Package com.twelvemonkeys.util
Class LRUMap<K,V>
- java.lang.Object
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- java.util.AbstractMap<K,V>
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- com.twelvemonkeys.util.AbstractDecoratedMap<K,V>
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- com.twelvemonkeys.util.LinkedMap<K,V>
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- com.twelvemonkeys.util.LRUMap<K,V>
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- All Implemented Interfaces:
ExpiringMap<K,V>
,java.io.Serializable
,java.lang.Cloneable
,java.util.Map<K,V>
public class LRUMap<K,V> extends LinkedMap<K,V> implements ExpiringMap<K,V>
Map implementation with size limit, that keeps its entries in LRU (least recently used) order, also known as access-order. When the size limit is reached, the least recently accessed mappings are removed. The number of mappings to be removed from the map, is controlled by the trim factor.- Default size limit is 1000 elements.
See
setMaxSize(int)
/getMaxSize()
. - Default trim factor is 1% (
0.01f
). SeesetTrimFactor(float)
/getTrimFactor()
.
- Version:
- $Id: com/twelvemonkeys/util/LRUMap.java#1 $
- See Also:
- Serialized Form
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Nested Class Summary
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Nested classes/interfaces inherited from class com.twelvemonkeys.util.LinkedMap
LinkedMap.LinkedEntry<K,V>
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Nested classes/interfaces inherited from class com.twelvemonkeys.util.AbstractDecoratedMap
AbstractDecoratedMap.BasicEntry<K,V>, AbstractDecoratedMap.EntrySet, AbstractDecoratedMap.KeySet, AbstractDecoratedMap.Values
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Field Summary
Fields Modifier and Type Field Description private int
maxSize
private float
trimFactor
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Fields inherited from class com.twelvemonkeys.util.LinkedMap
accessOrder, head
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Fields inherited from class com.twelvemonkeys.util.AbstractDecoratedMap
entries, modCount
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Constructor Summary
Constructors Constructor Description LRUMap()
Creates an LRUMap with default max size (1000 entries).LRUMap(int pMaxSize)
Creates an LRUMap with the given max size.LRUMap(java.util.Map<? extends K,? extends V> pContents)
Creates an LRUMap with initial mappings from the given map, and default max size (1000 entries).LRUMap(java.util.Map<? extends K,? extends V> pContents, int pMaxSize)
Creates an LRUMap with initial mappings from the given map, and the given max size.LRUMap(java.util.Map<K,java.util.Map.Entry<K,V>> pBacking, java.util.Map<? extends K,? extends V> pContents, int pMaxSize)
Creates an LRUMap with initial mappings from the given map, and the given max size.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description int
getMaxSize()
Returns the maximum number of mappings in this map.float
getTrimFactor()
Returns the current trim factor.void
processRemoved(java.util.Map.Entry<K,V> pRemoved)
Default implementation does nothing.protected boolean
removeEldestEntry(java.util.Map.Entry pEldest)
always returnsfalse
, and instead invokesremoveLRU()
ifsize >= maxSize
.protected java.util.Map.Entry<K,V>
removeEntry(java.util.Map.Entry<K,V> pEntry)
Removes the given entry from the Map.void
removeLRU()
Removes the least recently used mapping(s) from this map.void
setMaxSize(int pMaxSize)
Sets the maximum number of elements in this map.void
setTrimFactor(float pTrimFactor)
Sets the trim factor.-
Methods inherited from class com.twelvemonkeys.util.LinkedMap
clone, containsValue, createEntry, get, init, newEntryIterator, newKeyIterator, newValueIterator, put, remove
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Methods inherited from class com.twelvemonkeys.util.AbstractDecoratedMap
clear, containsKey, entrySet, getEntry, isEmpty, keySet, size, values
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Constructor Detail
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LRUMap
public LRUMap()
Creates an LRUMap with default max size (1000 entries). This is constructor is here to comply with the reccomendations for "standard" constructors in theMap
interface.- See Also:
LRUMap(int)
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LRUMap
public LRUMap(int pMaxSize)
Creates an LRUMap with the given max size.- Parameters:
pMaxSize
- size limit
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LRUMap
public LRUMap(java.util.Map<? extends K,? extends V> pContents)
Creates an LRUMap with initial mappings from the given map, and default max size (1000 entries). This is constructor is here to comply with the reccomendations for "standard" constructors in theMap
interface.- Parameters:
pContents
- the map whose mappings are to be placed in this map. May benull
.- See Also:
LRUMap(Map, int)
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LRUMap
public LRUMap(java.util.Map<? extends K,? extends V> pContents, int pMaxSize)
Creates an LRUMap with initial mappings from the given map, and the given max size.- Parameters:
pContents
- the map whose mappings are to be placed in this map. May benull
.pMaxSize
- size limit
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LRUMap
public LRUMap(java.util.Map<K,java.util.Map.Entry<K,V>> pBacking, java.util.Map<? extends K,? extends V> pContents, int pMaxSize)
Creates an LRUMap with initial mappings from the given map, and the given max size.- Parameters:
pBacking
- the backing map of this map. Must be either empty, or the same map aspContents
.pContents
- the map whose mappings are to be placed in this map. May benull
.pMaxSize
- max size
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Method Detail
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getMaxSize
public int getMaxSize()
Returns the maximum number of mappings in this map.- Returns:
- the size limit
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setMaxSize
public void setMaxSize(int pMaxSize)
Sets the maximum number of elements in this map. If the current size is greater than the new max size, the map will be trimmed to fit the new max size constraint.- Parameters:
pMaxSize
- new size limit- See Also:
removeLRU()
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getTrimFactor
public float getTrimFactor()
Returns the current trim factor.The trim factor controls how many percent of the maps current size is reclaimed, when performing an
removeLRU
operation. Defaults to 1% (0.01f
).- Returns:
- the current trim factor
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setTrimFactor
public void setTrimFactor(float pTrimFactor)
Sets the trim factor.The trim factor controls how many percent of the maps current size is reclaimed, when performing an
removeLRU
operation. Defaults to 1% (0.01f
).- Parameters:
pTrimFactor
- the new trim factor. Acceptable values are between 0 (inclusive) and 1 (exclusive).- See Also:
removeLRU()
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removeEldestEntry
protected boolean removeEldestEntry(java.util.Map.Entry pEldest)
always returnsfalse
, and instead invokesremoveLRU()
ifsize >= maxSize
.- Overrides:
removeEldestEntry
in classLinkedMap<K,V>
- Parameters:
pEldest
- The least recently inserted entry in the map, or if this is an access-ordered map, the least recently accessed entry. This is the entry that will be removed it this method returnstrue
. If the map was empty prior to theput
orputAll
invocation resulting in this invocation, this will be the entry that was just inserted; in other words, if the map contains a single entry, the eldest entry is also the newest.- Returns:
true
if the eldest entry should be removed from the map;false
if it should be retained.
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removeEntry
protected java.util.Map.Entry<K,V> removeEntry(java.util.Map.Entry<K,V> pEntry)
Description copied from class:AbstractDecoratedMap
Removes the given entry from the Map.- Overrides:
removeEntry
in classAbstractDecoratedMap<K,V>
- Parameters:
pEntry
- the entry to be removed- Returns:
- the removed entry, or
null
if nothing was removed.
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processRemoved
public void processRemoved(java.util.Map.Entry<K,V> pRemoved)
Default implementation does nothing. May be used by clients as a call-back to notify when mappings expire from the map.- Specified by:
processRemoved
in interfaceExpiringMap<K,V>
- Parameters:
pRemoved
- the removed mapping
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removeLRU
public void removeLRU()
Removes the least recently used mapping(s) from this map.How many mappings are removed from the map, is controlled by the trim factor. In any case, at least one mapping will be removed.
- See Also:
getTrimFactor()
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