Cache (Guava: Google Core Libraries for Java 20.0 API)

All Known Subinterfaces:

LoadingCache<K,V>

All Known Implementing Classes:

AbstractCache, AbstractLoadingCache, ForwardingCache, ForwardingCache.SimpleForwardingCache, ForwardingLoadingCache, ForwardingLoadingCache.SimpleForwardingLoadingCache
```
@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.
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

All Methods Instance Methods Abstract 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.
`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.

- Method Detail
  - getIfPresent
```
@Nullable
V getIfPresent(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
```
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:
    - awaiting the result of a pending load rather than starting a redundant one
    - eliminating the error-prone caching boilerplate
    - tracking load statistics
    Among the further improvements that LoadingCache can provide but this method cannot:
    - consolidation of the loader logic to a single authoritative location
    - refreshing of entries, including automated refreshing
    - bulk loading requests, including bulk loading implementations
    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<?> 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(Object key)
```
    Discards any cached value for key key.
  - invalidateAll
```
void invalidateAll(Iterable<?> 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.
    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.
  - cleanUp
```
void cleanUp()
```
    Performs any pending maintenance operations needed by the cache. Exactly which activities are performed -- if any -- is implementation-dependent.

Interface Cache<K,V>

Method Summary

Method Detail

getIfPresent

get

getAllPresent

put

putAll

invalidate

invalidateAll

invalidateAll

size

stats

asMap

cleanUp