java.lang.Object
- java.util.AbstractMap<K,V>
- - org.springframework.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 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, Juergen Hoeller

嵌套类概要

嵌套类
修饰符和类型	类	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 `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 extends Object,V extends Object>, AbstractMap.SimpleImmutableEntry<K extends Object,V extends Object>

构造器概要

构造器
构造器	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.
`ConcurrentReferenceHashMap(int initialCapacity, ConcurrentReferenceHashMap.ReferenceType referenceType)`	Create a new `ConcurrentReferenceHashMap` instance.

方法概要

所有方法静态方法实例方法具体方法
修饰符和类型	方法	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()`
`V`	`getOrDefault(Object key, V defaultValue)`
`protected ConcurrentReferenceHashMap.Reference<K,V>`	`getReference(Object key, ConcurrentReferenceHashMap.Restructure restructure)`	Return 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()`
`boolean`	`isEmpty()`
`void`	`purgeUnreferencedEntries()`	Remove any entries that have been garbage collected and are no longer referenced.
`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, 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.concurrent.ConcurrentMap
compute, computeIfAbsent, computeIfPresent, forEach, merge, replaceAll

从接口继承的方法 java.util.Map
containsValue, equals, hashCode, 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,
                                  ConcurrentReferenceHashMap.ReferenceType referenceType)
```
    Create a new ConcurrentReferenceHashMap instance.
    参数:
    initialCapacity - the initial capacity of the map
    referenceType - the reference type used for entries (soft or weak)
  - 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 (soft or weak)
- 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(@Nullable
                      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
```
@Nullable
public V get(@Nullable
             Object key)
```
    指定者:
    get 在接口中 Map<K,V>
    覆盖:
    get 在类中 AbstractMap<K,V>
  - getOrDefault
```
@Nullable
public V getOrDefault(@Nullable
                      Object key,
                      @Nullable
                      V defaultValue)
```
    指定者:
    getOrDefault 在接口中 ConcurrentMap<K,V>
    指定者:
    getOrDefault 在接口中 Map<K,V>
  - containsKey
```
public boolean containsKey(@Nullable
                           Object key)
```
    指定者:
    containsKey 在接口中 Map<K,V>
    覆盖:
    containsKey 在类中 AbstractMap<K,V>
  - getReference
```
@Nullable
protected final ConcurrentReferenceHashMap.Reference<K,V> getReference(@Nullable
                                                                             Object key,
                                                                             ConcurrentReferenceHashMap.Restructure restructure)
```
    Return 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 if not found
  - put
```
@Nullable
public V put(@Nullable
             K key,
             @Nullable
             V value)
```
    指定者:
    put 在接口中 Map<K,V>
    覆盖:
    put 在类中 AbstractMap<K,V>
  - putIfAbsent
```
@Nullable
public V putIfAbsent(@Nullable
                     K key,
                     @Nullable
                     V value)
```
    指定者:
    putIfAbsent 在接口中 ConcurrentMap<K,V>
    指定者:
    putIfAbsent 在接口中 Map<K,V>
  - remove
```
@Nullable
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>
    指定者:
    remove 在接口中 Map<K,V>
  - replace
```
public boolean replace(K key,
                       V oldValue,
                       V newValue)
```
    指定者:
    replace 在接口中 ConcurrentMap<K,V>
    指定者:
    replace 在接口中 Map<K,V>
  - replace
```
@Nullable
public V replace(K key,
                 V value)
```
    指定者:
    replace 在接口中 ConcurrentMap<K,V>
    指定者:
    replace 在接口中 Map<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>
  - purgeUnreferencedEntries
```
public void purgeUnreferencedEntries()
```
    Remove any entries that have been garbage collected and are no longer referenced. Under normal circumstances garbage collected entries are automatically purged as items are added or removed from the Map. This method can be used to force a purge, and is useful when the Map is read frequently but updated less often.
  - size
```
public int size()
```
    指定者:
    size 在接口中 Map<K,V>
    覆盖:
    size 在类中 AbstractMap<K,V>
  - isEmpty
```
public boolean isEmpty()
```
    指定者:
    isEmpty 在接口中 Map<K,V>
    覆盖:
    isEmpty 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)

类 ConcurrentReferenceHashMap<K,​V>

嵌套类概要

从类继承的嵌套类/接口 java.util.AbstractMap

构造器概要

方法概要

从类继承的方法 java.util.AbstractMap

从类继承的方法 java.lang.Object

从接口继承的方法 java.util.concurrent.ConcurrentMap

从接口继承的方法 java.util.Map

构造器详细资料

ConcurrentReferenceHashMap

ConcurrentReferenceHashMap

ConcurrentReferenceHashMap

ConcurrentReferenceHashMap

ConcurrentReferenceHashMap

ConcurrentReferenceHashMap

ConcurrentReferenceHashMap

方法详细资料

getLoadFactor

getSegmentsSize

getSegment

createReferenceManager

getHash

get

getOrDefault

containsKey

getReference

put

putIfAbsent

remove

remove

replace

replace

clear

purgeUnreferencedEntries

size

isEmpty

entrySet

calculateShift

类 ConcurrentReferenceHashMap<K,V>