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AbstractMap
org.apache.commons.collections.map.AbstractHashedMap
org.apache.commons.collections.map.AbstractReferenceMap
org.apache.commons.collections.map.ReferenceMap
Map
implementation that allows mappings to be
removed by the garbage collector.
When you construct a ReferenceMap
, 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 keys can be configured to be weak but the values hard,
in which case this class will behave like a
WeakHashMap
. However, you can also specify hard keys and
weak values, or any other combination. The default constructor uses
hard keys and soft values, providing a memory-sensitive cache.
This map is similar to
ReferenceIdentityMap
.
It differs in that keys and values in this class are compared using equals()
.
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 ReferenceMap
.
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()
.
NOTE: As from Commons Collections 3.1 this map extends AbstractReferenceMap
(previously it extended AbstractMap). As a result, the implementation is now
extensible and provides a MapIterator
.
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 |
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 ReferenceMap()
Constructs a newReferenceMap
that will use hard references to keys and soft references to values.
public ReferenceMap(int keyType, int valueType)
Constructs a newReferenceMap
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 ReferenceMap(int keyType, int valueType, boolean purgeValues)
Constructs a newReferenceMap
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 ReferenceMap(int keyType, int valueType, int capacity, float loadFactor)
Constructs a newReferenceMap
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 ReferenceMap(int keyType, int valueType, int capacity, float loadFactor, boolean purgeValues)
Constructs a newReferenceMap
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