Package net.sourceforge.jtds.jdbc.cache

Class SimpleLRUCache

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Cloneable, java.util.Map
    public class SimpleLRUCache
extends java.util.HashMap
    Simple LRU cache for any type of object. Implemented as an extended HashMap with a maximum size and an aggregated List as LRU queue.
    Version:
    $Id: SimpleLRUCache.java,v 1.1 2005/04/25 11:46:56 alin_sinpalean Exp $
    Author:
    Brett Wooldridge
    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
      private java.util.LinkedList list
      LRU list.
      private int maxCacheSize
      Maximum cache size.

    • Constructor Summary

      Constructors 
      Constructor Description
      SimpleLRUCache​(int maxCacheSize)
      Constructs a new LRU cache instance.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()
      Overrides clear() to also clear the LRU list.
      private void freshenKey​(java.lang.Object key)
      Moves the specified value to the top of the LRU list (the bottom of the list is where least recently used items live).
      java.lang.Object get​(java.lang.Object key)
      Overrides get() so that it also updates the LRU list.
      java.lang.Object put​(java.lang.Object key, java.lang.Object value)
      Overrides put() so that it also updates the LRU list.
      java.lang.Object remove​(java.lang.Object key)  

      • Methods inherited from class java.util.HashMap

        clone, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, entrySet, forEach, getOrDefault, isEmpty, keySet, merge, putAll, putIfAbsent, remove, replace, replace, replaceAll, size, values

      • Methods inherited from class java.util.AbstractMap

        equals, hashCode, toString

      • Methods inherited from class java.lang.Object

        finalize, getClass, notify, notifyAll, wait, wait, wait

      • Methods inherited from interface java.util.Map

        equals, hashCode

    • Field Detail

      • maxCacheSize

        private final int maxCacheSize
        Maximum cache size.

      • list

        private final java.util.LinkedList list
        LRU list.

    • Constructor Detail

      • SimpleLRUCache

        public SimpleLRUCache​(int maxCacheSize)
        Constructs a new LRU cache instance.
        Parameters:
        maxCacheSize - the maximum number of entries in this cache before entries are aged off

    • Method Detail

      • clear

        public void clear()
        Overrides clear() to also clear the LRU list.
        Specified by:
        clear in interface java.util.Map
        Overrides:
        clear in class java.util.HashMap

      • put

        public java.lang.Object put​(java.lang.Object key,
                            java.lang.Object value)
        Overrides put() so that it also updates the LRU list.
        Specified by:
        put in interface java.util.Map
        Overrides:
        put in class java.util.HashMap
        Parameters:
        key - key with which the specified value is to be associated
        value - value to be associated with the key
        Returns:
        previous value associated with key or null if there was no mapping for key; a null return can also indicate that the cache previously associated null with the specified key
        See Also:
        Map.put(Object, Object)

      • get

        public java.lang.Object get​(java.lang.Object key)
        Overrides get() so that it also updates the LRU list.
        Specified by:
        get in interface java.util.Map
        Overrides:
        get in class java.util.HashMap
        Parameters:
        key - key with which the expected value is associated
        Returns:
        the value to which the cache maps the specified key, or null if the map contains no mapping for this key

      • remove

        public java.lang.Object remove​(java.lang.Object key)
        Specified by:
        remove in interface java.util.Map
        Overrides:
        remove in class java.util.HashMap
        See Also:
        Map.remove(Object)

      • freshenKey

        private void freshenKey​(java.lang.Object key)
        Moves the specified value to the top of the LRU list (the bottom of the list is where least recently used items live).
        Parameters:
        key - key of the value to move to the top of the list