Package com.fasterxml.jackson.databind.util

Class LRUMap<K,​V>

  • All Implemented Interfaces:
    LookupCache<K,​V>, java.io.Serializable
    public class LRUMap<K,​V>
extends java.lang.Object
implements LookupCache<K,​V>, java.io.Serializable
    Helper for simple bounded maps used for reusing lookup values.

    Note that serialization behavior is such that contents are NOT serialized, on assumption that all use cases are for caching where persistence does not make sense. The only thing serialized is the cache size of Map.

    Since Jackson 2.12, there has been pluggable LookupCache interface which allows users, frameworks, provide their own cache implementations.

    Since Jackson 2.14, the implementation

    • Evicts the least recently used entry when max size is reached
    • Is thread-safe and does NOT require external synchronization
    See Also:
    Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      LRUMap​(int initialEntries, int maxEntries)  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()
      Method for removing all contents this cache has.
      void contents​(java.util.function.BiConsumer<K,​V> consumer)
      Method to apply operation on cache contents without exposing them.
      LookupCache<K,​V> emptyCopy()
      Method needed for creating clones but without contents.
      V get​(java.lang.Object key)
      NOTE: key is of type Object only to retain binary backwards-compatibility
      V put​(K key, V value)  
      V putIfAbsent​(K key, V value)  
      int size()  

      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • LRUMap

        public LRUMap​(int initialEntries,
              int maxEntries)

    • Method Detail

      • emptyCopy

        public LookupCache<K,​V> emptyCopy()
        Description copied from interface: LookupCache
        Method needed for creating clones but without contents.

        Default implementation throws UnsupportedOperationException. Implementations are required to override this method.

        Specified by:
        emptyCopy in interface LookupCache<K,​V>

      • get

        public V get​(java.lang.Object key)
        Description copied from interface: LookupCache
        NOTE: key is of type Object only to retain binary backwards-compatibility
        Specified by:
        get in interface LookupCache<K,​V>
        Returns:
        value associated with key (can return null)

      • clear

        public void clear()
        Description copied from interface: LookupCache
        Method for removing all contents this cache has.
        Specified by:
        clear in interface LookupCache<K,​V>

      • size

        public int size()
        Specified by:
        size in interface LookupCache<K,​V>
        Returns:
        Number of entries currently in cache: may be approximate, only to be used for diagnostics, metrics reporting

      • contents

        public void contents​(java.util.function.BiConsumer<K,​V> consumer)
        Description copied from interface: LookupCache
        Method to apply operation on cache contents without exposing them.

        Default implementation throws UnsupportedOperationException. Implementations are required to override this method.

        Specified by:
        contents in interface LookupCache<K,​V>
        Parameters:
        consumer - Operation to apply on cache contents.