tuwien.auto.calimero.buffer.cache
Class LFUCache

java.lang.Object
  tuwien.auto.calimero.buffer.cache.ExpiringCache
      tuwien.auto.calimero.buffer.cache.LFUCache

All Implemented Interfaces:

Cache

public class LFUCache
extends ExpiringCache

A Cache using a LFU replacement policy.

The usage value of CacheObject.getUsage() equals the access count, CacheObject.getCount().

Nested Class Summary

Nested classes/interfaces inherited from interface tuwien.auto.calimero.buffer.cache.Cache

Cache.Statistic

Field Summary

Fields inherited from class tuwien.auto.calimero.buffer.cache.ExpiringCache

defaultSweepInterval, map, sweepInterval

Constructor Summary

LFUCache(int cacheSize, int timeToExpire)
Creates a new LFU cache.

Method Summary

void	clear() Empties the cache of all CacheObjects.
CacheObject	get(java.lang.Object key) Gets the CacheObject associated with key from the cache.
protected void	notifyRemoved(CacheObject obj) Override this method to get notified when ExpiringCache.removeExpired() removed a CacheObject from the ExpiringCache.map.
void	put(CacheObject obj) Inserts the CacheObject obj into the cache.
void	remove(java.lang.Object key) Removes the CacheObject associated with key from the cache, if found.
Cache.Statistic	statistic() Returns information collected by this cache since its creation.

Methods inherited from class tuwien.auto.calimero.buffer.cache.ExpiringCache

removeExpired, startSweeper, stopSweeper

Methods inherited from class java.lang.Object

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

Constructor Detail

LFUCache

public LFUCache(int cacheSize,
                int timeToExpire)

Creates a new LFU cache.

Optionally, a maximum cache size and an expiring time can be specified.

Parameters:

cacheSize - maximum number of CacheObjects in the cache, or 0 for no maximum

timeToExpire - time in seconds for cache objects to stay valid, or 0 for no expiring

Method Detail

clear

public void clear()

Description copied from interface: Cache

Empties the cache of all CacheObjects.

get

public CacheObject get(java.lang.Object key)

Description copied from interface: Cache

Gets the CacheObject associated with key from the cache.

If found, the access count of the CacheObject is incremented by 1.

Parameters:

key - key to search

Returns:

the CacheObject or null if key does not exist in the cache

notifyRemoved

protected final void notifyRemoved(CacheObject obj)

Description copied from class: ExpiringCache

Override this method to get notified when ExpiringCache.removeExpired() removed a CacheObject from the ExpiringCache.map.

Overrides:

notifyRemoved in class ExpiringCache

Parameters:

obj - removed CacheObject

put

public void put(CacheObject obj)

Inserts the CacheObject obj into the cache.

If a CacheObject with an equal key (delivered by CacheObject.getKey()) to obj.getKey() is already in the cache, it will be replaced by obj.
CacheObject.resetTimestamp() is invoked on obj after obj was inserted successfully.
If expiring of cache objects is set, and the timestamp of a CacheObject is renewed after it has been put into the cache, a new put(CacheObject) is required for that object to apply the timestamp and keep the cache in a consistent state.

Parameters:

obj - CacheObject to put into the cache

remove

public void remove(java.lang.Object key)

Description copied from interface: Cache

Removes the CacheObject associated with key from the cache, if found.

Parameters:

key - key of CacheObject to remove

statistic

public Cache.Statistic statistic()

Description copied from interface: Cache

Returns information collected by this cache since its creation.

Returns:

a Cache.Statistic object