Package org.apache.commons.collections.map

Class LRUMap

java.lang.Object
java.util.AbstractMap
org.apache.commons.collections.map.AbstractHashedMap
org.apache.commons.collections.map.AbstractLinkedMap
org.apache.commons.collections.map.LRUMap
All Implemented Interfaces:
Serializable, Cloneable, Map, BoundedMap, IterableMap, OrderedMap
@Deprecated(since="2021-04-30") public class LRUMap extends AbstractLinkedMap implements BoundedMap, Serializable, Cloneable
Deprecated.
Apache Commons Collections version 3.x is being deprecated from AEMaaCS. The upgraded version 4.4 of Commons Collections is already included as replacement. Customers are advised to upgrade to this version of the library. Please note: the package name was changed to org.apache.commons.collections4. Further note that there are AEM APIs currently exposing the old collections classes; these will be updated in upcoming releases.
A Map implementation with a fixed maximum size which removes the least recently used entry if an entry is added when full.

The least recently used algorithm works on the get and put operations only. Iteration of any kind, including setting the value by iteration, does not change the order. Queries such as containsKey and containsValue or access via views also do not change the order.

The map implements OrderedMap and entries may be queried using the bidirectional OrderedMapIterator. The order returned is least recently used to most recently used. Iterators from map views can also be cast to OrderedIterator if required.

All the available iterators can be reset back to the start by casting to ResettableIterator and calling reset().

Note that LRUMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. The simplest approach is to wrap this map using Collections.synchronizedMap(Map). This class may throw NullPointerException's when accessed by concurrent threads.

Since:
Commons Collections 3.0 (previously in main package v1.0)
See Also:

  • Constructor Details

    • LRUMap

      public LRUMap()
      Deprecated.
      Constructs a new empty map with a maximum size of 100.

    • LRUMap

      public LRUMap(int maxSize)
      Deprecated.
      Constructs a new, empty map with the specified maximum size.
      Parameters:
      maxSize - the maximum size of the map
      Throws:
      IllegalArgumentException - if the maximum size is less than one

    • LRUMap

      public LRUMap(int maxSize, boolean scanUntilRemovable)
      Deprecated.
      Constructs a new, empty map with the specified maximum size.
      Parameters:
      maxSize - the maximum size of the map
      scanUntilRemovable - scan until a removeable entry is found, default false
      Throws:
      IllegalArgumentException - if the maximum size is less than one
      Since:
      Commons Collections 3.1

    • LRUMap

      public LRUMap(int maxSize, float loadFactor)
      Deprecated.
      Constructs a new, empty map with the specified initial capacity and load factor.
      Parameters:
      maxSize - the maximum size of the map, -1 for no limit,
      loadFactor - the load factor
      Throws:
      IllegalArgumentException - if the maximum size is less than one
      IllegalArgumentException - if the load factor is less than zero

    • LRUMap

      public LRUMap(int maxSize, float loadFactor, boolean scanUntilRemovable)
      Deprecated.
      Constructs a new, empty map with the specified initial capacity and load factor.
      Parameters:
      maxSize - the maximum size of the map, -1 for no limit,
      loadFactor - the load factor
      scanUntilRemovable - scan until a removeable entry is found, default false
      Throws:
      IllegalArgumentException - if the maximum size is less than one
      IllegalArgumentException - if the load factor is less than zero
      Since:
      Commons Collections 3.1

    • LRUMap

      public LRUMap(Map map)
      Deprecated.
      Constructor copying elements from another map.

      The maximum size is set from the map's size.

      Parameters:
      map - the map to copy
      Throws:
      NullPointerException - if the map is null
      IllegalArgumentException - if the map is empty

    • LRUMap

      public LRUMap(Map map, boolean scanUntilRemovable)
      Deprecated.
      Constructor copying elements from another map.

      The maximum size is set from the map's size.

      Parameters:
      map - the map to copy
      scanUntilRemovable - scan until a removeable entry is found, default false
      Throws:
      NullPointerException - if the map is null
      IllegalArgumentException - if the map is empty
      Since:
      Commons Collections 3.1

  • Method Details

    • get

      public Object get(Object key)
      Deprecated.
      Gets the value mapped to the key specified.

      This operation changes the position of the key in the map to the most recently used position (first).

      Specified by:
      get in interface Map
      Overrides:
      get in class AbstractHashedMap
      Parameters:
      key - the key
      Returns:
      the mapped value, null if no match

    • isFull

      public boolean isFull()
      Deprecated.
      Returns true if this map is full and no new mappings can be added.
      Specified by:
      isFull in interface BoundedMap
      Returns:
      true if the map is full

    • maxSize

      public int maxSize()
      Deprecated.
      Gets the maximum size of the map (the bound).
      Specified by:
      maxSize in interface BoundedMap
      Returns:
      the maximum number of elements the map can hold

    • isScanUntilRemovable

      public boolean isScanUntilRemovable()
      Deprecated.
      Whether this LRUMap will scan until a removable entry is found when the map is full.
      Returns:
      true if this map scans
      Since:
      Commons Collections 3.1

    • clone

      public Object clone()
      Deprecated.
      Clones the map without cloning the keys or values.
      Returns:
      a shallow clone