Package org.simpleframework.common

Class LeastRecentlyUsedMap<K,V>

java.lang.Object

java.util.AbstractMap<K,V>

java.util.HashMap<K,V>

java.util.LinkedHashMap<K,V>

org.simpleframework.common.LeastRecentlyUsedMap<K,V>

All Implemented Interfaces:

Serializable, Cloneable, Map<K,V>, SequencedMap<K,V>

public class LeastRecentlyUsedMap<K,V>
extends LinkedHashMap<K,V>

The LeastRecentlyUsedMap is a hash map that keeps only those entries most recently used. This acts much like a hot spot cache for specific keys that are used frequently. It also allows for algorithms to keep hot spot values available in the cache without the risk of running out of memory.

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	LeastRecentlyUsedMap.RemovalListener<K,V>	The RemovalListener is used with the least recently used hash map to listen for removals.

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

AbstractMap.SimpleEntry<K,V>, AbstractMap.SimpleImmutableEntry<K,V>

Field Summary

Fields

Modifier and Type	Field	Description
private final int	capacity	This is the number of items to keep within the cache.
private final LeastRecentlyUsedMap.RemovalListener<K,V>	listener	This is the listener that is called when an entry is removed.

Constructor Summary

Constructors

Constructor	Description
LeastRecentlyUsedMap()	Constructor for the LeastRecentlyUsedMap object.
LeastRecentlyUsedMap(int capacity)	Constructor for the LeastRecentlyUsedMap object.
LeastRecentlyUsedMap(LeastRecentlyUsedMap.RemovalListener<K,V> listener)	Constructor for the LeastRecentlyUsedMap object.
LeastRecentlyUsedMap(LeastRecentlyUsedMap.RemovalListener<K,V> listener, int capacity)	Constructor for the LeastRecentlyUsedMap object.

Method Summary

Modifier and Type	Method	Description
protected boolean	removeEldestEntry(Map.Entry<K,V> eldest)	This is used to determine if an entry should be removed from the cache.

Methods inherited from class java.util.LinkedHashMap

clear, containsValue, entrySet, forEach, get, getOrDefault, keySet, newLinkedHashMap, putFirst, putLast, replaceAll, reversed, sequencedEntrySet, sequencedKeySet, sequencedValues, values

Methods inherited from class java.util.HashMap

clone, compute, computeIfAbsent, computeIfPresent, containsKey, isEmpty, merge, newHashMap, put, putAll, putIfAbsent, remove, remove, replace, replace, size

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

compute, computeIfAbsent, computeIfPresent, containsKey, equals, hashCode, isEmpty, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, size

Methods inherited from interface java.util.SequencedMap

firstEntry, lastEntry, pollFirstEntry, pollLastEntry

Field Details

listener

private final LeastRecentlyUsedMap.RemovalListener<K,V> listener

This is the listener that is called when an entry is removed.

capacity

private final int capacity

This is the number of items to keep within the cache.

Constructor Details

LeastRecentlyUsedMap

public LeastRecentlyUsedMap()

Constructor for the LeastRecentlyUsedMap object. This creates a hash container that keeps only those entries that have been recently added or accessed available within the collection.

LeastRecentlyUsedMap

public LeastRecentlyUsedMap(int capacity)

Constructor for the LeastRecentlyUsedMap object. This creates a hash container that keeps only those entries that have been recently added or accessed available within the collection.

Parameters:

capacity - this is the capacity of the hash container

LeastRecentlyUsedMap

public LeastRecentlyUsedMap(LeastRecentlyUsedMap.RemovalListener<K,V> listener)

Constructor for the LeastRecentlyUsedMap object. This creates a hash container that keeps only those entries that have been recently added or accessed available within the collection.

Parameters:

listener - this listens for entries that are removed

LeastRecentlyUsedMap

public LeastRecentlyUsedMap(LeastRecentlyUsedMap.RemovalListener<K,V> listener,
 int capacity)

Constructor for the LeastRecentlyUsedMap object. This creates a hash container that keeps only those entries that have been recently added or accessed available within the collection.

Parameters:

listener - this listens for entries that are removed

capacity - this is the capacity of the hash container

Method Details

removeEldestEntry

protected boolean removeEldestEntry(Map.Entry<K,V> eldest)

This is used to determine if an entry should be removed from the cache. If the cache has reached its capacity then the listener, if one was specified is given a callback to tell any other participating objects the entry has been removed.

Overrides:

removeEldestEntry in class LinkedHashMap<K,V>

Parameters:

eldest - this is the candidate for removal