Class ReferenceIdentityMap<K,V>
- Type Parameters:
K- the type of the keys in this mapV- the type of the values in this map
- All Implemented Interfaces:
Serializable,Map<K,,V> Get<K,,V> IterableGet<K,,V> IterableMap<K,,V> Put<K,V>
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<K, V>) to
provide synchronized access to a ReferenceIdentityMap.
Remember that synchronization will not stop the garbage collector 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<K, V>). This class may throw
exceptions when accessed by concurrent threads without synchronization.
- Since:
- 3.0 (previously in main package v2.1)
- See Also:
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Nested Class Summary
Nested classes/interfaces inherited from class org.apache.commons.collections4.map.AbstractReferenceMap
AbstractReferenceMap.ReferenceEntry<K,V>, AbstractReferenceMap.ReferenceStrength Nested classes/interfaces inherited from class org.apache.commons.collections4.map.AbstractHashedMap
AbstractHashedMap.EntrySet<K,V>, AbstractHashedMap.EntrySetIterator<K, V>, AbstractHashedMap.HashEntry<K, V>, AbstractHashedMap.HashIterator<K, V>, AbstractHashedMap.HashMapIterator<K, V>, AbstractHashedMap.KeySet<K>, AbstractHashedMap.KeySetIterator<K>, AbstractHashedMap.Values<V>, AbstractHashedMap.ValuesIterator<V> Nested classes/interfaces inherited from class java.util.AbstractMap
AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K, V> -
Field Summary
Fields inherited from class org.apache.commons.collections4.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 -
Constructor Summary
ConstructorsConstructorDescriptionConstructs a newReferenceIdentityMapthat will use hard references to keys and soft references to values.ReferenceIdentityMap(AbstractReferenceMap.ReferenceStrength keyType, AbstractReferenceMap.ReferenceStrength valueType) Constructs a newReferenceIdentityMapthat will use the specified types of references.ReferenceIdentityMap(AbstractReferenceMap.ReferenceStrength keyType, AbstractReferenceMap.ReferenceStrength valueType, boolean purgeValues) Constructs a newReferenceIdentityMapthat will use the specified types of references.ReferenceIdentityMap(AbstractReferenceMap.ReferenceStrength keyType, AbstractReferenceMap.ReferenceStrength valueType, int capacity, float loadFactor) Constructs a newReferenceIdentityMapwith the specified reference types, load factor and initial capacity.ReferenceIdentityMap(AbstractReferenceMap.ReferenceStrength keyType, AbstractReferenceMap.ReferenceStrength valueType, int capacity, float loadFactor, boolean purgeValues) Constructs a newReferenceIdentityMapwith the specified reference types, load factor and initial capacity. -
Method Summary
Modifier and TypeMethodDescriptionprotected intGets the hash code for the key specified.protected intGets the hash code for a MapEntry.protected booleanisEqualKey(Object key1, Object key2) Compares two keys for equals.protected booleanisEqualValue(Object value1, Object value2) Compares two values for equals.Methods inherited from class org.apache.commons.collections4.map.AbstractReferenceMap
clear, containsKey, containsValue, createEntry, createEntrySetIterator, createKeySetIterator, createValuesIterator, doReadObject, doWriteObject, entrySet, get, getEntry, init, isEmpty, isKeyType, isValueType, keySet, mapIterator, purge, purge, purgeBeforeRead, purgeBeforeWrite, put, remove, size, valuesMethods inherited from class org.apache.commons.collections4.map.AbstractHashedMap
addEntry, addMapping, calculateNewCapacity, calculateThreshold, checkCapacity, clone, convertKey, destroyEntry, ensureCapacity, entryHashCode, entryKey, entryNext, entryValue, equals, hashCode, hashIndex, putAll, removeEntry, removeMapping, reuseEntry, toString, updateEntryMethods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, waitMethods inherited from interface java.util.Map
compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll
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Constructor Details
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ReferenceIdentityMap
public ReferenceIdentityMap()Constructs a newReferenceIdentityMapthat will use hard references to keys and soft references to values. -
ReferenceIdentityMap
public ReferenceIdentityMap(AbstractReferenceMap.ReferenceStrength keyType, AbstractReferenceMap.ReferenceStrength valueType) Constructs a newReferenceIdentityMapthat will use the specified types of references. -
ReferenceIdentityMap
public ReferenceIdentityMap(AbstractReferenceMap.ReferenceStrength keyType, AbstractReferenceMap.ReferenceStrength valueType, boolean purgeValues) Constructs a newReferenceIdentityMapthat will use the specified types of references. -
ReferenceIdentityMap
public ReferenceIdentityMap(AbstractReferenceMap.ReferenceStrength keyType, AbstractReferenceMap.ReferenceStrength valueType, int capacity, float loadFactor) Constructs a newReferenceIdentityMapwith the specified reference types, load factor and initial capacity. -
ReferenceIdentityMap
public ReferenceIdentityMap(AbstractReferenceMap.ReferenceStrength keyType, AbstractReferenceMap.ReferenceStrength valueType, int capacity, float loadFactor, boolean purgeValues) Constructs a newReferenceIdentityMapwith the specified reference types, load factor and initial capacity.- Parameters:
keyType- the type of reference to use for keys; must beHARD,SOFT,WEAKvalueType- the type of reference to use for values; must beHARD,SOFT,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
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Method Details
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hash
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hashEntry
Gets the hash code for a MapEntry.This implementation uses the identity hash code.
- Overrides:
hashEntryin classAbstractReferenceMap<K,V> - 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
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isEqualKey
Compares two keys for equals.This implementation converts the key from the entry to a real reference before comparison and uses
==.- Overrides:
isEqualKeyin classAbstractReferenceMap<K,V> - 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
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isEqualValue
Compares two values for equals.This implementation uses
==.- Overrides:
isEqualValuein classAbstractHashedMap<K,V> - 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
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