jtulach@1334: /*
jtulach@1334:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
jtulach@1334:  *
jtulach@1334:  * This code is free software; you can redistribute it and/or modify it
jtulach@1334:  * under the terms of the GNU General Public License version 2 only, as
jtulach@1334:  * published by the Free Software Foundation.  Oracle designates this
jtulach@1334:  * particular file as subject to the "Classpath" exception as provided
jtulach@1334:  * by Oracle in the LICENSE file that accompanied this code.
jtulach@1334:  *
jtulach@1334:  * This code is distributed in the hope that it will be useful, but WITHOUT
jtulach@1334:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
jtulach@1334:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
jtulach@1334:  * version 2 for more details (a copy is included in the LICENSE file that
jtulach@1334:  * accompanied this code).
jtulach@1334:  *
jtulach@1334:  * You should have received a copy of the GNU General Public License version
jtulach@1334:  * 2 along with this work; if not, write to the Free Software Foundation,
jtulach@1334:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
jtulach@1334:  *
jtulach@1334:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
jtulach@1334:  * or visit www.oracle.com if you need additional information or have any
jtulach@1334:  * questions.
jtulach@1334:  */
jtulach@1334: 
jtulach@1334: /*
jtulach@1334:  * This file is available under and governed by the GNU General Public
jtulach@1334:  * License version 2 only, as published by the Free Software Foundation.
jtulach@1334:  * However, the following notice accompanied the original version of this
jtulach@1334:  * file:
jtulach@1334:  *
jtulach@1334:  * Written by Doug Lea with assistance from members of JCP JSR-166
jtulach@1334:  * Expert Group and released to the public domain, as explained at
jtulach@1334:  * http://creativecommons.org/publicdomain/zero/1.0/
jtulach@1334:  */
jaroslav@1338: package java.util.concurrent;
jtulach@1334: 
jtulach@1334: import java.util.*;
jtulach@1334: import java.io.Serializable;
jtulach@1334: import java.io.IOException;
jtulach@1334: import java.io.ObjectInputStream;
jtulach@1334: import java.io.ObjectOutputStream;
jtulach@1334: 
jtulach@1334: /**
jaroslav@1338:  * A hash table supporting full concurrency of retrievals and adjustable
jaroslav@1338:  * expected concurrency for updates. This class obeys the same functional
jaroslav@1338:  * specification as {@link java.util.Hashtable}, and includes versions of
jaroslav@1338:  * methods corresponding to each method of
jaroslav@1338:  * <tt>Hashtable</tt>. However, even though all operations are thread-safe,
jaroslav@1338:  * retrieval operations do <em>not</em> entail locking, and there is
jaroslav@1338:  * <em>not</em> any support for locking the entire table in a way that prevents
jaroslav@1338:  * all access. This class is fully interoperable with <tt>Hashtable</tt> in
jaroslav@1338:  * programs that rely on its thread safety but not on its synchronization
jaroslav@1338:  * details.
jtulach@1334:  *
jaroslav@1338:  * <p>
jaroslav@1338:  * Retrieval operations (including <tt>get</tt>) generally do not block, so may
jaroslav@1338:  * overlap with update operations (including
jaroslav@1338:  * <tt>put</tt> and <tt>remove</tt>). Retrievals reflect the results of the most
jaroslav@1338:  * recently <em>completed</em> update operations holding upon their onset. For
jaroslav@1338:  * aggregate operations such as <tt>putAll</tt>
jaroslav@1338:  * and <tt>clear</tt>, concurrent retrievals may reflect insertion or removal of
jaroslav@1338:  * only some entries. Similarly, Iterators and Enumerations return elements
jaroslav@1338:  * reflecting the state of the hash table at some point at or since the creation
jaroslav@1338:  * of the iterator/enumeration. They do <em>not</em> throw
jaroslav@1338:  * {@link ConcurrentModificationException}. However, iterators are designed to
jaroslav@1338:  * be used by only one thread at a time.
jtulach@1334:  *
jaroslav@1338:  * <p>
jaroslav@1338:  * The allowed concurrency among update operations is guided by the optional
jaroslav@1338:  * <tt>concurrencyLevel</tt> constructor argument (default <tt>16</tt>), which
jaroslav@1338:  * is used as a hint for internal sizing. The table is internally partitioned to
jaroslav@1338:  * try to permit the indicated number of concurrent updates without contention.
jaroslav@1338:  * Because placement in hash tables is essentially random, the actual
jaroslav@1338:  * concurrency will vary. Ideally, you should choose a value to accommodate as
jaroslav@1338:  * many threads as will ever concurrently modify the table. Using a
jaroslav@1338:  * significantly higher value than you need can waste space and time, and a
jaroslav@1338:  * significantly lower value can lead to thread contention. But overestimates
jaroslav@1338:  * and underestimates within an order of magnitude do not usually have much
jaroslav@1338:  * noticeable impact. A value of one is appropriate when it is known that only
jaroslav@1338:  * one thread will modify and all others will only read. Also, resizing this or
jaroslav@1338:  * any other kind of hash table is a relatively slow operation, so, when
jaroslav@1338:  * possible, it is a good idea to provide estimates of expected table sizes in
jtulach@1334:  * constructors.
jtulach@1334:  *
jaroslav@1338:  * <p>
jaroslav@1338:  * This class and its views and iterators implement all of the
jaroslav@1338:  * <em>optional</em> methods of the {@link Map} and {@link Iterator} interfaces.
jtulach@1334:  *
jaroslav@1338:  * <p>
jaroslav@1338:  * Like {@link Hashtable} but unlike {@link HashMap}, this class does
jaroslav@1338:  * <em>not</em> allow <tt>null</tt> to be used as a key or value.
jtulach@1334:  *
jaroslav@1338:  * <p>
jaroslav@1338:  * This class is a member of the
jtulach@1334:  * <a href="{@docRoot}/../technotes/guides/collections/index.html">
jtulach@1334:  * Java Collections Framework</a>.
jtulach@1334:  *
jtulach@1334:  * @since 1.5
jtulach@1334:  * @author Doug Lea
jtulach@1334:  * @param <K> the type of keys maintained by this map
jtulach@1334:  * @param <V> the type of mapped values
jtulach@1334:  */
jtulach@1334: public class ConcurrentHashMap<K, V> extends AbstractMap<K, V>
jaroslav@1338:     implements ConcurrentMap<K, V>, Serializable {
jaroslav@1338: 
jtulach@1334:     private static final long serialVersionUID = 7249069246763182397L;
jtulach@1334:     /**
jtulach@1334:      * The default initial capacity for this table,
jtulach@1334:      * used when not otherwise specified in a constructor.
jtulach@1334:      */
jtulach@1334:     static final int DEFAULT_INITIAL_CAPACITY = 16;
jtulach@1334: 
jtulach@1334:     /**
jtulach@1334:      * The default load factor for this table, used when not
jtulach@1334:      * otherwise specified in a constructor.
jtulach@1334:      */
jtulach@1334:     static final float DEFAULT_LOAD_FACTOR = 0.75f;
jtulach@1334: 
jtulach@1334:     /**
jtulach@1334:      * The default concurrency level for this table, used when not
jtulach@1334:      * otherwise specified in a constructor.
jtulach@1334:      */
jtulach@1334:     static final int DEFAULT_CONCURRENCY_LEVEL = 16;
jtulach@1334: 
jaroslav@1338:     private final Map<K, V> delegate;
jtulach@1334: 
jtulach@1334: 
jtulach@1334:     /**
jtulach@1334:      * Creates a new, empty map with the specified initial
jtulach@1334:      * capacity, load factor and concurrency level.
jtulach@1334:      *
jtulach@1334:      * @param initialCapacity the initial capacity. The implementation
jtulach@1334:      * performs internal sizing to accommodate this many elements.
jtulach@1334:      * @param loadFactor  the load factor threshold, used to control resizing.
jtulach@1334:      * Resizing may be performed when the average number of elements per
jtulach@1334:      * bin exceeds this threshold.
jtulach@1334:      * @param concurrencyLevel the estimated number of concurrently
jtulach@1334:      * updating threads. The implementation performs internal sizing
jtulach@1334:      * to try to accommodate this many threads.
jtulach@1334:      * @throws IllegalArgumentException if the initial capacity is
jtulach@1334:      * negative or the load factor or concurrencyLevel are
jtulach@1334:      * nonpositive.
jtulach@1334:      */
jtulach@1334:     @SuppressWarnings("unchecked")
jtulach@1334:     public ConcurrentHashMap(int initialCapacity,
jtulach@1334:                              float loadFactor, int concurrencyLevel) {
jtulach@1334:         if (!(loadFactor > 0) || initialCapacity < 0 || concurrencyLevel <= 0)
jtulach@1334:             throw new IllegalArgumentException();
jaroslav@1338:         delegate = new HashMap<>(initialCapacity, loadFactor);
jtulach@1334:     }
jtulach@1334: 
jtulach@1334:     /**
jtulach@1334:      * Creates a new, empty map with the specified initial capacity
jtulach@1334:      * and load factor and with the default concurrencyLevel (16).
jtulach@1334:      *
jtulach@1334:      * @param initialCapacity The implementation performs internal
jtulach@1334:      * sizing to accommodate this many elements.
jtulach@1334:      * @param loadFactor  the load factor threshold, used to control resizing.
jtulach@1334:      * Resizing may be performed when the average number of elements per
jtulach@1334:      * bin exceeds this threshold.
jtulach@1334:      * @throws IllegalArgumentException if the initial capacity of
jtulach@1334:      * elements is negative or the load factor is nonpositive
jtulach@1334:      *
jtulach@1334:      * @since 1.6
jtulach@1334:      */
jtulach@1334:     public ConcurrentHashMap(int initialCapacity, float loadFactor) {
jtulach@1334:         this(initialCapacity, loadFactor, DEFAULT_CONCURRENCY_LEVEL);
jtulach@1334:     }
jtulach@1334: 
jtulach@1334:     /**
jtulach@1334:      * Creates a new, empty map with the specified initial capacity,
jtulach@1334:      * and with default load factor (0.75) and concurrencyLevel (16).
jtulach@1334:      *
jtulach@1334:      * @param initialCapacity the initial capacity. The implementation
jtulach@1334:      * performs internal sizing to accommodate this many elements.
jtulach@1334:      * @throws IllegalArgumentException if the initial capacity of
jtulach@1334:      * elements is negative.
jtulach@1334:      */
jtulach@1334:     public ConcurrentHashMap(int initialCapacity) {
jtulach@1334:         this(initialCapacity, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
jtulach@1334:     }
jtulach@1334: 
jtulach@1334:     /**
jtulach@1334:      * Creates a new, empty map with a default initial capacity (16),
jtulach@1334:      * load factor (0.75) and concurrencyLevel (16).
jtulach@1334:      */
jtulach@1334:     public ConcurrentHashMap() {
jtulach@1334:         this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
jtulach@1334:     }
jtulach@1334: 
jtulach@1334:     /**
jtulach@1334:      * Creates a new map with the same mappings as the given map.
jtulach@1334:      * The map is created with a capacity of 1.5 times the number
jtulach@1334:      * of mappings in the given map or 16 (whichever is greater),
jtulach@1334:      * and a default load factor (0.75) and concurrencyLevel (16).
jtulach@1334:      *
jtulach@1334:      * @param m the map
jtulach@1334:      */
jtulach@1334:     public ConcurrentHashMap(Map<? extends K, ? extends V> m) {
jtulach@1334:         this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
jtulach@1334:                       DEFAULT_INITIAL_CAPACITY),
jtulach@1334:              DEFAULT_LOAD_FACTOR, DEFAULT_CONCURRENCY_LEVEL);
jtulach@1334:         putAll(m);
jtulach@1334:     }
jaroslav@1338:     
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public int size() {
jaroslav@1338:         return delegate.size();
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public boolean isEmpty() {
jaroslav@1338:         return delegate.isEmpty();
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public boolean containsKey(Object key) {
jaroslav@1338:         return delegate.containsKey(key);
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public boolean containsValue(Object value) {
jaroslav@1338:         return delegate.containsValue(value);
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public V get(Object key) {
jaroslav@1338:         return delegate.get(key);
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public V put(K key, V value) {
jaroslav@1338:         return delegate.put(key, value);
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public V remove(Object key) {
jaroslav@1338:         return delegate.remove(key);
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public void putAll(Map<? extends K, ? extends V> m) {
jaroslav@1338:         delegate.putAll(m);
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public void clear() {
jaroslav@1338:         delegate.clear();
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public Set<K> keySet() {
jaroslav@1338:         return delegate.keySet();
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public Collection<V> values() {
jaroslav@1338:         return delegate.values();
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public Set<Entry<K, V>> entrySet() {
jaroslav@1338:         return delegate.entrySet();
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public boolean equals(Object o) {
jaroslav@1338:         return delegate.equals(o);
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public int hashCode() {
jaroslav@1338:         return delegate.hashCode();
jaroslav@1338:     }
jaroslav@1338: 
jaroslav@1338:     @Override
jaroslav@1338:     public String toString() {
jaroslav@1338:         return delegate.toString();
jaroslav@1338:     }
jaroslav@1338: 
jaroslav@1338:     @Override
jaroslav@1338:     public V putIfAbsent(K key, V value) {
jaroslav@1338:         V old = delegate.get(key);
jaroslav@1338:         if (old == null) {
jaroslav@1338:             return delegate.put(key, value);
jaroslav@1338:         }
jaroslav@1338:         return old;
jaroslav@1338:     }
jaroslav@1338: 
jaroslav@1338:     @Override
jaroslav@1338:     public boolean remove(Object key, Object value) {
jaroslav@1338:         if (equals(value, delegate.get(key))) {
jaroslav@1338:             delegate.remove(key);
jaroslav@1338:             return true;
jaroslav@1338:         } else {
jaroslav@1338:             return false;
jtulach@1334:         }
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public boolean replace(K key, V oldValue, V newValue) {
jaroslav@1338:         if (equals(oldValue, delegate.get(key))) {
jaroslav@1338:             delegate.put(key, newValue);
jaroslav@1338:             return true;
jaroslav@1338:         } else {
jaroslav@1338:             return false;
jtulach@1334:         }
jtulach@1334:     }
jtulach@1334: 
jaroslav@1338:     @Override
jaroslav@1338:     public V replace(K key, V value) {
jaroslav@1338:         if (delegate.containsKey(key)) {
jaroslav@1338:             return delegate.put(key, value);
jaroslav@1338:         } else {
jaroslav@1338:             return null;
jtulach@1334:         }
jtulach@1334:     }
jaroslav@1338:     
jaroslav@1338:     private static boolean equals(Object a, Object b) {
jaroslav@1338:         if (a == null) {
jaroslav@1338:             return b == null;
jaroslav@1338:         } else {
jaroslav@1338:             return a.equals(b);
jtulach@1334:         }
jtulach@1334:     }
jtulach@1334: }