Package com.twelvemonkeys.util
Class LRUHashMap<K,V>
- java.lang.Object
-
- java.util.AbstractMap<K,V>
-
- java.util.HashMap<K,V>
-
- java.util.LinkedHashMap<K,V>
-
- com.twelvemonkeys.util.LRUHashMap<K,V>
-
- All Implemented Interfaces:
ExpiringMap<K,V>
,java.io.Serializable
,java.lang.Cloneable
,java.util.Map<K,V>
public class LRUHashMap<K,V> extends java.util.LinkedHashMap<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: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/util/LRUHashMap.java#1 $
- See Also:
- Serialized Form
-
-
Field Summary
Fields Modifier and Type Field Description private int
maxSize
private float
trimFactor
-
Constructor Summary
Constructors Constructor Description LRUHashMap()
Creates an LRUHashMap with default max size (1000 entries).LRUHashMap(int pMaxSize)
Creates an LRUHashMap with the given max size.LRUHashMap(java.util.Map<? extends K,? extends V> pContents)
Creates an LRUHashMap with initial mappings from the given map, and default max size (1000 entries).LRUHashMap(java.util.Map<? extends K,? extends V> pContents, int pMaxSize)
Creates an LRUHashMap with initial mappings from the given map, and the given max size.
-
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<K,V> pEldest)
always returnsfalse
, and instead invokesremoveLRU()
ifsize >= maxSize
.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 java.util.LinkedHashMap
clear, containsValue, entrySet, forEach, get, getOrDefault, keySet, replaceAll, values
-
Methods inherited from class java.util.HashMap
clone, compute, computeIfAbsent, computeIfPresent, containsKey, isEmpty, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, size
-
-
-
-
Constructor Detail
-
LRUHashMap
public LRUHashMap()
Creates an LRUHashMap with default max size (1000 entries). This is constructor is here to comply with the reccomendations for "standard" constructors in theMap
interface.- See Also:
LRUHashMap(int)
-
LRUHashMap
public LRUHashMap(int pMaxSize)
Creates an LRUHashMap with the given max size.- Parameters:
pMaxSize
- size limit
-
LRUHashMap
public LRUHashMap(java.util.Map<? extends K,? extends V> pContents)
Creates an LRUHashMap 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:
LRUHashMap(java.util.Map, int)
-
-
Method Detail
-
getMaxSize
public int getMaxSize()
Returns the maximum number of mappings in this map.- Returns:
- the size limit
-
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()
-
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
-
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()
-
removeEldestEntry
protected boolean removeEldestEntry(java.util.Map.Entry<K,V> pEldest)
always returnsfalse
, and instead invokesremoveLRU()
ifsize >= maxSize
.
-
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
-
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()
-
-