Class LRUMap
- java.lang.Object
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- org.apache.commons.collections.SequencedHashMap
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- org.apache.commons.collections.LRUMap
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- All Implemented Interfaces:
java.io.Externalizable
,java.io.Serializable
,java.lang.Cloneable
,java.util.Map
public class LRUMap extends SequencedHashMap implements java.io.Externalizable
Deprecated.Moved to map subpackage. Due to be removed in v4.0.An implementation of a Map which has a maximum size and uses a Least Recently Used algorithm to remove items from the Map when the maximum size is reached and new items are added.
A synchronized version can be obtained with:
Collections.synchronizedMap( theMapToSynchronize )
If it will be accessed by multiple threads, you _must_ synchronize access to this Map. Even concurrent get(Object) operations produce indeterminate behaviour.Unlike the Collections 1.0 version, this version of LRUMap does use a true LRU algorithm. The keys for all gets and puts are moved to the front of the list. LRUMap is now a subclass of SequencedHashMap, and the "LRU" key is now equivalent to LRUMap.getFirst().
- Since:
- Commons Collections 1.0
- Version:
- $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description private int
maximumSize
Deprecated.private static long
serialVersionUID
Deprecated.
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Method Summary
All Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description java.lang.Object
get(java.lang.Object key)
Deprecated.Get the value for a key from the Map.int
getMaximumSize()
Deprecated.Getter for property maximumSize.protected void
processRemovedLRU(java.lang.Object key, java.lang.Object value)
Deprecated.Subclasses of LRUMap may hook into this method to provide specialized actions whenever an Object is automatically removed from the cache.java.lang.Object
put(java.lang.Object key, java.lang.Object value)
Deprecated.Removes the key and its Object from the Map.void
readExternal(java.io.ObjectInput in)
Deprecated.Deserializes this map from the given stream.protected void
removeLRU()
Deprecated.This method is used internally by the class for finding and removing the LRU Object.void
setMaximumSize(int maximumSize)
Deprecated.Setter for property maximumSize.void
writeExternal(java.io.ObjectOutput out)
Deprecated.Serializes this map to the given stream.-
Methods inherited from class org.apache.commons.collections.SequencedHashMap
clear, clone, containsKey, containsValue, entrySet, equals, get, getFirst, getFirstKey, getFirstValue, getLast, getLastKey, getLastValue, getValue, hashCode, indexOf, isEmpty, iterator, keySet, lastIndexOf, putAll, remove, remove, sequence, size, toString, values
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Field Detail
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maximumSize
private int maximumSize
Deprecated.
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serialVersionUID
private static final long serialVersionUID
Deprecated.- See Also:
- Constant Field Values
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Constructor Detail
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LRUMap
public LRUMap()
Deprecated.Default constructor, primarily for the purpose of de-externalization. This constructors sets a default LRU limit of 100 keys, but this value may be overridden internally as a result of de-externalization.
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LRUMap
public LRUMap(int i)
Deprecated.Create a new LRUMap with a maximum capacity of i. Once i capacity is achieved, subsequent gets and puts will push keys out of the map. See .- Parameters:
i
- Maximum capacity of the LRUMap
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Method Detail
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get
public java.lang.Object get(java.lang.Object key)
Deprecated.Get the value for a key from the Map. The key will be promoted to the Most Recently Used position. Note that get(Object) operations will modify the underlying Collection. Calling get(Object) inside of an iteration over keys, values, etc. is currently unsupported.
- Specified by:
get
in interfacejava.util.Map
- Overrides:
get
in classSequencedHashMap
- Parameters:
key
- Key to retrieve- Returns:
- Returns the value. Returns null if the key has a null value or if the key has no value.
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put
public java.lang.Object put(java.lang.Object key, java.lang.Object value)
Deprecated.Removes the key and its Object from the Map.
(Note: this may result in the "Least Recently Used" object being removed from the Map. In that case, the removeLRU() method is called. See javadoc for removeLRU() for more details.)
- Specified by:
put
in interfacejava.util.Map
- Overrides:
put
in classSequencedHashMap
- Parameters:
key
- Key of the Object to add.value
- Object to add- Returns:
- Former value of the key
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removeLRU
protected void removeLRU()
Deprecated.This method is used internally by the class for finding and removing the LRU Object.
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processRemovedLRU
protected void processRemovedLRU(java.lang.Object key, java.lang.Object value)
Deprecated.Subclasses of LRUMap may hook into this method to provide specialized actions whenever an Object is automatically removed from the cache. By default, this method does nothing.- Parameters:
key
- key that was removedvalue
- value of that key (can be null)
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readExternal
public void readExternal(java.io.ObjectInput in) throws java.io.IOException, java.lang.ClassNotFoundException
Deprecated.Description copied from class:SequencedHashMap
Deserializes this map from the given stream.- Specified by:
readExternal
in interfacejava.io.Externalizable
- Overrides:
readExternal
in classSequencedHashMap
- Parameters:
in
- the stream to deserialize from- Throws:
java.io.IOException
- if the stream raises itjava.lang.ClassNotFoundException
- if the stream raises it
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writeExternal
public void writeExternal(java.io.ObjectOutput out) throws java.io.IOException
Deprecated.Description copied from class:SequencedHashMap
Serializes this map to the given stream.- Specified by:
writeExternal
in interfacejava.io.Externalizable
- Overrides:
writeExternal
in classSequencedHashMap
- Parameters:
out
- the stream to serialize to- Throws:
java.io.IOException
- if the stream raises it
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getMaximumSize
public int getMaximumSize()
Deprecated.Getter for property maximumSize.- Returns:
- Value of property maximumSize.
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setMaximumSize
public void setMaximumSize(int maximumSize)
Deprecated.Setter for property maximumSize.- Parameters:
maximumSize
- New value of property maximumSize.
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