Class LRUMap<K,​V>

  • 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.

    Version:
    $Id: com/twelvemonkeys/util/LRUMap.java#1 $
    Author:
    Harald Kuhr
    See Also:
    Serialized Form
    • Nested Class Summary

      • Nested classes/interfaces inherited from class java.util.AbstractMap

        java.util.AbstractMap.SimpleEntry<K extends java.lang.Object,​V extends java.lang.Object>, java.util.AbstractMap.SimpleImmutableEntry<K extends java.lang.Object,​V extends java.lang.Object>
      • Nested classes/interfaces inherited from interface java.util.Map

        java.util.Map.Entry<K extends java.lang.Object,​V extends java.lang.Object>
    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected java.util.Map<K,​java.util.Map.Entry<K,​V>> entries  
      protected int modCount  
    • 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.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()  
      boolean containsKey​(java.lang.Object pKey)  
      java.util.Set<java.util.Map.Entry<K,​V>> entrySet()  
      int getMaxSize()
      Returns the maximum number of mappings in this map.
      float getTrimFactor()
      Returns the current trim factor.
      boolean isEmpty()  
      java.util.Set<K> keySet()  
      void processRemoved​(java.util.Map.Entry<K,​V> pRemoved)
      Default implementation does nothing.
      protected boolean removeEldestEntry​(java.util.Map.Entry pEldest)
      always returns false, and instead invokes removeLRU() if size >= 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.
      int size()  
      java.util.Collection<V> values()  
      • Methods inherited from class java.util.AbstractMap

        equals, hashCode, putAll, toString
      • Methods inherited from class java.lang.Object

        finalize, getClass, notify, notifyAll, wait, wait, wait
      • Methods inherited from interface java.util.Map

        clear, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, entrySet, equals, forEach, get, getOrDefault, hashCode, isEmpty, keySet, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll, size, values
    • Field Detail

      • entries

        protected java.util.Map<K,​java.util.Map.Entry<K,​V>> entries
      • modCount

        protected transient volatile int modCount
    • Constructor Detail

      • 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(int)
      • LRUMap

        public LRUMap​(int pMaxSize)
        Creates an LRUMap with the given max size.
        Parameters:
        pMaxSize - size limit
      • 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 the Map interface.
        Parameters:
        pContents - the map whose mappings are to be placed in this map. May be null.
        See Also:
        LRUMap(Map, int)
      • 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 be null.
        pMaxSize - size limit
      • 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 as pContents.
        pContents - the map whose mappings are to be placed in this map. May be null.
        pMaxSize - max size
    • 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 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 java.util.Map.Entry<K,​V> removeEntry​(java.util.Map.Entry<K,​V> pEntry)
        Removes the given entry from the Map.
        Parameters:
        pEntry - the entry to be removed
        Returns:
        the removed entry, or null if nothing was removed.
      • 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 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:
        getTrimFactor()
      • size

        public int size()
        Specified by:
        size in interface java.util.Map<K,​V>
        Overrides:
        size in class java.util.AbstractMap<K,​V>
      • clear

        public void clear()
        Specified by:
        clear in interface java.util.Map<K,​V>
        Overrides:
        clear in class java.util.AbstractMap<K,​V>
      • isEmpty

        public boolean isEmpty()
        Specified by:
        isEmpty in interface java.util.Map<K,​V>
        Overrides:
        isEmpty in class java.util.AbstractMap<K,​V>
      • containsKey

        public boolean containsKey​(java.lang.Object pKey)
        Specified by:
        containsKey in interface java.util.Map<K,​V>
        Overrides:
        containsKey in class java.util.AbstractMap<K,​V>
      • values

        public java.util.Collection<V> values()
        Specified by:
        values in interface java.util.Map<K,​V>
        Overrides:
        values in class java.util.AbstractMap<K,​V>
      • entrySet

        public java.util.Set<java.util.Map.Entry<K,​V>> entrySet()
        Specified by:
        entrySet in interface java.util.Map<K,​V>
        Specified by:
        entrySet in class java.util.AbstractMap<K,​V>
      • keySet

        public java.util.Set<K> keySet()
        Specified by:
        keySet in interface java.util.Map<K,​V>
        Overrides:
        keySet in class java.util.AbstractMap<K,​V>