org.skfiy.util

类 ConcurrentReferenceHashMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

org.skfiy.util.ConcurrentReferenceHashMap<K,V>

类型参数:

K - The key type

V - The value type

所有已实现的接口:

ConcurrentMap<K,V>, Map<K,V>

public class ConcurrentReferenceHashMap<K,V>
extends AbstractMap<K,V>
implements ConcurrentMap<K,V>

A ConcurrentHashMap that uses soft or weak references for both keys and values.

This class can be used as an alternative to null Collections.synchronizedMap(new WeakHashMap<K, Reference<V>>()) in order to support better performance when accessed concurrently. This implementation follows the same design constraints as ConcurrentHashMap with the exception that null values and null keys are supported.

NOTE: The use of references means that there is no guarantee that items placed into the map will be subsequently available. The garbage collector may discard references at any time, so it may appear that an unknown thread is silently removing entries.

If not explicitly specified this implementation will use soft entry references.

从以下版本开始:

3.2

作者:

Phillip Webb

嵌套类概要

嵌套类

限定符和类型	类和说明
protected static class	ConcurrentReferenceHashMap.Entry<K,V> A single map entry.
protected static interface	ConcurrentReferenceHashMap.Reference<K,V> A reference to an ConcurrentReferenceHashMap.Entry contained in the map.
protected class	ConcurrentReferenceHashMap.ReferenceManager Strategy class used to manage ConcurrentReferenceHashMap.References.
static class	ConcurrentReferenceHashMap.ReferenceType Various reference types supported by this map.
protected static class	ConcurrentReferenceHashMap.Restructure The types of restructuring that can be performed.
protected class	ConcurrentReferenceHashMap.Segment A single segment used to divide the map to allow better concurrent performance.

从类继承的嵌套类/接口 java.util.AbstractMap

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

构造器概要

构造器

构造器和说明
ConcurrentReferenceHashMap() Create a new ConcurrentReferenceHashMap instance.
ConcurrentReferenceHashMap(int initialCapacity) Create a new ConcurrentReferenceHashMap instance.
ConcurrentReferenceHashMap(int initialCapacity, float loadFactor) Create a new ConcurrentReferenceHashMap instance.
ConcurrentReferenceHashMap(int initialCapacity, float loadFactor, int concurrencyLevel) Create a new ConcurrentReferenceHashMap instance.
ConcurrentReferenceHashMap(int initialCapacity, float loadFactor, int concurrencyLevel, ConcurrentReferenceHashMap.ReferenceType referenceType) Create a new ConcurrentReferenceHashMap instance.
ConcurrentReferenceHashMap(int initialCapacity, int concurrencyLevel) Create a new ConcurrentReferenceHashMap instance.

方法概要

方法

限定符和类型	方法和说明
protected static int	calculateShift(int minimumValue, int maximumValue) Calculate a shift value that can be used to create a power-of-two value between the specified maximum and minimum values.
void	clear()
boolean	containsKey(Object key)
protected ConcurrentReferenceHashMap.ReferenceManager	createReferenceManager() Factory method that returns the ConcurrentReferenceHashMap.ReferenceManager.
Set<Map.Entry<K,V>>	entrySet()
V	get(Object key)
protected int	getHash(Object o) Get the hash for a given object, apply an additional hash function to reduce collisions.
protected float	getLoadFactor()
protected ConcurrentReferenceHashMap.Reference<K,V>	getReference(Object key, ConcurrentReferenceHashMap.Restructure restructure) Returns a ConcurrentReferenceHashMap.Reference to the ConcurrentReferenceHashMap.Entry for the specified key or null if not found.
protected ConcurrentReferenceHashMap.Segment	getSegment(int index)
protected int	getSegmentsSize()
V	put(K key, V value)
V	putIfAbsent(K key, V value)
V	remove(Object key)
boolean	remove(Object key, Object value)
V	replace(K key, V value)
boolean	replace(K key, V oldValue, V newValue)
int	size()

从类继承的方法 java.util.AbstractMap

clone, containsValue, equals, hashCode, isEmpty, keySet, putAll, toString, values

从类继承的方法 java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

从接口继承的方法 java.util.Map

containsValue, equals, hashCode, isEmpty, keySet, putAll, values

构造器详细资料

ConcurrentReferenceHashMap

public ConcurrentReferenceHashMap()

Create a new ConcurrentReferenceHashMap instance.

ConcurrentReferenceHashMap

public ConcurrentReferenceHashMap(int initialCapacity)

Create a new ConcurrentReferenceHashMap instance.

参数:

initialCapacity - the initial capacity of the map

ConcurrentReferenceHashMap

public ConcurrentReferenceHashMap(int initialCapacity,
                          float loadFactor)

Create a new ConcurrentReferenceHashMap instance.

参数:

initialCapacity - the initial capacity of the map

loadFactor - the load factor. When the average number of references per table exceeds this value resize will be attempted

ConcurrentReferenceHashMap

public ConcurrentReferenceHashMap(int initialCapacity,
                          int concurrencyLevel)

Create a new ConcurrentReferenceHashMap instance.

参数:

initialCapacity - the initial capacity of the map

concurrencyLevel - the expected number of threads that will concurrently write to the map

ConcurrentReferenceHashMap

public ConcurrentReferenceHashMap(int initialCapacity,
                          float loadFactor,
                          int concurrencyLevel)

Create a new ConcurrentReferenceHashMap instance.

参数:

initialCapacity - the initial capacity of the map

loadFactor - the load factor. When the average number of references per table exceeds this value resize will be attempted

concurrencyLevel - the expected number of threads that will concurrently write to the map

ConcurrentReferenceHashMap

public ConcurrentReferenceHashMap(int initialCapacity,
                          float loadFactor,
                          int concurrencyLevel,
                          ConcurrentReferenceHashMap.ReferenceType referenceType)

Create a new ConcurrentReferenceHashMap instance.

参数:

initialCapacity - the initial capacity of the map

loadFactor - the load factor. When the average number of references per table exceeds this value resize will be attempted

concurrencyLevel - the expected number of threads that will concurrently write to the map

referenceType - the reference type used for entries

方法详细资料

getLoadFactor

protected final float getLoadFactor()

getSegmentsSize

protected final int getSegmentsSize()

getSegment

protected final ConcurrentReferenceHashMap.Segment getSegment(int index)

createReferenceManager

protected ConcurrentReferenceHashMap.ReferenceManager createReferenceManager()

Factory method that returns the ConcurrentReferenceHashMap.ReferenceManager. This method will be called once for each ConcurrentReferenceHashMap.Segment.

返回:

a new reference manager

getHash

protected int getHash(Object o)

Get the hash for a given object, apply an additional hash function to reduce collisions. This implementation uses the same Wang/Jenkins algorithm as ConcurrentHashMap. Subclasses can override to provide alternative hashing.

参数:

o - the object to hash (may be null)

返回:

the resulting hash code

get

public V get(Object key)

指定者:

get 在接口中 Map<K,V>

覆盖:

get 在类中 AbstractMap<K,V>

containsKey

public boolean containsKey(Object key)

指定者:

containsKey 在接口中 Map<K,V>

覆盖:

containsKey 在类中 AbstractMap<K,V>

getReference

protected final ConcurrentReferenceHashMap.Reference<K,V> getReference(Object key,
                                                     ConcurrentReferenceHashMap.Restructure restructure)

Returns a ConcurrentReferenceHashMap.Reference to the ConcurrentReferenceHashMap.Entry for the specified key or null if not found.

参数:

key - the key (can be null)

restructure - types of restructure allowed during this call

返回:

the reference or null

put

public V put(K key,
    V value)

指定者:

put 在接口中 Map<K,V>

覆盖:

put 在类中 AbstractMap<K,V>

putIfAbsent

public V putIfAbsent(K key,
            V value)

指定者:

putIfAbsent 在接口中 ConcurrentMap<K,V>

remove

public V remove(Object key)

指定者:

remove 在接口中 Map<K,V>

覆盖:

remove 在类中 AbstractMap<K,V>

remove

public boolean remove(Object key,
             Object value)

指定者:

remove 在接口中 ConcurrentMap<K,V>

replace

public boolean replace(K key,
              V oldValue,
              V newValue)

指定者:

replace 在接口中 ConcurrentMap<K,V>

replace

public V replace(K key,
        V value)

指定者:

replace 在接口中 ConcurrentMap<K,V>

clear

public void clear()

指定者:

clear 在接口中 Map<K,V>

覆盖:

clear 在类中 AbstractMap<K,V>

size

public int size()

指定者:

size 在接口中 Map<K,V>

覆盖:

size 在类中 AbstractMap<K,V>

entrySet

public Set<Map.Entry<K,V>> entrySet()

指定者:

entrySet 在接口中 Map<K,V>

指定者:

entrySet 在类中 AbstractMap<K,V>

calculateShift

protected static int calculateShift(int minimumValue,
                 int maximumValue)

Calculate a shift value that can be used to create a power-of-two value between the specified maximum and minimum values.

参数:

minimumValue - the minimum value

maximumValue - the maximum value

返回:

the calculated shift (use 1 << shift to obtain a value)