mirror of https://github.com/apache/openjpa.git
OPENJPA-637. Reverting ConcurrentHashMap implementation per the patch provided by Jeremy Bauer. A more complete, configurable implementation is being tracked via the related sub-task OPENJPA-643.
git-svn-id: https://svn.apache.org/repos/asf/openjpa/trunk@672003 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Kevin W. Sutter
parent
976a5e1faf
commit
82e61ba0d5
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@ -22,7 +22,6 @@ import java.util.AbstractCollection;
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import java.util.AbstractSet;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.Iterator;
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import java.util.Map;
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import java.util.Set;
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@ -31,12 +30,10 @@ import org.apache.commons.collections.Predicate;
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import org.apache.commons.collections.iterators.FilterIterator;
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import org.apache.commons.collections.iterators.IteratorChain;
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import org.apache.openjpa.lib.util.LRUMap;
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import org.apache.openjpa.lib.util.ReferenceHashMap;
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import org.apache.openjpa.lib.util.ReferenceMap;
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import org.apache.openjpa.lib.util.SizedMap;
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import org.apache.openjpa.lib.util.concurrent.ConcurrentHashMap;
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import org.apache.openjpa.lib.util.concurrent.ConcurrentReferenceHashMap;
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import org.apache.openjpa.lib.util.concurrent.NullSafeConcurrentHashMap;
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import org.apache.openjpa.lib.util.concurrent.SizedConcurrentHashMap;
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import java.util.concurrent.locks.ReentrantLock;
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@ -114,10 +111,10 @@ public class CacheMap
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softMapValueExpired(key);
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}
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};
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pinnedMap = new NullSafeConcurrentHashMap();
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pinnedMap = new ConcurrentHashMap();
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if (!lru) {
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cacheMap = new SizedConcurrentHashMap(size, load, concurrencyLevel){
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cacheMap = new ConcurrentHashMap(size, load) {
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public void overflowRemoved(Object key, Object value) {
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cacheMapOverflowRemoved(key, value);
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}
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@ -0,0 +1,941 @@
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/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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package org.apache.openjpa.lib.util.concurrent;
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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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import java.io.Serializable;
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import java.util.AbstractCollection;
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import java.util.AbstractMap;
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import java.util.AbstractSet;
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import java.util.Collection;
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import java.util.Iterator;
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import java.util.Map;
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import java.util.NoSuchElementException;
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import java.util.Random;
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import java.util.Set;
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import org.apache.openjpa.lib.util.SizedMap;
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/**
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* This class implements a HashMap which has limited synchronization.
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* In particular mutators are generally synchronized while accessors
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* are generally not. Additionally the Iterators returned by this
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* class are not "fail-fast", but instead try to continue to iterate
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* over the data structure after changes have been made.
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* The synchronization semantics are built right in to the
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* implementation rather than using a delegating wrapper like the
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* other collection classes do because it wasn't clear to me that the
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* how the two should be seperated or that it would be useful to do
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* so. This can probably be a topic for further debate in the future.
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* This class is based heavily on the HashMap class in the Java
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* collections package.
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*/
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public class ConcurrentHashMap extends AbstractMap
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implements ConcurrentMap, SizedMap, Cloneable, Serializable {
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/**
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* The default initial capacity - MUST be a power of two.
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*/
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private static final int DEFAULT_INITIAL_CAPACITY = 16;
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/**
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* The maximum capacity, used if a higher value is implicitly specified
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* by either of the constructors with arguments.
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* MUST be a power of two <= 1<<30.
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*/
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private static final int MAXIMUM_CAPACITY = 1 << 30;
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/**
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* The load fast used when none specified in constructor.
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*/
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private static final float DEFAULT_LOAD_FACTOR = 0.75f;
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/**
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* Cache of random numbers used in "random" methods, since generating them
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* is expensive. We hope each map changes enough between cycling through
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* this list that the overall effect is random enough.
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*/
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static final double[] RANDOMS = new double[1000];
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static {
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Random random = new Random();
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for (int i = 0; i < RANDOMS.length; i++)
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RANDOMS[i] = random.nextDouble();
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}
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/**
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* The table, resized as necessary. Length MUST Always be a power of two.
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*/
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private transient Entry[] table;
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/**
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* The number of key-value mappings contained in this identity hash map.
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*/
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private transient int size;
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/**
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* The next size value at which to resize(capacity * load factor).
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*
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* @serial
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*/
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private int threshold;
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/**
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* The load factor for the hash table.
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*
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* @serial
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*/
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private final float loadFactor;
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/**
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* Spread "random" removes and iteration.
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*/
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private int randomEntry = 0;
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/**
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* Maximum entries.
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*/
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private int maxSize = Integer.MAX_VALUE;
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/**
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* Constructs an empty <tt>ConcurrentHashMap</tt> with the specified initial
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* capacity and load factor.
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*
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* @param initialCapacity The initial capacity.
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* @param loadFactor The load factor.
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* @throws IllegalArgumentException if the initial capacity is negative
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* or the load factor is nonpositive.
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*/
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public ConcurrentHashMap(int initialCapacity, float loadFactor) {
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if (initialCapacity < 0) {
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throw new IllegalArgumentException("Illegal initial capacity: " +
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initialCapacity);
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}
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if (initialCapacity > MAXIMUM_CAPACITY)
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initialCapacity = MAXIMUM_CAPACITY;
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if (loadFactor <= 0 || loadFactor > 1) {
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throw new IllegalArgumentException("Illegal load factor: " +
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loadFactor);
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}
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// Find a power of 2 >= initialCapacity
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int capacity = 1;
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while (capacity < initialCapacity) capacity <<= 1;
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this.loadFactor = loadFactor;
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threshold = (int) (capacity * loadFactor);
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table = new Entry[capacity];
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}
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/**
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* Constructs an empty <tt>ConcurrentHashMap</tt> with the specified initial
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* capacity and the default load factor(0.75).
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*
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* @param initialCapacity the initial capacity.
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* @throws IllegalArgumentException if the initial capacity is negative.
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*/
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public ConcurrentHashMap(int initialCapacity) {
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this(initialCapacity, DEFAULT_LOAD_FACTOR);
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}
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/**
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* Constructs an empty <tt>ConcurrentHashMap</tt> with the default initial
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* capacity(16) and the default load factor(0.75).
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*/
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public ConcurrentHashMap() {
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this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
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}
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/**
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* Constructs a new <tt>ConcurrentHashMap</tt> with the same mappings as the
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* specified <tt>Map</tt>. The <tt>ConcurrentHashMap</tt> is created with
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* default load factor(0.75) and an initial capacity sufficient to
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* hold the mappings in the specified <tt>Map</tt>.
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*
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* @param m the map whose mappings are to be placed in this map.
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* @throws NullPointerException if the specified map is null.
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*/
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public ConcurrentHashMap(Map m) {
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this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
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DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
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putAll(m);
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}
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// internal utilities
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/**
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* Value representing null keys inside tables.
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*/
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private static final Object NULL_KEY = new Object();
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/**
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* Returns internal representation for key. Use NULL_KEY if key is null.
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*/
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private static Object maskNull(Object key) {
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return (key == null ? NULL_KEY : key);
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}
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/**
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* Returns key represented by specified internal representation.
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*/
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private static Object unmaskNull(Object key) {
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return (key == NULL_KEY ? null : key);
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}
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/**
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* Returns a hash code for non-null Object x.
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*/
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private static int hash(Object x) {
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int h = x.hashCode();
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return h - (h << 7); // i.e., -127 * h
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}
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/**
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* Check for equality of non-null reference x and possibly-null y.
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*/
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private static boolean eq(Object x, Object y) {
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return x == y || x.equals(y);
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}
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/**
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* Returns the current capacity of backing table in this map.
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*
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* @return the current capacity of backing table in this map.
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*/
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public final int capacity() {
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return table.length;
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}
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/**
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* Returns the load factor for this map.
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*
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* @return the load factor for this map.
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*/
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public final float loadFactor() {
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return loadFactor;
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}
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public int getMaxSize() {
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return maxSize;
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}
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public void setMaxSize(int maxSize) {
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this.maxSize = (maxSize < 0) ? Integer.MAX_VALUE : maxSize;
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if (this.maxSize != Integer.MAX_VALUE)
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removeOverflow(this.maxSize);
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}
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public boolean isFull() {
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return maxSize != Integer.MAX_VALUE && size() >= maxSize;
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}
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public void overflowRemoved(Object key, Object value) {
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}
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/**
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* Returns the number of key-value mappings in this map.
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*
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* @return the number of key-value mappings in this map.
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*/
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public final int size() {
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return size;
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}
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/**
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* Returns <tt>true</tt> if this map contains no key-value mappings.
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*
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* @return <tt>true</tt> if this map contains no key-value mappings.
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*/
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public final boolean isEmpty() {
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return size == 0;
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}
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/**
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* Returns the value to which the specified key is mapped in this identity
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* hash map, or <tt>null</tt> if the map contains no mapping for this key.
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* A return value of <tt>null</tt> does not <i>necessarily</i> indicate
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* that the map contains no mapping for the key; it is also possible that
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* the map explicitly maps the key to <tt>null</tt>. The
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* <tt>containsKey</tt> method may be used to distinguish these two cases.
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*
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* @param key the key whose associated value is to be returned.
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* @return the value to which this map maps the specified key, or
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* <tt>null</tt> if the map contains no mapping for this key.
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* @see #put(Object, Object)
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*/
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public Object get(Object key) {
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Entry e = getEntry(key);
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return e == null ? null : e.value;
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}
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/**
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* Returns <tt>true</tt> if this map contains a mapping for the
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* specified key.
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*
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* @param key The key whose presence in this map is to be tested
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* @return <tt>true</tt> if this map contains a mapping for the specified
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* key.
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*/
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public final boolean containsKey(Object key) {
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return getEntry(key) != null;
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}
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/**
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* Returns the entry associated with the specified key in the
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* ConcurrentHashMap. Returns null if the ConcurrentHashMap contains no
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* mapping for this key.
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*/
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protected Entry getEntry(Object key) {
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Object k = maskNull(key);
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int hash = hash(k);
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Entry[] tab = table;
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for (Entry e = tab[hash & (tab.length - 1)]; e != null; e = e.next) {
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if (e.hash == hash && eq(k, e.key)) return e;
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}
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return null;
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}
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/**
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* Associates the specified value with the specified key in this map.
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* If the map previously contained a mapping for this key, the old
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* value is replaced.
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*
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* @param key key with which the specified value is to be associated.
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* @param value value to be associated with the specified key.
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* @return previous value associated with specified key, or <tt>null</tt>
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* if there was no mapping for key. A <tt>null</tt> return can
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* also indicate that the ConcurrentHashMap previously associated
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* <tt>null</tt> with the specified key.
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*/
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public Object put(Object key, Object value) {
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Object k = maskNull(key);
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int hash = hash(k);
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synchronized (this) {
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int i = hash & (table.length - 1);
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for (Entry e = table[i]; e != null; e = e.next) {
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if (e.hash == hash && eq(k, e.key)) {
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Object oldValue = e.value;
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e.value = value;
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return oldValue;
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}
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}
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if (maxSize != Integer.MAX_VALUE)
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removeOverflow(maxSize - 1);
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table[i] = createEntry(hash, k, value, table[i]);
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if (size++ >= threshold) resize(2 * table.length);
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}
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return null;
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}
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/**
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* Remove any entries equal to or over the max size.
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*/
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private void removeOverflow(int maxSize) {
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while (size > maxSize) {
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Map.Entry entry = removeRandom();
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if (entry == null)
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break;
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overflowRemoved(entry.getKey(), entry.getValue());
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}
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}
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public Object putIfAbsent(Object key, Object value) {
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Object k = maskNull(key);
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int hash = hash(k);
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synchronized (this) {
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int i = hash & (table.length - 1);
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for (Entry e = table[i]; e != null; e = e.next) {
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if (e.hash == hash && eq(k, e.key)) {
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return e.value;
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}
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}
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if (maxSize != Integer.MAX_VALUE)
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removeOverflow(maxSize - 1);
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table[i] = createEntry(hash, k, value, table[i]);
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if (size++ >= threshold) resize(2 * table.length);
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}
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return null;
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}
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/**
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* Rehashes the contents of this map into a new <tt>ConcurrentHashMap</tt>
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* instance with a larger capacity. This method is called automatically when
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* the number of keys in this map exceeds its capacity and load factor.
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*
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* @param newCapacity the new capacity, MUST be a power of two.
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*/
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private void resize(int newCapacity) {
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// assert(newCapacity & -newCapacity) == newCapacity; // power of 2
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Entry[] oldTable = table;
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int oldCapacity = oldTable.length;
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// check if needed
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if (size < threshold || oldCapacity > newCapacity) return;
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Entry[] newTable = new Entry[newCapacity];
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int mask = newCapacity - 1;
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for (int i = oldCapacity; i-- > 0;) {
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for (Entry e = oldTable[i]; e != null; e = e.next) {
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Entry clone = (Entry) e.clone();
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int j = clone.hash & mask;
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clone.next = newTable[j];
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newTable[j] = clone;
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}
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}
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table = newTable;
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threshold = (int) (newCapacity * loadFactor);
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}
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/**
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* Copies all of the mappings from the specified map to this map
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* These mappings will replace any mappings that
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* this map had for any of the keys currently in the specified map.
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*
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* @param t mappings to be stored in this map.
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* @throws NullPointerException if the specified map is null.
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*/
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public final synchronized void putAll(Map t) {
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// Expand enough to hold t's elements without resizing.
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int n = t.size();
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if (n == 0) return;
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if (n >= threshold) {
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n = (int) (n / loadFactor + 1);
|
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if (n > MAXIMUM_CAPACITY) n = MAXIMUM_CAPACITY;
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int capacity = table.length;
|
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while (capacity < n) capacity <<= 1;
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resize(capacity);
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}
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|
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for (Iterator i = t.entrySet().iterator(); i.hasNext();) {
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Map.Entry e = (Map.Entry) i.next();
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put(e.getKey(), e.getValue());
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}
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}
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/**
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* Removes the mapping for this key from this map if present.
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*
|
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* @param key key whose mapping is to be removed from the map.
|
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* @return previous value associated with specified key, or <tt>null</tt>
|
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* if there was no mapping for key. A <tt>null</tt> return can
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* also indicate that the map previously associated <tt>null</tt>
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* with the specified key.
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*/
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public Object remove(Object key) {
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Entry e = removeEntryForKey(key);
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return (e == null ? e : e.value);
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}
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/**
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* Removes and returns the entry associated with the specified key in the
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* ConcurrentHashMap. Returns null if the ConcurrentHashMap contains no
|
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* mapping for this key.
|
||||
*/
|
||||
private Entry removeEntryForKey(Object key) {
|
||||
Object k = maskNull(key);
|
||||
int hash = hash(k);
|
||||
synchronized (this) {
|
||||
int i = hash & (table.length - 1);
|
||||
Entry e = table[i];
|
||||
|
||||
if (e == null) return null;
|
||||
if (e.hash == hash && eq(k, e.key)) {
|
||||
size--;
|
||||
table[i] = e.next;
|
||||
return e;
|
||||
}
|
||||
|
||||
Entry prev = e;
|
||||
for (e = e.next; e != null; prev = e, e = e.next) {
|
||||
if (e.hash == hash && eq(k, e.key)) {
|
||||
size--;
|
||||
prev.next = e.next;
|
||||
return e;
|
||||
}
|
||||
}
|
||||
}
|
||||
return null;
|
||||
}
|
||||
|
||||
/**
|
||||
* Special version of remove for EntrySet.
|
||||
*/
|
||||
private Entry removeMapping(Object o) {
|
||||
if (!(o instanceof Map.Entry)) return null;
|
||||
|
||||
Map.Entry entry = (Map.Entry) o;
|
||||
Object k = maskNull(entry.getKey());
|
||||
int hash = hash(k);
|
||||
synchronized (this) {
|
||||
int i = hash & (table.length - 1);
|
||||
Entry e = table[i];
|
||||
|
||||
if (e == null) return null;
|
||||
if (e.hash == hash && e.equals(entry)) {
|
||||
size--;
|
||||
table[i] = e.next;
|
||||
return e;
|
||||
}
|
||||
|
||||
Entry prev = e;
|
||||
for (e = e.next; e != null; prev = e, e = e.next) {
|
||||
if (e.hash == hash && e.equals(entry)) {
|
||||
size--;
|
||||
prev.next = e.next;
|
||||
return e;
|
||||
}
|
||||
}
|
||||
}
|
||||
return null;
|
||||
}
|
||||
|
||||
/**
|
||||
* Removes all mappings from this map.
|
||||
*/
|
||||
public synchronized void clear() {
|
||||
table = new Entry[table.length];
|
||||
size = 0;
|
||||
}
|
||||
|
||||
/**
|
||||
* Return an arbitrary entry index.
|
||||
*/
|
||||
private int randomEntryIndex() {
|
||||
if (randomEntry == RANDOMS.length)
|
||||
randomEntry = 0;
|
||||
return (int) (RANDOMS[randomEntry++] * table.length);
|
||||
}
|
||||
|
||||
public Map.Entry removeRandom() {
|
||||
if (size == 0)
|
||||
return null;
|
||||
|
||||
synchronized (this) {
|
||||
int random = randomEntryIndex();
|
||||
int index = findEntry(random, random % 2 == 0, false);
|
||||
if (index == -1)
|
||||
return null;
|
||||
Entry rem = table[index];
|
||||
table[index] = rem.next;
|
||||
size--;
|
||||
return rem;
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Find the index of the entry nearest the given index, starting in the
|
||||
* given direction.
|
||||
*/
|
||||
private int findEntry(int start, boolean forward, boolean searchedOther) {
|
||||
if (forward) {
|
||||
for (int i = start; i < table.length; i++)
|
||||
if (table[i] != null)
|
||||
return i;
|
||||
return (searchedOther || start == 0) ? -1
|
||||
: findEntry(start - 1, false, true);
|
||||
} else {
|
||||
for (int i = start; i >= 0; i--)
|
||||
if (table[i] != null)
|
||||
return i;
|
||||
return (searchedOther || start == table.length - 1) ? -1
|
||||
: findEntry(start + 1, true, true);
|
||||
}
|
||||
}
|
||||
|
||||
public Iterator randomEntryIterator() {
|
||||
// pass index so calculated before iterator refs table, in case table
|
||||
// gets replace with a larger one
|
||||
return new HashIterator(ENTRIES, randomEntryIndex());
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns <tt>true</tt> if this map maps one or more keys to the
|
||||
* specified value.
|
||||
*
|
||||
* @param value value whose presence in this map is to be tested.
|
||||
* @return <tt>true</tt> if this map maps one or more keys to the
|
||||
* specified value.
|
||||
*/
|
||||
public final boolean containsValue(Object value) {
|
||||
if (value == null) return containsNullValue();
|
||||
|
||||
Entry tab[] = table;
|
||||
for (int i = 0; i < tab.length; i++) {
|
||||
for (Entry e = tab[i]; e != null; e = e.next) {
|
||||
if (value.equals(e.value)) return true;
|
||||
}
|
||||
}
|
||||
return false;
|
||||
}
|
||||
|
||||
/**
|
||||
* Special-case code for containsValue with null argument
|
||||
*/
|
||||
private boolean containsNullValue() {
|
||||
Entry tab[] = table;
|
||||
for (int i = 0; i < tab.length; i++) {
|
||||
for (Entry e = tab[i]; e != null; e = e.next) {
|
||||
if (e.value == null) return true;
|
||||
}
|
||||
}
|
||||
return false;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a shallow copy of this <tt>ConcurrentHashMap</tt> instance: the
|
||||
* keys and values themselves are not cloned.
|
||||
*
|
||||
* @return a shallow copy of this map.
|
||||
*/
|
||||
public final Object clone() {
|
||||
return new ConcurrentHashMap(this);
|
||||
}
|
||||
|
||||
protected Entry createEntry(int h, Object k, Object v, Entry n) {
|
||||
return new Entry(h, k, v, n);
|
||||
}
|
||||
|
||||
protected static class Entry implements Map.Entry {
|
||||
|
||||
final Object key;
|
||||
Object value;
|
||||
final int hash;
|
||||
Entry next;
|
||||
|
||||
/**
|
||||
* Create new entry.
|
||||
*/
|
||||
protected Entry(int h, Object k, Object v, Entry n) {
|
||||
value = v;
|
||||
next = n;
|
||||
key = k;
|
||||
hash = h;
|
||||
}
|
||||
|
||||
public Object getKey() {
|
||||
return unmaskNull(key);
|
||||
}
|
||||
|
||||
public Object getValue() {
|
||||
return value;
|
||||
}
|
||||
|
||||
public Object setValue(Object newValue) {
|
||||
Object oldValue = value;
|
||||
value = newValue;
|
||||
return oldValue;
|
||||
}
|
||||
|
||||
public boolean equals(Object o) {
|
||||
if (!(o instanceof Map.Entry)) return false;
|
||||
Map.Entry e = (Map.Entry) o;
|
||||
Object k1 = getKey();
|
||||
Object k2 = e.getKey();
|
||||
if (k1 == k2 || (k1 != null && k1.equals(k2))) {
|
||||
Object v1 = getValue();
|
||||
Object v2 = e.getValue();
|
||||
if (v1 == v2 || (v1 != null && v1.equals(v2)))
|
||||
return true;
|
||||
}
|
||||
return false;
|
||||
}
|
||||
|
||||
public int hashCode() {
|
||||
return (key == NULL_KEY ? 0 : key.hashCode()) ^
|
||||
(value == null ? 0 : value.hashCode());
|
||||
}
|
||||
|
||||
public String toString() {
|
||||
return getKey() + "=" + getValue();
|
||||
}
|
||||
|
||||
protected Object clone() {
|
||||
// It is the callers responsibility to set the next field
|
||||
// correctly.
|
||||
return new Entry(hash, key, value, null);
|
||||
}
|
||||
}
|
||||
|
||||
// Types of Enumerations/Iterations
|
||||
private static final int KEYS = 0;
|
||||
private static final int VALUES = 1;
|
||||
private static final int ENTRIES = 2;
|
||||
|
||||
/**
|
||||
* Map iterator.
|
||||
*/
|
||||
private class HashIterator implements Iterator {
|
||||
|
||||
final Entry[] table = ConcurrentHashMap.this.table;
|
||||
final int type;
|
||||
int startIndex;
|
||||
int stopIndex = 0;
|
||||
int index;
|
||||
Entry entry = null;
|
||||
Entry lastReturned = null;
|
||||
|
||||
HashIterator(int type, int startIndex) {
|
||||
this.type = type;
|
||||
this.startIndex = startIndex;
|
||||
index = startIndex;
|
||||
}
|
||||
|
||||
public boolean hasNext() {
|
||||
if (entry != null) {
|
||||
return true;
|
||||
}
|
||||
while (index >= stopIndex) {
|
||||
if ((entry = table[index--]) != null) {
|
||||
return true;
|
||||
}
|
||||
}
|
||||
if (stopIndex == 0) {
|
||||
index = table.length - 1;
|
||||
stopIndex = startIndex + 1;
|
||||
while (index >= stopIndex) {
|
||||
if ((entry = table[index--]) != null) {
|
||||
return true;
|
||||
}
|
||||
}
|
||||
}
|
||||
return false;
|
||||
}
|
||||
|
||||
public Object next() {
|
||||
if (!hasNext())
|
||||
throw new NoSuchElementException();
|
||||
Entry e = lastReturned = entry;
|
||||
entry = e.next;
|
||||
return type == KEYS ? e.key : (type == VALUES ? e.value : e);
|
||||
}
|
||||
|
||||
public void remove() {
|
||||
if (lastReturned == null)
|
||||
throw new IllegalStateException();
|
||||
synchronized (ConcurrentHashMap.this) {
|
||||
Entry[] tab = ConcurrentHashMap.this.table;
|
||||
int index = (lastReturned.hash & 0x7FFFFFFF) % tab.length;
|
||||
|
||||
for (Entry e = tab[index], prev = null; e != null;
|
||||
prev = e, e = e.next) {
|
||||
if (e == lastReturned) {
|
||||
if (prev == null)
|
||||
tab[index] = e.next;
|
||||
else
|
||||
prev.next = e.next;
|
||||
size--;
|
||||
lastReturned = null;
|
||||
return;
|
||||
}
|
||||
}
|
||||
throw new Error("Iterated off table when doing remove");
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Views
|
||||
|
||||
private transient Set entrySet = null;
|
||||
private transient Set keySet = null;
|
||||
private transient Collection values = null;
|
||||
|
||||
/**
|
||||
* Returns a set view of the keys contained in this map. The set is
|
||||
* backed by the map, so changes to the map are reflected in the set, and
|
||||
* vice-versa. The set supports element removal, which removes the
|
||||
* corresponding mapping from this map, via the <tt>Iterator.remove</tt>,
|
||||
* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and
|
||||
* <tt>clear</tt> operations. It does not support the <tt>add</tt> or
|
||||
* <tt>addAll</tt> operations.
|
||||
*
|
||||
* @return a set view of the keys contained in this map.
|
||||
*/
|
||||
public final Set keySet() {
|
||||
Set ks = keySet;
|
||||
return (ks != null ? ks : (keySet = new KeySet()));
|
||||
}
|
||||
|
||||
private final class KeySet extends AbstractSet {
|
||||
|
||||
public Iterator iterator() {
|
||||
return new HashIterator(KEYS, table.length - 1);
|
||||
}
|
||||
|
||||
public int size() {
|
||||
return size;
|
||||
}
|
||||
|
||||
public boolean contains(Object o) {
|
||||
return containsKey(o);
|
||||
}
|
||||
|
||||
public boolean remove(Object o) {
|
||||
return ConcurrentHashMap.this.removeEntryForKey(o) != null;
|
||||
}
|
||||
|
||||
public void clear() {
|
||||
ConcurrentHashMap.this.clear();
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a collection view of the values contained in this map. The
|
||||
* collection is backed by the map, so changes to the map are reflected in
|
||||
* the collection, and vice-versa. The collection supports element
|
||||
* removal, which removes the corresponding mapping from this map, via the
|
||||
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
|
||||
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
|
||||
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
|
||||
*
|
||||
* @return a collection view of the values contained in this map.
|
||||
*/
|
||||
public final Collection values() {
|
||||
Collection vs = values;
|
||||
return (vs != null ? vs : (values = new Values()));
|
||||
}
|
||||
|
||||
private final class Values extends AbstractCollection {
|
||||
|
||||
public Iterator iterator() {
|
||||
return new HashIterator(VALUES, table.length - 1);
|
||||
}
|
||||
|
||||
public int size() {
|
||||
return size;
|
||||
}
|
||||
|
||||
public boolean contains(Object o) {
|
||||
return containsValue(o);
|
||||
}
|
||||
|
||||
public void clear() {
|
||||
ConcurrentHashMap.this.clear();
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a collection view of the mappings contained in this map. Each
|
||||
* element in the returned collection is a <tt>Map.Entry</tt>. The
|
||||
* collection is backed by the map, so changes to the map are reflected in
|
||||
* the collection, and vice-versa. The collection supports element
|
||||
* removal, which removes the corresponding mapping from the map, via the
|
||||
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
|
||||
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
|
||||
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
|
||||
*
|
||||
* @return a collection view of the mappings contained in this map.
|
||||
* @see Map.Entry
|
||||
*/
|
||||
public final Set entrySet() {
|
||||
Set es = entrySet;
|
||||
return (es != null ? es : (entrySet = new EntrySet()));
|
||||
}
|
||||
|
||||
private final class EntrySet extends AbstractSet {
|
||||
|
||||
public Iterator iterator() {
|
||||
return new HashIterator(ENTRIES, table.length - 1);
|
||||
}
|
||||
|
||||
public boolean contains(Object o) {
|
||||
if (!(o instanceof Map.Entry)) return false;
|
||||
Map.Entry e = (Map.Entry) o;
|
||||
Entry candidate = getEntry(e.getKey());
|
||||
return candidate != null && candidate.equals(e);
|
||||
}
|
||||
|
||||
public boolean remove(Object o) {
|
||||
return removeMapping(o) != null;
|
||||
}
|
||||
|
||||
public int size() {
|
||||
return size;
|
||||
}
|
||||
|
||||
public void clear() {
|
||||
ConcurrentHashMap.this.clear();
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Save the state of the <tt>ConcurrentHashMap</tt> instance to a stream
|
||||
* (i.e., serialize it).
|
||||
*
|
||||
* @serialData The <i>capacity</i> of the ConcurrentHashMap(the length of
|
||||
* the bucket array) is emitted(int), followed by the <i>size</i> of the
|
||||
* ConcurrentHashMap(the number of key-value mappings), followed by the key
|
||||
* (Object) and value(Object) for each key-value mapping represented by the
|
||||
* ConcurrentHashMap The key-value mappings are emitted in the order that
|
||||
* they are returned by <tt>entrySet().iterator()</tt>.
|
||||
*/
|
||||
private void writeObject(ObjectOutputStream s) throws IOException {
|
||||
// Write out the threshold, loadfactor, and any hidden stuff
|
||||
s.defaultWriteObject();
|
||||
|
||||
// Write out number of buckets
|
||||
s.writeInt(table.length);
|
||||
|
||||
// Write out size(number of Mappings)
|
||||
s.writeInt(size);
|
||||
s.writeInt(maxSize);
|
||||
|
||||
// Write out keys and values(alternating)
|
||||
for (Iterator i = entrySet().iterator(); i.hasNext();) {
|
||||
Map.Entry e = (Map.Entry) i.next();
|
||||
s.writeObject(e.getKey());
|
||||
s.writeObject(e.getValue());
|
||||
}
|
||||
}
|
||||
|
||||
private static final long serialVersionUID = -6452706556724125778L;
|
||||
|
||||
/**
|
||||
* Reconstitute the <tt>ConcurrentHashMap</tt> instance from a stream(i.e.,
|
||||
* deserialize it).
|
||||
*/
|
||||
private void readObject(ObjectInputStream s)
|
||||
throws IOException, ClassNotFoundException {
|
||||
// Read in the threshold, loadfactor, and any hidden stuff
|
||||
s.defaultReadObject();
|
||||
|
||||
// Read in number of buckets and allocate the bucket array;
|
||||
int numBuckets = s.readInt();
|
||||
table = new Entry[numBuckets];
|
||||
|
||||
// Read in size(number of Mappings)
|
||||
int size = s.readInt();
|
||||
|
||||
// read the max size
|
||||
maxSize = s.readInt();
|
||||
|
||||
// Read the keys and values, and put the mappings in the
|
||||
// ConcurrentHashMap
|
||||
for (int i = 0; i < size; i++) {
|
||||
Object key = s.readObject();
|
||||
Object value = s.readObject();
|
||||
put(key, value);
|
||||
}
|
||||
}
|
||||
}
|
||||
Loading…
Reference in New Issue