com.google.common.cache

Interface Cache<K,V>

All Known Subinterfaces:

LoadingCache<K,V>

All Known Implementing Classes:

AbstractCache, AbstractLoadingCache, ForwardingCache, ForwardingCache.SimpleForwardingCache, ForwardingLoadingCache, ForwardingLoadingCache.SimpleForwardingLoadingCache

@Beta
@GwtCompatible
public interface Cache<K,V>

A semi-persistent mapping from keys to values. Cache entries are manually added using get(Object, Callable) or put(Object, Object), and are stored in the cache until either evicted or manually invalidated.

Implementations of this interface are expected to be thread-safe, and can be safely accessed by multiple concurrent threads.

Note that while this class is still annotated as Beta, the API is frozen from a consumer's standpoint. In other words existing methods are all considered non-Beta and won't be changed without going through an 18 month deprecation cycle; however new methods may be added at any time.

Since:

10.0

Author:

Charles Fry

Method Summary

Methods

Modifier and Type	Method and Description
ConcurrentMap<K,V>	asMap() Returns a view of the entries stored in this cache as a thread-safe map.
void	cleanUp() Performs any pending maintenance operations needed by the cache.
V	get(K key, Callable<? extends V> valueLoader) Returns the value associated with key in this cache, obtaining that value from valueLoader if necessary.
ImmutableMap<K,V>	getAllPresent(Iterable<?> keys) Returns a map of the values associated with keys in this cache.
V	getIfPresent(Object key) Returns the value associated with key in this cache, or null if there is no cached value for key.
void	invalidate(Object key) Discards any cached value for key key.
void	invalidateAll() Discards all entries in the cache.
void	invalidateAll(Iterable<?> keys) Discards any cached values for keys keys.
void	put(K key, V value) Associates value with key in this cache.
void	putAll(Map<? extends K,? extends V> m) Copies all of the mappings from the specified map to the cache.
long	size() Returns the approximate number of entries in this cache.
CacheStats	stats() Returns a current snapshot of this cache's cumulative statistics.

Method Detail

getIfPresent

@Nullable
V getIfPresent(Object key)

Returns the value associated with key in this cache, or null if there is no cached value for key.

Since:

11.0

get

V get(K key,
    Callable<? extends V> valueLoader)
      throws ExecutionException

Returns the value associated with key in this cache, obtaining that value from valueLoader if necessary. No observable state associated with this cache is modified until loading completes. This method provides a simple substitute for the conventional "if cached, return; otherwise create, cache and return" pattern.

Warning: as with CacheLoader.load(K), valueLoader must not return null; it may either return a non-null value or throw an exception.

Throws:

ExecutionException - if a checked exception was thrown while loading the value

UncheckedExecutionException - if an unchecked exception was thrown while loading the value

ExecutionError - if an error was thrown while loading the value

Since:

11.0

getAllPresent

ImmutableMap<K,V> getAllPresent(Iterable<?> keys)

Returns a map of the values associated with keys in this cache. The returned map will only contain entries which are already present in the cache.

Since:

11.0

put

void put(K key,
       V value)

Associates value with key in this cache. If the cache previously contained a value associated with key, the old value is replaced by value.

Prefer get(Object, Callable) when using the conventional "if cached, return; otherwise create, cache and return" pattern.

Since:

11.0

putAll

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

Copies all of the mappings from the specified map to the cache. The effect of this call is equivalent to that of calling put(k, v) on this map once for each mapping from key k to value v in the specified map. The behavior of this operation is undefined if the specified map is modified while the operation is in progress.

Since:

12.0

invalidate

void invalidate(Object key)

Discards any cached value for key key.

invalidateAll

void invalidateAll(Iterable<?> keys)

Discards any cached values for keys keys.

Since:

11.0

invalidateAll

void invalidateAll()

Discards all entries in the cache.

size

long size()

Returns the approximate number of entries in this cache.

stats

CacheStats stats()

Returns a current snapshot of this cache's cumulative statistics. All stats are initialized to zero, and are monotonically increasing over the lifetime of the cache.

asMap

ConcurrentMap<K,V> asMap()

Returns a view of the entries stored in this cache as a thread-safe map. Modifications made to the map directly affect the cache.

cleanUp

void cleanUp()

Performs any pending maintenance operations needed by the cache. Exactly which activities are performed -- if any -- is implementation-dependent.