@GwtCompatible public interface Cache<K,V>
get(Object, Callable)
or put(Object, Object)
, and are stored in the cache until
either evicted or manually invalidated. The common way to build instances is using
CacheBuilder
.
Implementations of this interface are expected to be thread-safe, and can be safely accessed by multiple concurrent threads.
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> loader)
Returns the value associated with
key in this cache, obtaining that value from loader 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, or a set of default values if
the cache is not recording statistics.
|
@Nullable V getIfPresent(Object key)
key
in this cache, or null
if there is no
cached value for key
.V get(K key, Callable<? extends V> loader) throws ExecutionException
key
in this cache, obtaining that value from loader
if necessary. The method improves upon the conventional "if cached, return; otherwise
create, cache and return" pattern. For further improvements, use LoadingCache
and its
get(K)
method instead of this one.
Among the improvements that this method and LoadingCache.get(K)
both provide are:
Among the further improvements that LoadingCache
can provide but this method cannot:
Warning: For any given key, every loader
used with it should compute the same
value. Otherwise, a call that passes one loader
may return the result of another call
with a differently behaving loader
. For example, a call that requests a short timeout
for an RPC may wait for a similar call that requests a long timeout, or a call by an
unprivileged user may return a resource accessible only to a privileged user making a similar
call. To prevent this problem, create a key object that includes all values that affect the
result of the query. Or use LoadingCache.get(K)
, which lacks the ability to refer to
state other than that in the key.
Warning: as with CacheLoader.load(K)
, loader
must not return
null
; it may either return a non-null value or throw an exception.
No observable state associated with this cache is modified until loading completes.
ExecutionException
- if a checked exception was thrown while loading the valueUncheckedExecutionException
- if an unchecked exception was thrown while loading the
valueExecutionError
- if an error was thrown while loading the valueImmutableMap<K,V> getAllPresent(Iterable<?> keys)
keys
in this cache. The returned map will
only contain entries which are already present in the cache.void put(K key, V value)
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.
void putAll(Map<? extends K,? extends V> m)
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.void invalidate(Object key)
key
.void invalidateAll(Iterable<?> keys)
keys
.void invalidateAll()
long size()
CacheStats stats()
Warning: this cache may not be recording statistical data. For example, a cache
created using CacheBuilder
only does so if the CacheBuilder.recordStats()
method
was called. If statistics are not being recorded, a CacheStats
instance with zero for
all values is returned.
ConcurrentMap<K,V> asMap()
Iterators from the returned map are at least weakly consistent: they are safe for concurrent use, but if the cache is modified (including by eviction) after the iterator is created, it is undefined which of the changes (if any) will be reflected in that iterator.
void cleanUp()
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