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AbstractMap
org.apache.commons.collections.map.AbstractHashedMap
org.apache.commons.collections.map.AbstractReferenceMap
org.apache.commons.collections.map.ReferenceIdentityMap
Map
implementation that allows mappings to be
removed by the garbage collector and matches keys and values based
on ==
not equals()
.
When you construct a ReferenceIdentityMap
, you can specify what kind
of references are used to store the map's keys and values.
If non-hard references are used, then the garbage collector can remove
mappings if a key or value becomes unreachable, or if the JVM's memory is
running low. For information on how the different reference types behave,
see Reference
.
Different types of references can be specified for keys and values.
The default constructor uses hard keys and soft values, providing a
memory-sensitive cache.
This map is similar to
ReferenceMap
.
It differs in that keys and values in this class are compared using ==
.
This map will violate the detail of various Map and map view contracts.
As a general rule, don't compare this map to other maps.
This Map
implementation does not allow null elements.
Attempting to add a null key or value to the map will raise a NullPointerException
.
This implementation is not synchronized.
You can use java.util.Collections.synchronizedMap
to
provide synchronized access to a ReferenceIdentityMap
.
Remember that synchronization will not stop the garbage collecter removing entries.
All the available iterators can be reset back to the start by casting to
ResettableIterator
and calling reset()
.
java.lang.ref.Reference
Nested Class Summary |
Nested classes/interfaces inherited from class org.apache.commons.collections.map.AbstractReferenceMap | |
AbstractReferenceMap.ReferenceEntry |
Nested classes/interfaces inherited from class org.apache.commons.collections.map.AbstractHashedMap | |
AbstractHashedMap.EntrySet , AbstractHashedMap.EntrySetIterator , AbstractHashedMap.HashEntry , AbstractHashedMap.HashIterator , AbstractHashedMap.HashMapIterator , AbstractHashedMap.KeySet , AbstractHashedMap.KeySetIterator , AbstractHashedMap.Values , AbstractHashedMap.ValuesIterator |
Field Summary |
Fields inherited from class org.apache.commons.collections.map.AbstractReferenceMap | |
HARD , SOFT , WEAK , keyType , purgeValues , valueType |
Fields inherited from class org.apache.commons.collections.map.AbstractHashedMap | |
DEFAULT_CAPACITY , DEFAULT_LOAD_FACTOR , DEFAULT_THRESHOLD , GETKEY_INVALID , GETVALUE_INVALID , MAXIMUM_CAPACITY , NO_NEXT_ENTRY , NO_PREVIOUS_ENTRY , NULL , REMOVE_INVALID , SETVALUE_INVALID , data , entrySet , keySet , loadFactor , modCount , size , threshold , values |
Constructor Summary | |
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Method Summary | |
protected int |
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protected int |
|
protected boolean |
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protected boolean |
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Methods inherited from class org.apache.commons.collections.map.AbstractReferenceMap | |
clear , containsKey , containsValue , createEntry , createEntrySetIterator , createKeySetIterator , createValuesIterator , doReadObject , doWriteObject , entrySet , get , getEntry , hashEntry , init , isEmpty , isEqualKey , keySet , mapIterator , purge , purge , purgeBeforeRead , purgeBeforeWrite , put , remove , size , values |
Methods inherited from class org.apache.commons.collections.map.AbstractHashedMap | |
addEntry , addMapping , calculateNewCapacity , calculateThreshold , checkCapacity , clear , clone , containsKey , containsValue , convertKey , createEntry , createEntrySetIterator , createKeySetIterator , createValuesIterator , destroyEntry , doReadObject , doWriteObject , ensureCapacity , entryHashCode , entryKey , entryNext , entrySet , entryValue , equals , get , getEntry , hash , hashCode , hashIndex , init , isEmpty , isEqualKey , isEqualValue , keySet , mapIterator , put , putAll , remove , removeEntry , removeMapping , reuseEntry , size , toString , updateEntry , values |
public ReferenceIdentityMap()
Constructs a newReferenceIdentityMap
that will use hard references to keys and soft references to values.
public ReferenceIdentityMap(int keyType, int valueType)
Constructs a newReferenceIdentityMap
that will use the specified types of references.
- Parameters:
keyType
- the type of reference to use for keys; must beAbstractReferenceMap.HARD
,AbstractReferenceMap.SOFT
,AbstractReferenceMap.WEAK
valueType
- the type of reference to use for values; must beAbstractReferenceMap.HARD
,AbstractReferenceMap.SOFT
,AbstractReferenceMap.WEAK
public ReferenceIdentityMap(int keyType, int valueType, boolean purgeValues)
Constructs a newReferenceIdentityMap
that will use the specified types of references.
- Parameters:
keyType
- the type of reference to use for keys; must beAbstractReferenceMap.HARD
,AbstractReferenceMap.SOFT
,AbstractReferenceMap.WEAK
valueType
- the type of reference to use for values; must beAbstractReferenceMap.HARD
,AbstractReferenceMap.SOFT
,AbstractReferenceMap.WEAK
purgeValues
- should the value be automatically purged when the key is garbage collected
public ReferenceIdentityMap(int keyType, int valueType, int capacity, float loadFactor)
Constructs a newReferenceIdentityMap
with the specified reference types, load factor and initial capacity.
- Parameters:
keyType
- the type of reference to use for keys; must beAbstractReferenceMap.HARD
,AbstractReferenceMap.SOFT
,AbstractReferenceMap.WEAK
valueType
- the type of reference to use for values; must beAbstractReferenceMap.HARD
,AbstractReferenceMap.SOFT
,AbstractReferenceMap.WEAK
capacity
- the initial capacity for the maploadFactor
- the load factor for the map
public ReferenceIdentityMap(int keyType, int valueType, int capacity, float loadFactor, boolean purgeValues)
Constructs a newReferenceIdentityMap
with the specified reference types, load factor and initial capacity.
- Parameters:
keyType
- the type of reference to use for keys; must beAbstractReferenceMap.HARD
,AbstractReferenceMap.SOFT
,AbstractReferenceMap.WEAK
valueType
- the type of reference to use for values; must beAbstractReferenceMap.HARD
,AbstractReferenceMap.SOFT
,AbstractReferenceMap.WEAK
capacity
- the initial capacity for the maploadFactor
- the load factor for the mappurgeValues
- should the value be automatically purged when the key is garbage collected
protected int hash(Object key)
Gets the hash code for the key specified. This implementation uses the identity hash code.
- Overrides:
- hash in interface AbstractHashedMap
- Parameters:
key
- the key to get a hash code for
- Returns:
- the hash code
protected int hashEntry(Object key, Object value)
Gets the hash code for a MapEntry. This implementation uses the identity hash code.
- Overrides:
- hashEntry in interface AbstractReferenceMap
- Parameters:
key
- the key to get a hash code for, may be nullvalue
- the value to get a hash code for, may be null
- Returns:
- the hash code, as per the MapEntry specification
protected boolean isEqualKey(Object key1, Object key2)
Compares two keys for equals. This implementation converts the key from the entry to a real reference before comparison and uses==
.
- Overrides:
- isEqualKey in interface AbstractReferenceMap
- Parameters:
key1
- the first key to compare passed in from outsidekey2
- the second key extracted from the entry viaentry.key
- Returns:
- true if equal by identity
protected boolean isEqualValue(Object value1, Object value2)
Compares two values for equals. This implementation uses==
.
- Overrides:
- isEqualValue in interface AbstractHashedMap
- Parameters:
value1
- the first value to compare passed in from outsidevalue2
- the second value extracted from the entry viagetValue()
- Returns:
- true if equal by identity