Class Cache<K,V>

java.lang.Object

nl.colorize.util.Cache<K,V>

public class Cache<K,V>
extends Object

Data structure for key/value pairs, where the value for each key is based on an underlying compute function. The cache is lazy: values are only computed when first requested. If the cache capacity has been exceeded, the oldest values are removed. Note that "oldest" means the values that were least recently *calculated*, not the values that were least recently *accessed*.

Instances of this class are thread-safe, it is safe to access the cache from different threads.

Method Summary

Modifier and Type	Method	Description
static <K,V> Cache<K,V>	from(Function<K,V> computeFunction)	Creates a lookup table based on the specified function.
static <K,V> Cache<K,V>	from(Function<K,V> computeFunction, int capacity)	Creates a lookup table based on the specified function.
V	get(K key)	Returns the value mapped to the specified key.
void	invalidate()	Forgets all cached key/value pairs in this cache.
void	invalidate(K key)	Forgets a cached key/value pairs in this cache.
protected boolean	isCached(K key)	Returns true if the value for the specified key is currently cached, and false if the value still needs to be computed.
void	precompute(Iterable<K> keys)	Precomputes the values for the specified keys, so the cached values are used when the key/value pairs are retrieved at a later time.
void	precompute(K key)	Precomputes the value for the specified key, so the cached value is used when the key/value pair is retrieved at a later time.
String	toString()

Methods inherited from class Object

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

Method Details

get

public V get(K key)

Returns the value mapped to the specified key. If the key/value pair is currently present in the cache, the cached value will be returned. Otherwise, the underlying function is used to compute the value, cache it, then return it.

precompute

public void precompute(K key)

Precomputes the value for the specified key, so the cached value is used when the key/value pair is retrieved at a later time.

precompute

public void precompute(Iterable<K> keys)

Precomputes the values for the specified keys, so the cached values are used when the key/value pairs are retrieved at a later time.

invalidate

public void invalidate(K key)

Forgets a cached key/value pairs in this cache. If the key/value pair was not yet computed this method does nothing.

invalidate

public void invalidate()

Forgets all cached key/value pairs in this cache.

isCached

protected boolean isCached(K key)

Returns true if the value for the specified key is currently cached, and false if the value still needs to be computed.

toString

public String toString()

Overrides:

toString in class Object

from

public static <K,V> Cache<K,V> from(Function<K,V> computeFunction)

Creates a lookup table based on the specified function. The lookup table will have unlimited capacity, cached values will never be removed.

from

public static <K,V> Cache<K,V> from(Function<K,V> computeFunction,
 int capacity)

Creates a lookup table based on the specified function. The lookup table will have limited capacity. If the number of key/value pairs exceeds the capacity, the oldest values will be removed.