@GwtCompatible public abstract class AbstractCache<K,V> extends Object implements Cache<K,V>
Cacheinterface to minimize the effort required to implement this interface.
To implement a cache, the programmer needs only to extend this class and provide an
implementation for the
put(K, V) and
implemented in terms of
putAll(java.util.Map<? extends K, ? extends V>) is implemented in terms of
invalidateAll(Iterable) is implemented in terms of
cleanUp() is a no-op. All other methods throw an
|Modifier and Type||Class and Description|
|Modifier||Constructor and Description|
Constructor for use by subclasses.
|Modifier and Type||Method and Description|
Returns a view of the entries stored in this cache as a thread-safe map.
Performs any pending maintenance operations needed by the cache.
Returns the value associated with
This implementation of
Discards any cached value for key
Discards all entries in the cache.
Discards any cached values for keys
Copies all of the mappings from the specified map to the cache.
Returns the approximate number of entries in this cache.
Returns a current snapshot of this cache's cumulative statistics, or a set of default values if the cache is not recording statistics.
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
keyin this cache, obtaining that value from
loaderif necessary. The method improves upon the conventional "if cached, return; otherwise create, cache and return" pattern. For further improvements, use
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
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.
public ImmutableMap<K,V> getAllPresent(Iterable<?> keys)
getAllPresentlacks any insight into the internal cache data structure, and is thus forced to return the query keys instead of the cached keys. This is only possible with an unsafe cast which requires
keysto actually be of type
K. Returns a map of the values associated with
keysin this cache. The returned map will only contain entries which are already present in the cache.
keyin this cache. If the cache previously contained a value associated with
key, the old value is replaced by
Cache.get(Object, Callable) when using the conventional "if cached, return;
otherwise create, cache and return" pattern.
put(k, v)on this map once for each mapping from key
vin the specified map. The behavior of this operation is undefined if the specified map is modified while the operation is in progress.
public void cleanUp()
public long size()
public void invalidate(Object key)
public void invalidateAll(Iterable<?> keys)
public void invalidateAll()
public CacheStats stats()
Warning: this cache may not be recording statistical data. For example, a cache
CacheBuilder only does so if the
was called. If statistics are not being recorded, a
CacheStats instance with zero for
all values is returned.
public 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.
Warning to users of Java 8+: do not call any of the new default methods that
have been newly added to
ConcurrentMap! These are marked with "Since: 1.8" in the
ConcurrentMap documentation. They will not function correctly and it is impossible for
Guava to fix them until Guava is ready to require Java 8 for all users.
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