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@@ -1,37 +1,3 @@
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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. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* 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/publicdomain/zero/1.0/
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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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@@ -41,64 +7,6 @@ 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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