Class ReferenceMap
- java.lang.Object
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- java.util.AbstractMap
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- org.apache.commons.collections.ReferenceMap
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- All Implemented Interfaces:
java.util.Map
public class ReferenceMap extends java.util.AbstractMap
Deprecated.Moved to map subpackage. Due to be removed in v4.0.Hash-basedMap
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, seeReference
.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.The algorithms used are basically the same as those in
HashMap
. In particular, you can specify a load factor and capacity to suit your needs. All optionalMap
operations are supported.However, this
Map
implementation does not allow null elements. Attempting to add a null key or or a null value to the map will raise aNullPointerException
.As usual, this implementation is not synchronized. You can use
Collections.synchronizedMap(java.util.Map<K, V>)
to provide synchronized access to aReferenceMap
.- Since:
- Commons Collections 2.1
- Version:
- $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
- See Also:
Reference
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Nested Class Summary
Nested Classes Modifier and Type Class Description private class
ReferenceMap.Entry
Deprecated.private class
ReferenceMap.EntryIterator
Deprecated.private class
ReferenceMap.KeyIterator
Deprecated.private static class
ReferenceMap.SoftRef
Deprecated.private class
ReferenceMap.ValueIterator
Deprecated.private static class
ReferenceMap.WeakRef
Deprecated.
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Field Summary
Fields Modifier and Type Field Description private java.util.Set
entrySet
Deprecated.Cached entry set.static int
HARD
Deprecated.Constant indicating that hard references should be used.private java.util.Set
keySet
Deprecated.Cached key set.private int
keyType
Deprecated.The reference type for keys.private float
loadFactor
Deprecated.The threshold variable is calculated by multiplying table.length and loadFactor.private int
modCount
Deprecated.Number of times this map has been modified.private boolean
purgeValues
Deprecated.Should the value be automatically purged when the associated key has been collected?private java.lang.ref.ReferenceQueue
queue
Deprecated.ReferenceQueue used to eliminate stale mappings.private static long
serialVersionUID
Deprecated.For serialization.private int
size
Deprecated.Number of mappings in this map.static int
SOFT
Deprecated.Constant indicating that soft references should be used.private ReferenceMap.Entry[]
table
Deprecated.The hash table.private int
threshold
Deprecated.When size reaches threshold, the map is resized.private java.util.Collection
values
Deprecated.Cached values.private int
valueType
Deprecated.The reference type for values.static int
WEAK
Deprecated.Constant indicating that weak references should be used.
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Constructor Summary
Constructors Constructor Description ReferenceMap()
Deprecated.Constructs a newReferenceMap
that will use hard references to keys and soft references to values.ReferenceMap(int keyType, int valueType)
Deprecated.Constructs a newReferenceMap
that will use the specified types of references.ReferenceMap(int keyType, int valueType, boolean purgeValues)
Deprecated.Constructs a newReferenceMap
that will use the specified types of references.ReferenceMap(int keyType, int valueType, int capacity, float loadFactor)
Deprecated.Constructs a newReferenceMap
with the specified reference types, load factor and initial capacity.ReferenceMap(int keyType, int valueType, int capacity, float loadFactor, boolean purgeValues)
Deprecated.Constructs a newReferenceMap
with the specified reference types, load factor and initial capacity.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description void
clear()
Deprecated.Clears this map.boolean
containsKey(java.lang.Object key)
Deprecated.Returnstrue
if this map contains the given key.java.util.Set
entrySet()
Deprecated.Returns a set view of this map's entries.java.lang.Object
get(java.lang.Object key)
Deprecated.Returns the value associated with the given key, if any.private ReferenceMap.Entry
getEntry(java.lang.Object key)
Deprecated.Returns the entry associated with the given key.private int
indexFor(int hash)
Deprecated.Converts the given hash code into an index into the hash table.boolean
isEmpty()
Deprecated.Returnstrue
if this map is empty.java.util.Set
keySet()
Deprecated.Returns a set view of this map's keys.private void
purge()
Deprecated.Purges stale mappings from this map.private void
purge(java.lang.ref.Reference ref)
Deprecated.java.lang.Object
put(java.lang.Object key, java.lang.Object value)
Deprecated.Associates the given key with the given value.private void
readObject(java.io.ObjectInputStream inp)
Deprecated.Reads the contents of this object from the given input stream.java.lang.Object
remove(java.lang.Object key)
Deprecated.Removes the key and its associated value from this map.private void
resize()
Deprecated.Resizes this hash table by doubling its capacity.int
size()
Deprecated.Returns the size of this map.private java.lang.Object
toReference(int type, java.lang.Object referent, int hash)
Deprecated.Constructs a reference of the given type to the given referent.java.util.Collection
values()
Deprecated.Returns a collection view of this map's values.private static void
verify(java.lang.String name, int type)
Deprecated.private void
writeObject(java.io.ObjectOutputStream out)
Deprecated.Writes this object to the given output stream.-
Methods inherited from class java.util.AbstractMap
clone, containsValue, equals, hashCode, putAll, toString
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Field Detail
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serialVersionUID
private static final long serialVersionUID
Deprecated.For serialization.- See Also:
- Constant Field Values
-
HARD
public static final int HARD
Deprecated.Constant indicating that hard references should be used.- See Also:
- Constant Field Values
-
SOFT
public static final int SOFT
Deprecated.Constant indicating that soft references should be used.- See Also:
- Constant Field Values
-
WEAK
public static final int WEAK
Deprecated.Constant indicating that weak references should be used.- See Also:
- Constant Field Values
-
keyType
private int keyType
Deprecated.The reference type for keys. Must be HARD, SOFT, WEAK. Note: I originally marked this field as final, but then this class didn't compile under JDK1.2.2.
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valueType
private int valueType
Deprecated.The reference type for values. Must be HARD, SOFT, WEAK. Note: I originally marked this field as final, but then this class didn't compile under JDK1.2.2.
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loadFactor
private float loadFactor
Deprecated.The threshold variable is calculated by multiplying table.length and loadFactor. Note: I originally marked this field as final, but then this class didn't compile under JDK1.2.2.
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purgeValues
private boolean purgeValues
Deprecated.Should the value be automatically purged when the associated key has been collected?
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queue
private transient java.lang.ref.ReferenceQueue queue
Deprecated.ReferenceQueue used to eliminate stale mappings. See purge.
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table
private transient ReferenceMap.Entry[] table
Deprecated.The hash table. Its length is always a power of two.
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size
private transient int size
Deprecated.Number of mappings in this map.
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threshold
private transient int threshold
Deprecated.When size reaches threshold, the map is resized. See resize().
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modCount
private transient volatile int modCount
Deprecated.Number of times this map has been modified.
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keySet
private transient java.util.Set keySet
Deprecated.Cached key set. May be null if key set is never accessed.
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entrySet
private transient java.util.Set entrySet
Deprecated.Cached entry set. May be null if entry set is never accessed.
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values
private transient java.util.Collection values
Deprecated.Cached values. May be null if values() is never accessed.
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Constructor Detail
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ReferenceMap
public ReferenceMap()
Deprecated.Constructs a newReferenceMap
that will use hard references to keys and soft references to values.
-
ReferenceMap
public ReferenceMap(int keyType, int valueType, boolean purgeValues)
Deprecated.Constructs a newReferenceMap
that will use the specified types of references.
-
ReferenceMap
public ReferenceMap(int keyType, int valueType)
Deprecated.Constructs a newReferenceMap
that will use the specified types of references.
-
ReferenceMap
public ReferenceMap(int keyType, int valueType, int capacity, float loadFactor, boolean purgeValues)
Deprecated.Constructs a newReferenceMap
with the specified reference types, load factor and initial capacity.- Parameters:
keyType
- the type of reference to use for keys; must beHARD
,SOFT
,WEAK
valueType
- the type of reference to use for values; must beHARD
,SOFT
,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
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ReferenceMap
public ReferenceMap(int keyType, int valueType, int capacity, float loadFactor)
Deprecated.Constructs a newReferenceMap
with the specified reference types, load factor and initial capacity.
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Method Detail
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verify
private static void verify(java.lang.String name, int type)
Deprecated.
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writeObject
private void writeObject(java.io.ObjectOutputStream out) throws java.io.IOException
Deprecated.Writes this object to the given output stream.- Parameters:
out
- the output stream to write to- Throws:
java.io.IOException
- if the stream raises it
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readObject
private void readObject(java.io.ObjectInputStream inp) throws java.io.IOException, java.lang.ClassNotFoundException
Deprecated.Reads the contents of this object from the given input stream.- Parameters:
inp
- the input stream to read from- Throws:
java.io.IOException
- if the stream raises itjava.lang.ClassNotFoundException
- if the stream raises it
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toReference
private java.lang.Object toReference(int type, java.lang.Object referent, int hash)
Deprecated.Constructs a reference of the given type to the given referent. The reference is registered with the queue for later purging.- Parameters:
type
- HARD, SOFT or WEAKreferent
- the object to refer tohash
- the hash code of the key of the mapping; this number might be different from referent.hashCode() if the referent represents a value and not a key
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getEntry
private ReferenceMap.Entry getEntry(java.lang.Object key)
Deprecated.Returns the entry associated with the given key.- Parameters:
key
- the key of the entry to look up- Returns:
- the entry associated with that key, or null if the key is not in this map
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indexFor
private int indexFor(int hash)
Deprecated.Converts the given hash code into an index into the hash table.
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resize
private void resize()
Deprecated.Resizes this hash table by doubling its capacity. This is an expensive operation, as entries must be copied from the old smaller table to the new bigger table.
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purge
private void purge()
Deprecated.Purges stale mappings from this map.Ordinarily, stale mappings are only removed during a write operation, although this method is called for both read and write operations to maintain a consistent state.
Note that this method is not synchronized! Special care must be taken if, for instance, you want stale mappings to be removed on a periodic basis by some background thread.
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purge
private void purge(java.lang.ref.Reference ref)
Deprecated.
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size
public int size()
Deprecated.Returns the size of this map.- Specified by:
size
in interfacejava.util.Map
- Overrides:
size
in classjava.util.AbstractMap
- Returns:
- the size of this map
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isEmpty
public boolean isEmpty()
Deprecated.Returnstrue
if this map is empty.- Specified by:
isEmpty
in interfacejava.util.Map
- Overrides:
isEmpty
in classjava.util.AbstractMap
- Returns:
true
if this map is empty
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containsKey
public boolean containsKey(java.lang.Object key)
Deprecated.Returnstrue
if this map contains the given key.- Specified by:
containsKey
in interfacejava.util.Map
- Overrides:
containsKey
in classjava.util.AbstractMap
- Returns:
- true if the given key is in this map
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get
public java.lang.Object get(java.lang.Object key)
Deprecated.Returns the value associated with the given key, if any.- Specified by:
get
in interfacejava.util.Map
- Overrides:
get
in classjava.util.AbstractMap
- Returns:
- the value associated with the given key, or
null
if the key maps to no value
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put
public java.lang.Object put(java.lang.Object key, java.lang.Object value)
Deprecated.Associates the given key with the given value.Neither the key nor the value may be null.
- Specified by:
put
in interfacejava.util.Map
- Overrides:
put
in classjava.util.AbstractMap
- Parameters:
key
- the key of the mappingvalue
- the value of the mapping- Returns:
- the last value associated with that key, or null if no value was associated with the key
- Throws:
java.lang.NullPointerException
- if either the key or value is null
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remove
public java.lang.Object remove(java.lang.Object key)
Deprecated.Removes the key and its associated value from this map.- Specified by:
remove
in interfacejava.util.Map
- Overrides:
remove
in classjava.util.AbstractMap
- Parameters:
key
- the key to remove- Returns:
- the value associated with that key, or null if the key was not in the map
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clear
public void clear()
Deprecated.Clears this map.- Specified by:
clear
in interfacejava.util.Map
- Overrides:
clear
in classjava.util.AbstractMap
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entrySet
public java.util.Set entrySet()
Deprecated.Returns a set view of this map's entries.- Specified by:
entrySet
in interfacejava.util.Map
- Specified by:
entrySet
in classjava.util.AbstractMap
- Returns:
- a set view of this map's entries
-
keySet
public java.util.Set keySet()
Deprecated.Returns a set view of this map's keys.- Specified by:
keySet
in interfacejava.util.Map
- Overrides:
keySet
in classjava.util.AbstractMap
- Returns:
- a set view of this map's keys
-
values
public java.util.Collection values()
Deprecated.Returns a collection view of this map's values.- Specified by:
values
in interfacejava.util.Map
- Overrides:
values
in classjava.util.AbstractMap
- Returns:
- a collection view of this map's values.
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