freenet.support

Class LRUCache<Key extends java.lang.Comparable<Key>,Value>

java.lang.Object

freenet.support.LRUCache<Key,Value>

public final class LRUCache<Key extends java.lang.Comparable<Key>,Value>
extends java.lang.Object

A key-value cache with a fixed size and optional expiration time. The least recently used item is removed if the cache is full and a new entry is added. Existing entries are only returned if they are not expired. Notice that expired items are ONLY removed when trying to get() them or when they fall out during push() because they are the least-recently-used. Therefore, this cache is intended for small sizes (or large amounts of small items). If you want to do a large cache and therefore need periodical garbage collection, please email me and I might implement it. Pushing and getting are executed in O(lg N) using a tree, to avoid hash collision DoS'es.

Constructor Summary

Constructors

Constructor and Description
LRUCache(int sizeLimit) Creates a cache without an expiration time.
LRUCache(int sizeLimit, long expirationDelay)

Method Summary

Modifier and Type	Method and Description
void	clear()
Value	get(Key key) Gets a value from the cache and moves it to top.
void	put(Key key, Value value) Puts a value in the cache.

Methods inherited from class java.lang.Object

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

Constructor Detail

LRUCache

public LRUCache(int sizeLimit)

Creates a cache without an expiration time.

Parameters:

sizeLimit - The maximal amount of items which the cache should hold.

LRUCache

public LRUCache(int sizeLimit,
                long expirationDelay)

Parameters:

sizeLimit - The maximal amount of items which the cache should hold.

expirationDelay - The amount of milliseconds after which an entry expires.

Method Detail

put

public void put(Key key,
                Value value)

Puts a value in the cache. If an entry for the key already exists, its value is updated and its expiration time is increased. If the size limit of this cache is exceeded the least recently used entry is removed.

get

public Value get(Key key)

Gets a value from the cache and moves it to top. Returns null if there is no entry for the given key or if the entry is expired. If an expired entry was found, it is removed from the cache.

clear

public void clear()