public class ReferenceIdentityMap extends AbstractReferenceMap implements Serializable
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 Collections.synchronizedMap(java.util.Map) 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().
Note that ReferenceIdentityMap 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). This class may throw
exceptions when accessed by concurrent threads without synchronization.
Reference,
Serialized FormAbstractReferenceMap.ReferenceEntryAbstractHashedMap.EntrySet, AbstractHashedMap.EntrySetIterator, AbstractHashedMap.HashEntry, AbstractHashedMap.HashIterator, AbstractHashedMap.HashMapIterator, AbstractHashedMap.KeySet, AbstractHashedMap.KeySetIterator, AbstractHashedMap.Values, AbstractHashedMap.ValuesIteratorAbstractMap.SimpleEntry, AbstractMap.SimpleImmutableEntryHARD, keyType, purgeValues, SOFT, valueType, WEAKdata, DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD, entrySet, GETKEY_INVALID, GETVALUE_INVALID, keySet, loadFactor, MAXIMUM_CAPACITY, modCount, NO_NEXT_ENTRY, NO_PREVIOUS_ENTRY, NULL, REMOVE_INVALID, SETVALUE_INVALID, size, threshold, values| Constructor and Description |
|---|
ReferenceIdentityMap()
Constructs a new
ReferenceIdentityMap that will
use hard references to keys and soft references to values. |
ReferenceIdentityMap(int keyType,
int valueType)
Constructs a new
ReferenceIdentityMap that will
use the specified types of references. |
ReferenceIdentityMap(int keyType,
int valueType,
boolean purgeValues)
Constructs a new
ReferenceIdentityMap that will
use the specified types of references. |
ReferenceIdentityMap(int keyType,
int valueType,
int capacity,
float loadFactor)
Constructs a new
ReferenceIdentityMap with the
specified reference types, load factor and initial capacity. |
ReferenceIdentityMap(int keyType,
int valueType,
int capacity,
float loadFactor,
boolean purgeValues)
Constructs a new
ReferenceIdentityMap with the
specified reference types, load factor and initial capacity. |
| Modifier and Type | Method and Description |
|---|---|
protected int |
hash(Object key)
Gets the hash code for the key specified.
|
protected int |
hashEntry(Object key,
Object value)
Gets the hash code for a MapEntry.
|
protected boolean |
isEqualKey(Object key1,
Object key2)
Compares two keys for equals.
|
protected boolean |
isEqualValue(Object value1,
Object value2)
Compares two values for equals.
|
clear, containsKey, containsValue, createEntry, createEntrySetIterator, createKeySetIterator, createValuesIterator, doReadObject, doWriteObject, entrySet, get, getEntry, init, isEmpty, keySet, mapIterator, purge, purge, purgeBeforeRead, purgeBeforeWrite, put, remove, size, valuesaddEntry, addMapping, calculateNewCapacity, calculateThreshold, checkCapacity, clone, convertKey, destroyEntry, ensureCapacity, entryHashCode, entryKey, entryNext, entryValue, equals, hashCode, hashIndex, putAll, removeEntry, removeMapping, reuseEntry, toString, updateEntrypublic ReferenceIdentityMap()
ReferenceIdentityMap that will
use hard references to keys and soft references to values.public ReferenceIdentityMap(int keyType,
int valueType)
ReferenceIdentityMap 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 ReferenceIdentityMap(int keyType,
int valueType,
boolean purgeValues)
ReferenceIdentityMap 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 ReferenceIdentityMap(int keyType,
int valueType,
int capacity,
float loadFactor)
ReferenceIdentityMap 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 ReferenceIdentityMap(int keyType,
int valueType,
int capacity,
float loadFactor,
boolean purgeValues)
ReferenceIdentityMap 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 collectedprotected int hash(Object key)
This implementation uses the identity hash code.
hash in class AbstractHashedMapkey - the key to get a hash code forprotected int hashEntry(Object key, Object value)
This implementation uses the identity hash code.
hashEntry in class AbstractReferenceMapkey - the key to get a hash code for, may be nullvalue - the value to get a hash code for, may be nullprotected boolean isEqualKey(Object key1, Object key2)
This implementation converts the key from the entry to a real reference
before comparison and uses ==.
isEqualKey in class AbstractReferenceMapkey1 - the first key to compare passed in from outsidekey2 - the second key extracted from the entry via entry.keyprotected boolean isEqualValue(Object value1, Object value2)
This implementation uses ==.
isEqualValue in class AbstractHashedMapvalue1 - the first value to compare passed in from outsidevalue2 - the second value extracted from the entry via getValue()Copyright © 2001–2015 The Apache Software Foundation. All rights reserved.