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java.lang.Objectjava.util.AbstractMap
org.apache.commons.collections.map.AbstractHashedMap
org.apache.commons.collections.map.AbstractReferenceMap
org.apache.commons.collections.map.ReferenceIdentityMap
public class ReferenceIdentityMap
A 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 Form| 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 |
| Nested classes/interfaces inherited from interface java.util.Map |
|---|
java.util.Map.Entry |
| Field Summary |
|---|
| Fields inherited from class org.apache.commons.collections.map.AbstractReferenceMap |
|---|
HARD, keyType, purgeValues, SOFT, valueType, WEAK |
| Fields inherited from class org.apache.commons.collections.map.AbstractHashedMap |
|---|
data, 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 Summary | |
|---|---|
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. |
|
| Method Summary | |
|---|---|
protected int |
hash(java.lang.Object key)
Gets the hash code for the key specified. |
protected int |
hashEntry(java.lang.Object key,
java.lang.Object value)
Gets the hash code for a MapEntry. |
protected boolean |
isEqualKey(java.lang.Object key1,
java.lang.Object key2)
Compares two keys for equals. |
protected boolean |
isEqualValue(java.lang.Object value1,
java.lang.Object value2)
Compares two values for equals. |
| Methods inherited from class org.apache.commons.collections.map.AbstractReferenceMap |
|---|
clear, containsKey, containsValue, createEntry, createEntrySetIterator, createKeySetIterator, createValuesIterator, doReadObject, doWriteObject, entrySet, get, getEntry, init, isEmpty, 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, clone, convertKey, destroyEntry, ensureCapacity, entryHashCode, entryKey, entryNext, entryValue, equals, hashCode, hashIndex, putAll, removeEntry, removeMapping, reuseEntry, toString, updateEntry |
| Methods inherited from class java.lang.Object |
|---|
finalize, getClass, notify, notifyAll, wait, wait, wait |
| Constructor Detail |
|---|
public 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.WEAK
public 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 collected
public 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 map
public 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 collected| Method Detail |
|---|
protected int hash(java.lang.Object key)
This implementation uses the identity hash code.
hash in class AbstractHashedMapkey - the key to get a hash code for
protected int hashEntry(java.lang.Object key,
java.lang.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 null
protected boolean isEqualKey(java.lang.Object key1,
java.lang.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.key
protected boolean isEqualValue(java.lang.Object value1,
java.lang.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()
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