Class LRUMap<K,V>

java.lang.Object
java.util.AbstractMap<K,V>
com.twelvemonkeys.util.AbstractDecoratedMap<K,V>
com.twelvemonkeys.util.LinkedMap<K,V>
com.twelvemonkeys.util.LRUMap<K,V>
All Implemented Interfaces:
ExpiringMap<K,V>, Serializable, Cloneable, 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.

Version:
$Id: com/twelvemonkeys/util/LRUMap.java#1 $
See Also:

  • Field Details

    • maxSize

      private int maxSize

    • trimFactor

      private float trimFactor

  • Constructor Details

    • 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 the Map interface.
      See Also:

    • LRUMap

      public LRUMap(int pMaxSize)
      Creates an LRUMap with the given max size.
      Parameters:
      pMaxSize - size limit

    • LRUMap

      public LRUMap(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 the Map interface.
      Parameters:
      pContents - the map whose mappings are to be placed in this map. May be null.
      See Also:

    • LRUMap

      public LRUMap(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 be null.
      pMaxSize - size limit

    • LRUMap

      public LRUMap(Map<K, Map.Entry<K,V>> pBacking, 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 as pContents.
      pContents - the map whose mappings are to be placed in this map. May be null.
      pMaxSize - max size

  • Method Details

    • 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:

    • 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:

    • removeEldestEntry

      protected boolean removeEldestEntry(Map.Entry pEldest)
      always returns false, and instead invokes removeLRU() if size >= maxSize.
      Overrides:
      removeEldestEntry in class LinkedMap<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 returns true. If the map was empty prior to the put or putAll 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.

    • removeEntry

      protected Map.Entry<K,V> removeEntry(Map.Entry<K,V> pEntry)
      Description copied from class: AbstractDecoratedMap
      Removes the given entry from the Map.
      Overrides:
      removeEntry in class AbstractDecoratedMap<K,V>
      Parameters:
      pEntry - the entry to be removed
      Returns:
      the removed entry, or null if nothing was removed.

    • processRemoved

      public void processRemoved(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 interface ExpiringMap<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: