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ForwardingCache (Guava: Google Core Libraries for Java 11.0.1 API)













    






    

    



    
  
    
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com.google.common.cache

    
Class ForwardingCache<K,V>
    

    java.lang.Object
  extended by com.google.common.collect.ForwardingObject
      extended by com.google.common.cache.ForwardingCache<K,V>

    

    

    All Implemented Interfaces: 
    Function<K,V>, Cache<K,V>
    

    

    

    Direct Known Subclasses: 
    ForwardingCache.SimpleForwardingCache, ForwardingLoadingCache
    

    

    

    

    @Beta
public abstract class ForwardingCache<K,V>
    extends ForwardingObject
    implements Cache<K,V>

    A cache which forwards all its method calls to another cache. Subclasses should override one or more methods to modify the behavior of the backing cache as desired per the decorator pattern.

    Since:
    10.0
    Author:
    Charles Fry

    Nested Class Summary
    static class ForwardingCache.SimpleForwardingCache<K,V>
              A simplified version of ForwardingCache where subclasses can pass in an already constructed Cache as the delegete.
     
    Constructor Summary
    protected ForwardingCache()
              Constructor for use by subclasses.
     
    Method Summary
     V apply(K key)
              Deprecated. 
     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.
    protected abstract  Cache<K,V> delegate()
              Returns the backing delegate instance that methods are forwarded to.
     V get(K key)
              Deprecated. 
     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<? extends K> keys)
              Returns a map of the values associated with keys in this cache.
     V getIfPresent(K key)
              Returns the value associated with key in this cache, or null if there is no cached value for key.
     V getUnchecked(K key)
              Deprecated. 
     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.
     long size()
              Returns the approximate number of entries in this cache.
     CacheStats stats()
              Returns a current snapshot of this cache's cumulative statistics.
     
    Methods inherited from class com.google.common.collect.ForwardingObject
    toString
     
    Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
     
    Methods inherited from interface com.google.common.base.Function
    equals
     

    Constructor Detail

    ForwardingCache

    protected ForwardingCache()
    Constructor for use by subclasses.

    Method Detail

    delegate

    protected abstract Cache<K,V> delegate()
    Description copied from class: ForwardingObject
    Returns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such as ForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.

    Specified by:
    delegate in class ForwardingObject

    getIfPresent

    @Nullable
public V getIfPresent(K key)
    Description copied from interface: Cache
    Returns the value associated with key in this cache, or null if there is no cached value for key.

    Specified by:
    getIfPresent in interface Cache<K,V>
    Since:
    11.0

    get

    public V get(K key,
             Callable<? extends V> valueLoader)
      throws ExecutionException
    Description copied from interface: Cache
    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.

    Specified by:
    get in interface Cache<K,V>
    Throws:
    ExecutionException - if a checked exception was thrown while loading the value
    Since:
    11.0

    getAllPresent

    public ImmutableMap<K,V> getAllPresent(Iterable<? extends K> keys)
    Description copied from interface: Cache
    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.

    Specified by:
    getAllPresent in interface Cache<K,V>
    Since:
    11.0

    put

    public void put(K key,
                V value)
    Description copied from interface: Cache
    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 Cache.get(Object, Callable) when using the conventional "if cached, return; otherwise create, cache and return" pattern.

    Specified by:
    put in interface Cache<K,V>
    Since:
    11.0

    invalidate

    public void invalidate(Object key)
    Description copied from interface: Cache
    Discards any cached value for key key.

    Specified by:
    invalidate in interface Cache<K,V>

    invalidateAll

    public void invalidateAll(Iterable<?> keys)
    Description copied from interface: Cache
    Discards any cached values for keys keys.

    Specified by:
    invalidateAll in interface Cache<K,V>
    Since:
    11.0

    invalidateAll

    public void invalidateAll()
    Description copied from interface: Cache
    Discards all entries in the cache.

    Specified by:
    invalidateAll in interface Cache<K,V>

    size

    public long size()
    Description copied from interface: Cache
    Returns the approximate number of entries in this cache.

    Specified by:
    size in interface Cache<K,V>

    stats

    public CacheStats stats()
    Description copied from interface: Cache
    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.

    Specified by:
    stats in interface Cache<K,V>

    asMap

    public ConcurrentMap<K,V> asMap()
    Description copied from interface: Cache
    Returns a view of the entries stored in this cache as a thread-safe map. Modifications made to the map directly affect the cache.

    Specified by:
    asMap in interface Cache<K,V>

    cleanUp

    public void cleanUp()
    Description copied from interface: Cache
    Performs any pending maintenance operations needed by the cache. Exactly which activities are performed -- if any -- is implementation-dependent.

    Specified by:
    cleanUp in interface Cache<K,V>

    get

    @Deprecated
public V get(K key)
      throws ExecutionException
    Deprecated. 

    Description copied from interface: Cache
    Returns the value associated with key in this cache, first loading that value if necessary. No observable state associated with this cache is modified until loading completes.

    Specified by:
    get in interface Cache<K,V>
    Throws:
    ExecutionException - if a checked exception was thrown while loading the value

    getUnchecked

    @Deprecated
public V getUnchecked(K key)
    Deprecated. 

    Description copied from interface: Cache
    Returns the value associated with key in this cache, first loading that value if necessary. No observable state associated with this cache is modified until computation completes. Unlike Cache.get(K, java.util.concurrent.Callable), this method does not throw a checked exception, and thus should only be used in situations where checked exceptions are not thrown by the cache loader.

    Warning: this method silently converts checked exceptions to unchecked exceptions, and should not be used with cache loaders which throw checked exceptions.

    Specified by:
    getUnchecked in interface Cache<K,V>

    apply

    @Deprecated
public V apply(K key)
    Deprecated. 

    Description copied from interface: Cache
    Discouraged. Provided to satisfy the Function interface; use Cache.get(K, java.util.concurrent.Callable) or Cache.getUnchecked(K) instead.

    Specified by:
    apply in interface Function<K,V>
    Specified by:
    apply in interface Cache<K,V>
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