Package com.cedarsoftware.util.cache

Class ThreadedLRUCacheStrategy<K,V>

java.lang.Object

com.cedarsoftware.util.cache.ThreadedLRUCacheStrategy<K,V>

All Implemented Interfaces:

Map<K,V>

public class ThreadedLRUCacheStrategy<K,V>
extends Object
implements Map<K,V>

This class provides a thread-safe Least Recently Used (LRU) cache API that evicts the least recently used items once a threshold is met. It implements the Map interface for convenience.

The Threaded strategy allows for O(1) access for get(), put(), and remove() without blocking. It uses a ConcurrentHashMap internally. To ensure that the capacity is honored, whenever put() is called, a thread (from a thread pool) is tasked with cleaning up items above the capacity threshold. This means that the cache may temporarily exceed its capacity, but it will soon be trimmed back to the capacity limit by the scheduled thread.

LRUCache supports null for both key and value.

Author:

John DeRegnaucourt ([email protected])
Copyright (c) Cedar Software LLC

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

License

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map

Map.Entry<K,V>

Constructor Summary

Constructors

Constructor	Description
ThreadedLRUCacheStrategy(int capacity, int cleanupDelayMillis, ScheduledExecutorService scheduler)	Create a LRUCache with the maximum capacity of 'capacity.' Note, the LRUCache could temporarily exceed the capacity; however, it will quickly reduce to that amount.

Method Summary

Modifier and Type	Method	Description
void	clear()
boolean	containsKey(Object key)
boolean	containsValue(Object value)
Set<Map.Entry<K,V>>	entrySet()
boolean	equals(Object o)
V	get(Object key)
int	hashCode()
boolean	isEmpty()
Set<K>	keySet()
V	put(K key, V value)
void	putAll(Map<? extends K,? extends V> m)
V	remove(Object key)
void	shutdown()	Shut down the scheduler if it is the default one.
int	size()
String	toString()
Collection<V>	values()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Map

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Constructor Details

ThreadedLRUCacheStrategy

public ThreadedLRUCacheStrategy(int capacity,
 int cleanupDelayMillis,
 ScheduledExecutorService scheduler)

Create a LRUCache with the maximum capacity of 'capacity.' Note, the LRUCache could temporarily exceed the capacity; however, it will quickly reduce to that amount. This time is configurable via the cleanupDelay parameter and custom scheduler and executor services.

Parameters:

capacity - int maximum size for the LRU cache.

cleanupDelayMillis - int milliseconds before scheduling a cleanup (reduction to capacity if the cache currently exceeds it).

scheduler - ScheduledExecutorService for scheduling cleanup tasks. Can be null. If none is supplied, a default scheduler is created for you. Calling the .shutdown() method will shutdown the schedule only if you passed in null (using default). If you pass one in, it is your responsibility to terminate the scheduler.

Method Details

get

public V get(Object key)

Specified by:

get in interface Map<K,V>

put

public V put(K key,
 V value)

Specified by:

put in interface Map<K,V>

putAll

public void putAll(Map<? extends K,? extends V> m)

Specified by:

putAll in interface Map<K,V>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Map<K,V>

remove

public V remove(Object key)

Specified by:

remove in interface Map<K,V>

clear

public void clear()

Specified by:

clear in interface Map<K,V>

size

public int size()

Specified by:

size in interface Map<K,V>

containsKey

public boolean containsKey(Object key)

Specified by:

containsKey in interface Map<K,V>

containsValue

public boolean containsValue(Object value)

Specified by:

containsValue in interface Map<K,V>

entrySet

public Set<Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface Map<K,V>

keySet

public Set<K> keySet()

Specified by:

keySet in interface Map<K,V>

values

public Collection<V> values()

Specified by:

values in interface Map<K,V>

equals

public boolean equals(Object o)

Specified by:

equals in interface Map<K,V>

Overrides:

equals in class Object

hashCode

public int hashCode()

Specified by:

hashCode in interface Map<K,V>

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

shutdown

public void shutdown()

Shut down the scheduler if it is the default one.