|
807 |
* @throws NullPointerException if the specified key is null
|
|
808 |
*/
|
|
809 |
public boolean containsKey(Object key) {
|
|
810 |
int hash = hash(key.hashCode());
|
|
811 |
return segmentFor(hash).containsKey(key, hash);
|
|
812 |
}
|
|
813 |
|
|
814 |
/**
|
|
815 |
* Returns <tt>true</tt> if this map maps one or more keys to the
|
|
816 |
* specified value. Note: This method requires a full internal
|
|
817 |
* traversal of the hash table, and so is much slower than
|
|
818 |
* method <tt>containsKey</tt>.
|
|
819 |
*
|
|
820 |
* @param value value whose presence in this map is to be tested
|
|
821 |
* @return <tt>true</tt> if this map maps one or more keys to the
|
|
822 |
* specified value
|
|
823 |
* @throws NullPointerException if the specified value is null
|
|
824 |
*/
|
|
825 |
public boolean containsValue(Object value) {
|
|
826 |
if (value == null)
|
|
827 |
throw new NullPointerException();
|
|
828 |
|
|
829 |
// See explanation of modCount use above
|
|
830 |
|
|
831 |
final Segment<K,V>[] segments = this.segments;
|
|
832 |
int[] mc = new int[segments.length];
|
|
833 |
|
|
834 |
// Try a few times without locking
|
|
835 |
for (int k = 0; k < RETRIES_BEFORE_LOCK; ++k) {
|
|
836 |
int sum = 0;
|
|
837 |
int mcsum = 0;
|
|
838 |
for (int i = 0; i < segments.length; ++i) {
|
|
839 |
int c = segments[i].count;
|
|
840 |
mcsum += mc[i] = segments[i].modCount;
|
|
841 |
if (segments[i].containsValue(value))
|
|
842 |
return true;
|
|
843 |
}
|
|
844 |
boolean cleanSweep = true;
|
|
845 |
if (mcsum != 0) {
|
|
846 |
for (int i = 0; i < segments.length; ++i) {
|
|
847 |
int c = segments[i].count;
|
|
848 |
if (mc[i] != segments[i].modCount) {
|
|
849 |
cleanSweep = false;
|
|
850 |
break;
|
|
851 |
}
|
|
852 |
}
|
|
853 |
}
|
|
854 |
if (cleanSweep)
|
|
855 |
return false;
|
|
856 |
}
|
|
857 |
// Resort to locking all segments
|
|
858 |
for (int i = 0; i < segments.length; ++i)
|
|
859 |
segments[i].lock();
|
|
860 |
boolean found = false;
|
|
861 |
try {
|
|
862 |
for (int i = 0; i < segments.length; ++i) {
|
|
863 |
if (segments[i].containsValue(value)) {
|
|
864 |
found = true;
|
|
865 |
break;
|
|
866 |
}
|
|
867 |
}
|
|
868 |
} finally {
|
|
869 |
for (int i = 0; i < segments.length; ++i)
|
|
870 |
segments[i].unlock();
|
|
871 |
}
|
|
872 |
return found;
|
|
873 |
}
|
|
874 |
|
|
875 |
/**
|
|
876 |
* Legacy method testing if some key maps into the specified value
|
|
877 |
* in this table. This method is identical in functionality to
|
|
878 |
* {@link #containsValue}, and exists solely to ensure
|
|
879 |
* full compatibility with class {@link java.util.Hashtable},
|
|
880 |
* which supported this method prior to introduction of the
|
|
881 |
* Java Collections framework.
|
|
882 |
|
|
883 |
* @param value a value to search for
|
|
884 |
* @return <tt>true</tt> if and only if some key maps to the
|
|
885 |
* <tt>value</tt> argument in this table as
|
|
886 |
* determined by the <tt>equals</tt> method;
|
|
887 |
* <tt>false</tt> otherwise
|
|
888 |
* @throws NullPointerException if the specified value is null
|
|
889 |
*/
|
|
890 |
public boolean contains(Object value) {
|
|
891 |
return containsValue(value);
|
|
892 |
}
|
|
893 |
|
|
894 |
/**
|
|
895 |
* Maps the specified key to the specified value in this table.
|
|
896 |
* Neither the key nor the value can be null.
|
|
897 |
*
|
|
898 |
* <p> The value can be retrieved by calling the <tt>get</tt> method
|
|
899 |
* with a key that is equal to the original key.
|
|
900 |
*
|
|
901 |
* @param key key with which the specified value is to be associated
|
|
902 |
* @param value value to be associated with the specified key
|
|
903 |
* @return the previous value associated with <tt>key</tt>, or
|
|
904 |
* <tt>null</tt> if there was no mapping for <tt>key</tt>
|
|
905 |
* @throws NullPointerException if the specified key or value is null
|
|
906 |
*/
|
|
907 |
public V put(K key, V value) {
|
|
908 |
if (value == null)
|
|
909 |
throw new NullPointerException();
|
|
910 |
int hash = hash(key.hashCode());
|
|
911 |
return segmentFor(hash).put(key, hash, value, false);
|
|
912 |
}
|
|
913 |
|
|
914 |
/**
|
|
915 |
* {@inheritDoc}
|
|
916 |
*
|
|
917 |
* @return the previous value associated with the specified key,
|
|
918 |
* or <tt>null</tt> if there was no mapping for the key
|
|
919 |
* @throws NullPointerException if the specified key or value is null
|
|
920 |
*/
|
|
921 |
public V putIfAbsent(K key, V value) {
|
|
922 |
if (value == null)
|
|
923 |
throw new NullPointerException();
|
|
924 |
int hash = hash(key.hashCode());
|
|
925 |
return segmentFor(hash).put(key, hash, value, true);
|
|
926 |
}
|
|
927 |
|
|
928 |
/**
|
|
929 |
* Copies all of the mappings from the specified map to this one.
|
|
930 |
* These mappings replace any mappings that this map had for any of the
|
|
931 |
* keys currently in the specified map.
|
|
932 |
*
|
|
933 |
* @param m mappings to be stored in this map
|
|
934 |
*/
|
|
935 |
public void putAll(Map<? extends K, ? extends V> m) {
|
|
936 |
for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
|
|
937 |
put(e.getKey(), e.getValue());
|
|
938 |
}
|
|
939 |
|
|
940 |
/**
|
|
941 |
* Removes the key (and its corresponding value) from this map.
|
|
942 |
* This method does nothing if the key is not in the map.
|
|
943 |
*
|
|
944 |
* @param key the key that needs to be removed
|
|
945 |
* @return the previous value associated with <tt>key</tt>, or
|
|
946 |
* <tt>null</tt> if there was no mapping for <tt>key</tt>
|
|
947 |
* @throws NullPointerException if the specified key is null
|
|
948 |
*/
|
|
949 |
public V remove(Object key) {
|
|
950 |
int hash = hash(key.hashCode());
|
|
951 |
return segmentFor(hash).remove(key, hash, null);
|
|
952 |
}
|
|
953 |
|
|
954 |
/**
|
|
955 |
* {@inheritDoc}
|
|
956 |
*
|
|
957 |
* @throws NullPointerException if the specified key is null
|
|
958 |
*/
|
|
959 |
public boolean remove(Object key, Object value) {
|
|
960 |
int hash = hash(key.hashCode());
|
|
961 |
if (value == null)
|
|
962 |
return false;
|
|
963 |
return segmentFor(hash).remove(key, hash, value) != null;
|
|
964 |
}
|
|
965 |
|
|
966 |
/**
|
|
967 |
* {@inheritDoc}
|
|
968 |
*
|
|
969 |
* @throws NullPointerException if any of the arguments are null
|
|
970 |
*/
|
|
971 |
public boolean replace(K key, V oldValue, V newValue) {
|
|
972 |
if (oldValue == null || newValue == null)
|
|
973 |
throw new NullPointerException();
|
|
974 |
int hash = hash(key.hashCode());
|
|
975 |
return segmentFor(hash).replace(key, hash, oldValue, newValue);
|
|
976 |
}
|
|
977 |
|
|
978 |
/**
|
|
979 |
* {@inheritDoc}
|
|
980 |
*
|
|
981 |
* @return the previous value associated with the specified key,
|
|
982 |
* or <tt>null</tt> if there was no mapping for the key
|
|
983 |
* @throws NullPointerException if the specified key or value is null
|
|
984 |
*/
|
|
985 |
public V replace(K key, V value) {
|
|
986 |
if (value == null)
|
|
987 |
throw new NullPointerException();
|
|
988 |
int hash = hash(key.hashCode());
|
|
989 |
return segmentFor(hash).replace(key, hash, value);
|
|
990 |
}
|
|
991 |
|
|
992 |
/**
|
|
993 |
* Removes all of the mappings from this map.
|
|
994 |
*/
|
|
995 |
public void clear() {
|
|
996 |
for (int i = 0; i < segments.length; ++i)
|
|
997 |
segments[i].clear();
|
|
998 |
}
|
|
999 |
|
|
1000 |
/**
|
|
1001 |
* Returns a {@link Set} view of the keys contained in this map.
|
|
1002 |
* The set is backed by the map, so changes to the map are
|
|
1003 |
* reflected in the set, and vice-versa. The set supports element
|
|
1004 |
* removal, which removes the corresponding mapping from this map,
|
|
1005 |
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
|
|
1006 |
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
|
|
1007 |
* operations. It does not support the <tt>add</tt> or
|
|
1008 |
* <tt>addAll</tt> operations.
|
|
1009 |
*
|
|
1010 |
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
|
|
1011 |
* that will never throw {@link ConcurrentModificationException},
|
|
1012 |
* and guarantees to traverse elements as they existed upon
|
|
1013 |
* construction of the iterator, and may (but is not guaranteed to)
|
|
1014 |
* reflect any modifications subsequent to construction.
|
|
1015 |
*/
|
|
1016 |
public Set<K> keySet() {
|
|
1017 |
Set<K> ks = keySet;
|
|
1018 |
return (ks != null) ? ks : (keySet = new KeySet());
|
|
1019 |
}
|
|
1020 |
|
|
1021 |
/**
|
|
1022 |
* Returns a {@link Collection} view of the values contained in this map.
|
|
1023 |
* The collection is backed by the map, so changes to the map are
|
|
1024 |
* reflected in the collection, and vice-versa. The collection
|
|
1025 |
* supports element removal, which removes the corresponding
|
|
1026 |
* mapping from this map, via the <tt>Iterator.remove</tt>,
|
|
1027 |
* <tt>Collection.remove</tt>, <tt>removeAll</tt>,
|
|
1028 |
* <tt>retainAll</tt>, and <tt>clear</tt> operations. It does not
|
|
1029 |
* support the <tt>add</tt> or <tt>addAll</tt> operations.
|
|
1030 |
*
|
|
1031 |
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
|
|
1032 |
* that will never throw {@link ConcurrentModificationException},
|
|
1033 |
* and guarantees to traverse elements as they existed upon
|
|
1034 |
* construction of the iterator, and may (but is not guaranteed to)
|
|
1035 |
* reflect any modifications subsequent to construction.
|
|
1036 |
*/
|
|
1037 |
public Collection<V> values() {
|
|
1038 |
Collection<V> vs = values;
|
|
1039 |
return (vs != null) ? vs : (values = new Values());
|
|
1040 |
}
|
|
1041 |
|
|
1042 |
/**
|
|
1043 |
* Returns a {@link Set} view of the mappings contained in this map.
|
|
1044 |
* The set is backed by the map, so changes to the map are
|
|
1045 |
* reflected in the set, and vice-versa. The set supports element
|
|
1046 |
* removal, which removes the corresponding mapping from the map,
|
|
1047 |
* via the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
|
|
1048 |
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
|
|
1049 |
* operations. It does not support the <tt>add</tt> or
|
|
1050 |
* <tt>addAll</tt> operations.
|
|
1051 |
*
|
|
1052 |
* <p>The view's <tt>iterator</tt> is a "weakly consistent" iterator
|
|
1053 |
* that will never throw {@link ConcurrentModificationException},
|
|
1054 |
* and guarantees to traverse elements as they existed upon
|
|
1055 |
* construction of the iterator, and may (but is not guaranteed to)
|
|
1056 |
* reflect any modifications subsequent to construction.
|
|
1057 |
*/
|
|
1058 |
public Set<Map.Entry<K,V>> entrySet() {
|
|
1059 |
Set<Map.Entry<K,V>> es = entrySet;
|
|
1060 |
return (es != null) ? es : (entrySet = new EntrySet());
|
|
1061 |
}
|
|
1062 |
|
|
1063 |
/**
|
|
1064 |
* Returns an enumeration of the keys in this table.
|
|
1065 |
*
|
|
1066 |
* @return an enumeration of the keys in this table
|
|
1067 |
* @see #keySet()
|
|
1068 |
*/
|
|
1069 |
public Enumeration<K> keys() {
|
|
1070 |
return new KeyIterator();
|
|
1071 |
}
|
|
1072 |
|
|
1073 |
/**
|
|
1074 |
* Returns an enumeration of the values in this table.
|
|
1075 |
*
|
|
1076 |
* @return an enumeration of the values in this table
|
|
1077 |
* @see #values()
|
|
1078 |
*/
|
|
1079 |
public Enumeration<V> elements() {
|
|
1080 |
return new ValueIterator();
|
|
1081 |
}
|
|
1082 |
|
|
1083 |
/* ---------------- Iterator Support -------------- */
|
|
1084 |
|
|
1085 |
abstract class HashIterator {
|
|
1086 |
int nextSegmentIndex;
|
|
1087 |
int nextTableIndex;
|
|
1088 |
HashEntry<K,V>[] currentTable;
|
|
1089 |
HashEntry<K, V> nextEntry;
|
|
1090 |
HashEntry<K, V> lastReturned;
|
|
1091 |
|
|
1092 |
HashIterator() {
|
|
1093 |
nextSegmentIndex = segments.length - 1;
|
|
1094 |
nextTableIndex = -1;
|
|
1095 |
advance();
|
|
1096 |
}
|
|
1097 |
|
|
1098 |
public boolean hasMoreElements() { return hasNext(); }
|
|
1099 |
|
|
1100 |
final void advance() {
|
|
1101 |
if (nextEntry != null && (nextEntry = nextEntry.next) != null)
|
|
1102 |
return;
|
|
1103 |
|
|
1104 |
while (nextTableIndex >= 0) {
|
|
1105 |
if ( (nextEntry = currentTable[nextTableIndex--]) != null)
|
|
1106 |
return;
|
|
1107 |
}
|
|
1108 |
|
|
1109 |
while (nextSegmentIndex >= 0) {
|
|
1110 |
Segment<K,V> seg = segments[nextSegmentIndex--];
|
|
1111 |
if (seg.count != 0) {
|
|
1112 |
currentTable = seg.table;
|
|
1113 |
for (int j = currentTable.length - 1; j >= 0; --j) {
|
|
1114 |
if ( (nextEntry = currentTable[j]) != null) {
|
|
1115 |
nextTableIndex = j - 1;
|
|
1116 |
return;
|
|
1117 |
}
|
|
1118 |
}
|
|
1119 |
}
|
|
1120 |
}
|
|
1121 |
}
|
|
1122 |
|
|
1123 |
public boolean hasNext() { return nextEntry != null; }
|
|
1124 |
|
|
1125 |
HashEntry<K,V> nextEntry() {
|
|
1126 |
if (nextEntry == null)
|
|
1127 |
throw new NoSuchElementException();
|
|
1128 |
lastReturned = nextEntry;
|
|
1129 |
advance();
|
|
1130 |
return lastReturned;
|
|
1131 |
}
|
|
1132 |
|
|
1133 |
public void remove() {
|
|
1134 |
if (lastReturned == null)
|
|
1135 |
throw new IllegalStateException();
|
|
1136 |
ConcurrentHashMap.this.remove(lastReturned.key);
|
|
1137 |
lastReturned = null;
|
|
1138 |
}
|
|
1139 |
}
|
|
1140 |
|
|
1141 |
final class KeyIterator
|
|
1142 |
extends HashIterator
|
|
1143 |
implements Iterator<K>, Enumeration<K>
|
|
1144 |
{
|
|
1145 |
public K next() { return super.nextEntry().key; }
|
|
1146 |
public K nextElement() { return super.nextEntry().key; }
|
|
1147 |
}
|
|
1148 |
|
|
1149 |
final class ValueIterator
|
|
1150 |
extends HashIterator
|
|
1151 |
implements Iterator<V>, Enumeration<V>
|
|
1152 |
{
|
|
1153 |
public V next() { return super.nextEntry().value; }
|
|
1154 |
public V nextElement() { return super.nextEntry().value; }
|
|
1155 |
}
|
|
1156 |
|
|
1157 |
/**
|
|
1158 |
* Custom Entry class used by EntryIterator.next(), that relays
|
|
1159 |
* setValue changes to the underlying map.
|
|
1160 |
*/
|
|
1161 |
final class WriteThroughEntry
|
|
1162 |
extends AbstractMap.SimpleEntry<K,V>
|
|
1163 |
{
|
|
1164 |
WriteThroughEntry(K k, V v) {
|
|
1165 |
super(k,v);
|
|
1166 |
}
|
|
1167 |
|
|
1168 |
/**
|
|
1169 |
* Set our entry's value and write through to the map. The
|
|
1170 |
* value to return is somewhat arbitrary here. Since a
|
|
1171 |
* WriteThroughEntry does not necessarily track asynchronous
|
|
1172 |
* changes, the most recent "previous" value could be
|
|
1173 |
* different from what we return (or could even have been
|
|
1174 |
* removed in which case the put will re-establish). We do not
|
|
1175 |
* and cannot guarantee more.
|
|
1176 |
*/
|
|
1177 |
public V setValue(V value) {
|
|
1178 |
if (value == null) throw new NullPointerException();
|
|
1179 |
V v = super.setValue(value);
|
|
1180 |
ConcurrentHashMap.this.put(getKey(), value);
|
|
1181 |
return v;
|
|
1182 |
}
|
|
1183 |
}
|
|
1184 |
|
|
1185 |
final class EntryIterator
|
|
1186 |
extends HashIterator
|
|
1187 |
implements Iterator<Entry<K,V>>
|
|
1188 |
{
|
|
1189 |
public Map.Entry<K,V> next() {
|
|
1190 |
HashEntry<K,V> e = super.nextEntry();
|
|
1191 |
return new WriteThroughEntry(e.key, e.value);
|
|
1192 |
}
|
|
1193 |
}
|
|
1194 |
|
|
1195 |
final class KeySet extends AbstractSet<K> {
|
|
1196 |
public Iterator<K> iterator() {
|
|
1197 |
return new KeyIterator();
|
|
1198 |
}
|
|
1199 |
public int size() {
|
|
1200 |
return ConcurrentHashMap.this.size();
|
|
1201 |
}
|
|
1202 |
public boolean isEmpty() {
|
|
1203 |
return ConcurrentHashMap.this.isEmpty();
|
|
1204 |
}
|
|
1205 |
public boolean contains(Object o) {
|
|
1206 |
return ConcurrentHashMap.this.containsKey(o);
|
|
1207 |
}
|
|
1208 |
public boolean remove(Object o) {
|
|
1209 |
return ConcurrentHashMap.this.remove(o) != null;
|
|
1210 |
}
|
|
1211 |
public void clear() {
|
|
1212 |
ConcurrentHashMap.this.clear();
|
|
1213 |
}
|
|
1214 |
}
|
|
1215 |
|
|
1216 |
final class Values extends AbstractCollection<V> {
|
|
1217 |
public Iterator<V> iterator() {
|
|
1218 |
return new ValueIterator();
|
|
1219 |
}
|
|
1220 |
public int size() {
|
|
1221 |
return ConcurrentHashMap.this.size();
|
|
1222 |
}
|
|
1223 |
public boolean isEmpty() {
|
|
1224 |
return ConcurrentHashMap.this.isEmpty();
|
|
1225 |
}
|
|
1226 |
public boolean contains(Object o) {
|
|
1227 |
return ConcurrentHashMap.this.containsValue(o);
|
|
1228 |
}
|
|
1229 |
public void clear() {
|
|
1230 |
ConcurrentHashMap.this.clear();
|
|
1231 |
}
|
|
1232 |
}
|
|
1233 |
|
|
1234 |
final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
|
|
1235 |
public Iterator<Map.Entry<K,V>> iterator() {
|
|
1236 |
return new EntryIterator();
|
|
1237 |
}
|
|
1238 |
public boolean contains(Object o) {
|
|
1239 |
if (!(o instanceof Map.Entry))
|
|
1240 |
return false;
|
|
1241 |
Map.Entry<?,?> e = (Map.Entry<?,?>)o;
|
|
1242 |
V v = ConcurrentHashMap.this.get(e.getKey());
|
|
1243 |
return v != null && v.equals(e.getValue());
|
|
1244 |
}
|
|
1245 |
public boolean remove(Object o) {
|
|
1246 |
if (!(o instanceof Map.Entry))
|
|
1247 |
return false;
|
|
1248 |
Map.Entry<?,?> e = (Map.Entry<?,?>)o;
|
|
1249 |
return ConcurrentHashMap.this.remove(e.getKey(), e.getValue());
|
|
1250 |
}
|
|
1251 |
public int size() {
|
|
1252 |
return ConcurrentHashMap.this.size();
|
|
1253 |
}
|
|
1254 |
public boolean isEmpty() {
|
|
1255 |
return ConcurrentHashMap.this.isEmpty();
|
|
1256 |
}
|
|
1257 |
public void clear() {
|
|
1258 |
ConcurrentHashMap.this.clear();
|
|
1259 |
}
|
|
1260 |
}
|
|
1261 |
|
|
1262 |
/* ---------------- Serialization Support -------------- */
|
|
1263 |
|
|
1264 |
/**
|
|
1265 |
* Save the state of the <tt>ConcurrentHashMap</tt> instance to a
|
|
1266 |
* stream (i.e., serialize it).
|
|
1267 |
* @param s the stream
|
|
1268 |
* @serialData
|
|
1269 |
* the key (Object) and value (Object)
|
|
1270 |
* for each key-value mapping, followed by a null pair.
|
|
1271 |
* The key-value mappings are emitted in no particular order.
|
|
1272 |
*/
|
|
1273 |
private void writeObject(java.io.ObjectOutputStream s) throws IOException {
|
|
1274 |
s.defaultWriteObject();
|
|
1275 |
|
|
1276 |
for (int k = 0; k < segments.length; ++k) {
|
|
1277 |
Segment<K,V> seg = segments[k];
|
|
1278 |
seg.lock();
|
|
1279 |
try {
|
|
1280 |
HashEntry<K,V>[] tab = seg.table;
|
|
1281 |
for (int i = 0; i < tab.length; ++i) {
|
|
1282 |
for (HashEntry<K,V> e = tab[i]; e != null; e = e.next) {
|
|
1283 |
s.writeObject(e.key);
|
|
1284 |
s.writeObject(e.value);
|
|
1285 |
}
|
|
1286 |
}
|
|
1287 |
} finally {
|
|
1288 |
seg.unlock();
|
|
1289 |
}
|
|
1290 |
}
|
|
1291 |
s.writeObject(null);
|
|
1292 |
s.writeObject(null);
|
|
1293 |
}
|
|
1294 |
|
|
1295 |
/**
|
|
1296 |
* Reconstitute the <tt>ConcurrentHashMap</tt> instance from a
|
|
1297 |
* stream (i.e., deserialize it).
|
|
1298 |
* @param s the stream
|
|
1299 |
*/
|
|
1300 |
private void readObject(java.io.ObjectInputStream s)
|
|
1301 |
throws IOException, ClassNotFoundException {
|
|
1302 |
s.defaultReadObject();
|
|
1303 |
|
|
1304 |
// Initialize each segment to be minimally sized, and let grow.
|
|
1305 |
for (int i = 0; i < segments.length; ++i) {
|
|
1306 |
segments[i].setTable(new HashEntry[1]);
|
|
1307 |
}
|
|
1308 |
|
|
1309 |
// Read the keys and values, and put the mappings in the table
|
|
1310 |
for (;;) {
|
|
1311 |
K key = (K) s.readObject();
|
|
1312 |
V value = (V) s.readObject();
|
|
1313 |
if (key == null)
|
|
1314 |
break;
|
|
1315 |
put(key, value);
|
|
1316 |
}
|
|
1317 |
}
|
|
1318 |
}
|