org.camunda.commons.utils.cache
Class ConcurrentLruCache<K,V>

java.lang.Object
  org.camunda.commons.utils.cache.ConcurrentLruCache<K,V>

Type Parameters:

K - the type of keys

V - the type of mapped values

All Implemented Interfaces:

Cache<K,V>

public class ConcurrentLruCache<K,V>
extends Object
implements Cache<K,V>

A thread-safe LRU Cache with a fixed capacity. If the cache reaches the capacity, it discards the least recently used entry first.

*Note*: The consistency of the keys queue with the keys in the cache is not ensured! This means, the keys queue can contain duplicates of the same key and not all the keys of the queue are necessarily in the cache. However, all the keys of the cache are at least once contained in the keys queue.

Constructor Summary

ConcurrentLruCache(int capacity)
Creates the cache with a fixed capacity.

Method Summary

void	clear() Clears the contents of the cache.
V	get(K key) Gets an entry from the cache.
boolean	isEmpty() Returns true if this cache contains no key-value mappings.
Set<K>	keySet() Returns a Set view of the keys contained in this cache.
void	put(K key, V value) Associates the specified value with the specified key in the cache.
void	remove(K key) Removes an entry from the cache.
protected void	removeAll(K key) Removes all instances of the given key within the keys queue.
int	size()

Methods inherited from class java.lang.Object

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

Constructor Detail

ConcurrentLruCache

public ConcurrentLruCache(int capacity)

Creates the cache with a fixed capacity.

Parameters:

capacity - max number of cache entries

Throws:

IllegalArgumentException - if capacity is negative

Method Detail

get

public V get(K key)

Description copied from interface: Cache

Gets an entry from the cache.

Specified by:

get in interface Cache<K,V>

Parameters:

key - the key whose associated value is to be returned

Returns:

the element, or null, if it does not exist.

put

public void put(K key,
                V value)

Description copied from interface: Cache

Associates the specified value with the specified key in the cache.

Specified by:

put in interface Cache<K,V>

Parameters:

key - key with which the specified value is to be associated

value - value to be associated with the specified key

remove

public void remove(K key)

Description copied from interface: Cache

Removes an entry from the cache.

Specified by:

remove in interface Cache<K,V>

Parameters:

key - key with which the specified value is to be associated.

clear

public void clear()

Description copied from interface: Cache

Clears the contents of the cache.

Specified by:

clear in interface Cache<K,V>

isEmpty

public boolean isEmpty()

Description copied from interface: Cache

Returns true if this cache contains no key-value mappings.

Specified by:

isEmpty in interface Cache<K,V>

keySet

public Set<K> keySet()

Description copied from interface: Cache

Returns a Set view of the keys contained in this cache.

Specified by:

keySet in interface Cache<K,V>

size

public int size()

Specified by:

size in interface Cache<K,V>

Returns:

the current size of the cache

removeAll

protected void removeAll(K key)

Removes all instances of the given key within the keys queue.