Class SynchronizedLRUMap
- java.lang.Object
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- org.apache.directory.api.util.SequencedHashMap
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- org.apache.directory.api.util.SynchronizedLRUMap
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- All Implemented Interfaces:
Externalizable
,Serializable
,Cloneable
,Map
public final class SynchronizedLRUMap extends SequencedHashMap implements Externalizable
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
- Author:
- Apache Directory Project
- See Also:
- Serialized Form
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Constructor Summary
Constructors Constructor Description SynchronizedLRUMap()
Default constructor, primarily for the purpose of de-externalization.SynchronizedLRUMap(int i)
Create a new LRUMap with a maximum capacity of i.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description Object
get(Object key)
Get the value for a key from the Map.int
getMaximumSize()
Getter for property maximumSize.Object
put(Object key, Object value)
Removes the key and its Object from the Map.void
setMaximumSize(int maximumSize)
Setter for property maximumSize.-
Methods inherited from class org.apache.directory.api.util.SequencedHashMap
clear, clone, containsKey, containsValue, entrySet, equals, get, getFirst, getFirstKey, getFirstValue, getLast, getLastKey, getLastValue, getValue, hashCode, indexOf, isEmpty, iterator, keySet, lastIndexOf, putAll, readExternal, remove, remove, sequence, size, toString, values, writeExternal
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Methods inherited from interface java.io.Externalizable
readExternal, writeExternal
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Methods inherited from interface java.util.Map
compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll
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Constructor Detail
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SynchronizedLRUMap
public SynchronizedLRUMap()
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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SynchronizedLRUMap
public SynchronizedLRUMap(int i)
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 Object get(Object key)
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 interfaceMap
- 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 Object put(Object key, Object value)
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 interfaceMap
- 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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getMaximumSize
public int getMaximumSize()
Getter for property maximumSize.- Returns:
- Value of property maximumSize.
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setMaximumSize
public void setMaximumSize(int maximumSize)
Setter for property maximumSize.- Parameters:
maximumSize
- New value of property maximumSize.
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