Interface Cache<K,V>

Type Parameters:
K - the type of the cache's keys, which are not permitted to be null
V - the type of the cache's values, which are not permitted to be null
All Known Subinterfaces:
LoadingCache<K,V>
All Known Implementing Classes:
AbstractCache, AbstractLoadingCache, ForwardingCache, ForwardingCache.SimpleForwardingCache, ForwardingLoadingCache, ForwardingLoadingCache.SimpleForwardingLoadingCache
@DoNotMock("Use CacheBuilder.newBuilder().build()") @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. 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.

Since:
10.0
Author:
Charles Fry

  • Method Summary

    Modifier and Type
    Method
    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<? extends Object> keys)
    Returns a map of the values associated with keys in this cache.
    @Nullable 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<? extends Object> 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.

  • Method Details

    • getIfPresent

      @CanIgnoreReturnValue @Nullable V getIfPresent(@CompatibleWith("K") 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

      @CanIgnoreReturnValue V get(K key, Callable<? extends V> loader) throws ExecutionException
      Returns the value associated with 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.

      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<? extends Object> 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(@CompatibleWith("K") Object key)
      Discards any cached value for key key.

    • invalidateAll

      void invalidateAll(Iterable<? extends Object> 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, or a set of default values if the cache is not recording statistics. All statistics begin at zero and never decrease over the lifetime of the cache.

      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.

    • 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.

      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.

    • cleanUp

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