Package org.pentaho.reporting.libraries.base.util

Class LFUMap<K,V>

java.lang.Object
org.pentaho.reporting.libraries.base.util.LFUMap<K,V>
All Implemented Interfaces:
Serializable, Cloneable
public class LFUMap<K,V> extends Object implements Serializable, Cloneable
A Least-Frequently-Used Map.

This is not a real map in the sense of the Java-Collections-API. This is a slimmed down version of a Least-Frequently-Used map with no unnecessary extra stuff like iterators or other costly but rarely used java.util.Collections features. The cache does not accept null-keys, and any attempt to store null-values will yield an error.

To remove a couple of ugly checks and thus improving performance, this map enforces a minimum size of 3 items.

Author:
Thomas Morgner
See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    LFUMap(int cacheSize)
    Creates a new LFU-Map with a maximum size of cacheSize entries.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    clear()
     
    Object
    clone()
     
    V
    get(K key)
    Return the entry for the given key.
    int
    getMaximumSize()
    Returns the defined maximum size.
    boolean
    isEmpty()
    Checks whether this map is empty.
    void
    put(K key, V value)
    Puts the given value into the map using the specified non-null key.
    void
    remove(K key)
    Removes the entry for the given key.
    int
    size()
    Returns the number of items in this map.
    void
    validate()
    Validates the map's internal datastructures.

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • LFUMap

      public LFUMap(int cacheSize)
      Creates a new LFU-Map with a maximum size of cacheSize entries.
      Parameters:
      cacheSize - the maximum number of elements this map will be able to store.

  • Method Details

    • clear

      public void clear()

    • get

      public V get(K key)
      Return the entry for the given key. Any successful lookup moves the entry to the top of the list.
      Parameters:
      key - the lookup key.
      Returns:
      the value stored for the key or null.

    • put

      public void put(K key, V value)
      Puts the given value into the map using the specified non-null key. The new entry is added as first entry in the list of recently used values.
      Parameters:
      key - the key.
      value - the value.

    • remove

      public void remove(K key)
      Removes the entry for the given key.
      Parameters:
      key - the key for which an entry should be removed.

    • size

      public int size()
      Returns the number of items in this map.
      Returns:
      the number of items in the map.

    • isEmpty

      public boolean isEmpty()
      Checks whether this map is empty.
      Returns:
      true, if the map is empty, false otherwise.

    • getMaximumSize

      public int getMaximumSize()
      Returns the defined maximum size.
      Returns:
      the defines maximum size.

    • validate

      public void validate()
      Validates the map's internal datastructures. There should be no need to call this method manually.

    • clone

      public Object clone() throws CloneNotSupportedException
      Overrides:
      clone in class Object
      Throws:
      CloneNotSupportedException