ForwardingCache (Guava: Google Core Libraries for Java 19.0 API)

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

All Implemented Interfaces:

Cache<K,V>

Direct Known Subclasses:

ForwardingCache.SimpleForwardingCache, ForwardingLoadingCache
```
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

Nested Classes
Modifier and Type	Class and Description
`static class`	`ForwardingCache.SimpleForwardingCache<K,V>` A simplified version of `ForwardingCache` where subclasses can pass in an already constructed `Cache` as the delegate.

Constructor Summary

Constructors
Modifier Constructor and Description

protected ForwardingCache()
Constructor for use by subclasses.

Constructors
Modifier	Constructor and Description
`protected`	`ForwardingCache()` Constructor for use by subclasses.

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.
`protected abstract Cache<K,V>`	`delegate()` Returns the backing delegate instance that methods are forwarded to.
`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.

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

- 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(Object 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<?> 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
  - putAll
```
public void putAll(Map<? extends K,? extends V> m)
```
    Description copied from interface: Cache
    
    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.
    
    Specified by:
    
    putAll in interface Cache<K,V>
    
    Since:
    
    12.0
  - 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.
    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.
    
    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>

Class ForwardingCache<K,V>

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class com.google.common.collect.ForwardingObject

Methods inherited from class java.lang.Object

Constructor Detail

ForwardingCache

Method Detail

delegate

getIfPresent

get

getAllPresent

put

putAll

invalidate

invalidateAll

invalidateAll

size

stats

asMap

cleanUp