public class ReferenceMap extends AbstractReferenceMap implements java.io.Serializable
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 Collections.synchronizedMap(java.util.Map<K, V>) 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 that ReferenceMap is not synchronized and is not thread-safe.
If you wish to use this map from multiple threads concurrently, you must use
appropriate synchronization. The simplest approach is to wrap this map
using Collections.synchronizedMap(java.util.Map<K, V>). This class may throw
exceptions when accessed by concurrent threads without synchronization.
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.
Reference,
Serialized FormHARD, SOFT, WEAK| Constructor and Description |
|---|
ReferenceMap()
Constructs a new
ReferenceMap that will
use hard references to keys and soft references to values. |
ReferenceMap(int keyType,
int valueType)
Constructs a new
ReferenceMap that will
use the specified types of references. |
ReferenceMap(int keyType,
int valueType,
boolean purgeValues)
Constructs a new
ReferenceMap that will
use the specified types of references. |
ReferenceMap(int keyType,
int valueType,
int capacity,
float loadFactor)
Constructs a new
ReferenceMap with the
specified reference types, load factor and initial
capacity. |
ReferenceMap(int keyType,
int valueType,
int capacity,
float loadFactor,
boolean purgeValues)
Constructs a new
ReferenceMap with the
specified reference types, load factor and initial
capacity. |
clear, containsKey, containsValue, entrySet, get, isEmpty, keySet, mapIterator, put, remove, size, valuesequals, hashCode, putAll, toStringpublic ReferenceMap()
ReferenceMap that will
use hard references to keys and soft references to values.public ReferenceMap(int keyType,
int valueType)
ReferenceMap that will
use the specified types of references.keyType - the type of reference to use for keys;
must be AbstractReferenceMap.HARD, AbstractReferenceMap.SOFT, AbstractReferenceMap.WEAKvalueType - the type of reference to use for values;
must be AbstractReferenceMap.HARD, AbstractReferenceMap.SOFT, AbstractReferenceMap.WEAKpublic ReferenceMap(int keyType,
int valueType,
boolean purgeValues)
ReferenceMap that will
use the specified types of references.keyType - the type of reference to use for keys;
must be AbstractReferenceMap.HARD, AbstractReferenceMap.SOFT, AbstractReferenceMap.WEAKvalueType - the type of reference to use for values;
must be AbstractReferenceMap.HARD, AbstractReferenceMap.SOFT, AbstractReferenceMap.WEAKpurgeValues - should the value be automatically purged when the
key is garbage collectedpublic ReferenceMap(int keyType,
int valueType,
int capacity,
float loadFactor)
ReferenceMap with the
specified reference types, load factor and initial
capacity.keyType - the type of reference to use for keys;
must be AbstractReferenceMap.HARD, AbstractReferenceMap.SOFT, AbstractReferenceMap.WEAKvalueType - the type of reference to use for values;
must be AbstractReferenceMap.HARD, AbstractReferenceMap.SOFT, AbstractReferenceMap.WEAKcapacity - the initial capacity for the maploadFactor - the load factor for the mappublic ReferenceMap(int keyType,
int valueType,
int capacity,
float loadFactor,
boolean purgeValues)
ReferenceMap with the
specified reference types, load factor and initial
capacity.keyType - the type of reference to use for keys;
must be AbstractReferenceMap.HARD, AbstractReferenceMap.SOFT, AbstractReferenceMap.WEAKvalueType - the type of reference to use for values;
must be AbstractReferenceMap.HARD, AbstractReferenceMap.SOFT, AbstractReferenceMap.WEAKcapacity - the initial capacity for the maploadFactor - the load factor for the mappurgeValues - should the value be automatically purged when the
key is garbage collectedCopyright © 2010 - 2020 Adobe. All Rights Reserved