Module com.github.benmanes.caffeine
Package com.github.benmanes.caffeine.cache

Interface Cache<K,​V>

  • Type Parameters:
    K - the type of keys maintained by this cache
    V - the type of mapped values
    All Known Subinterfaces:
    LoadingCache<K,​V>
    public interface Cache<K,​V>
    A semi-persistent mapping from keys to values. Cache entries are manually added using get(Object, Function) 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.

    • Method Summary

      All Methods Instance Methods Abstract Methods 
      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.
      @org.checkerframework.checker.index.qual.NonNegative long estimatedSize()
      Returns the approximate number of entries in this cache.
      @PolyNull V get​(K key, Function<? super K,​? extends @PolyNull V> mappingFunction)
      Returns the value associated with the key in this cache, obtaining that value from the mappingFunction if necessary.
      Map<K,​V> getAll​(Iterable<? extends K> keys, Function<? super Set<? extends K>,​? extends Map<? extends K,​? extends V>> mappingFunction)
      Returns a map of the values associated with the keys, creating or retrieving those values if necessary.
      Map<K,​V> getAllPresent​(Iterable<? extends K> keys)
      Returns a map of the values associated with the keys in this cache.
      @Nullable V getIfPresent​(K key)
      Returns the value associated with the key in this cache, or null if there is no cached value for the key.
      void invalidate​(K key)
      Discards any cached value for the key.
      void invalidateAll()
      Discards all entries in the cache.
      void invalidateAll​(Iterable<? extends K> keys)
      Discards any cached values for the keys.
      Policy<K,​V> policy()
      Returns access to inspect and perform low-level operations on this cache based on its runtime characteristics.
      void put​(K key, V value)
      Associates the value with the key in this cache.
      void putAll​(Map<? extends K,​? extends V> map)
      Copies all of the mappings from the specified map to the cache.
      CacheStats stats()
      Returns a current snapshot of this cache's cumulative statistics.

    • Method Detail

      • getIfPresent

        @Nullable V getIfPresent​(K key)
        Returns the value associated with the key in this cache, or null if there is no cached value for the key.
        Parameters:
        key - the key whose associated value is to be returned
        Returns:
        the value to which the specified key is mapped, or null if this cache contains no mapping for the key
        Throws:
        NullPointerException - if the specified key is null

      • get

        @PolyNull V get​(K key,
                Function<? super K,​? extends @PolyNull V> mappingFunction)
        Returns the value associated with the key in this cache, obtaining that value from the mappingFunction if necessary. This method provides a simple substitute for the conventional "if cached, return; otherwise create, cache and return" pattern.

        If the specified key is not already associated with a value, attempts to compute its value using the given mapping function and enters it into this cache unless null. The entire method invocation is performed atomically, so the function is applied at most once per key. Some attempted update operations on this cache by other threads may be blocked while the computation is in progress, so the computation should be short and simple, and must not attempt to update any other mappings of this cache.

        Warning: as with CacheLoader.load(K), mappingFunction must not attempt to update any other mappings of this cache.

        Parameters:
        key - the key with which the specified value is to be associated
        mappingFunction - the function to compute a value
        Returns:
        the current (existing or computed) value associated with the specified key, or null if the computed value is null
        Throws:
        NullPointerException - if the specified key or mappingFunction is null
        IllegalStateException - if the computation detectably attempts a recursive update to this cache that would otherwise never complete
        RuntimeException - or Error if the mappingFunction does so, in which case the mapping is left unestablished

      • getAllPresent

        Map<K,​V> getAllPresent​(Iterable<? extends K> keys)
        Returns a map of the values associated with the keys in this cache. The returned map will only contain entries which are already present in the cache.

        Note that duplicate elements in keys, as determined by Object.equals(java.lang.Object), will be ignored.

        Parameters:
        keys - the keys whose associated values are to be returned
        Returns:
        the unmodifiable mapping of keys to values for the specified keys found in this cache
        Throws:
        NullPointerException - if the specified collection is null or contains a null element

      • getAll

        Map<K,​V> getAll​(Iterable<? extends K> keys,
                      Function<? super Set<? extends K>,​? extends Map<? extends K,​? extends V>> mappingFunction)
        Returns a map of the values associated with the keys, creating or retrieving those values if necessary. The returned map contains entries that were already cached, combined with the newly loaded entries; it will never contain null keys or values.

        A single request to the mappingFunction is performed for all keys which are not already present in the cache. All entries returned by mappingFunction will be stored in the cache, over-writing any previously cached values. If another call to get(K, java.util.function.Function<? super K, ? extends V>) tries to load the value for a key in keys, implementations may either have that thread load the entry or simply wait for this thread to finish and return the loaded value. In the case of overlapping non-blocking loads, the last load to complete will replace the existing entry. Note that multiple threads can concurrently load values for distinct keys. Any loaded values for keys that were not specifically requested will not be returned, but will be stored in the cache.

        Note that duplicate elements in keys, as determined by Object.equals(java.lang.Object), will be ignored.

        Parameters:
        keys - the keys whose associated values are to be returned
        mappingFunction - the function to compute the values
        Returns:
        an unmodifiable mapping of keys to values for the specified keys in this cache
        Throws:
        NullPointerException - if the specified collection is null or contains a null element, or if the map returned by the mappingFunction is null
        RuntimeException - or Error if the mappingFunction does so, in which case the mapping is left unestablished

      • put

        void put​(K key,
         V value)
        Associates the value with the key in this cache. If the cache previously contained a value associated with the key, the old value is replaced by the new value.

        Prefer get(Object, Function) when using the conventional "if cached, return; otherwise create, cache and return" pattern.

        Parameters:
        key - the key with which the specified value is to be associated
        value - value to be associated with the specified key
        Throws:
        NullPointerException - if the specified key or value is null

      • putAll

        void putAll​(Map<? extends K,​? extends V> map)
        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.
        Parameters:
        map - the mappings to be stored in this cache
        Throws:
        NullPointerException - if the specified map is null or the specified map contains null keys or values

      • invalidate

        void invalidate​(K key)
        Discards any cached value for the key. The behavior of this operation is undefined for an entry that is being loaded (or reloaded) and is otherwise not present.
        Parameters:
        key - the key whose mapping is to be removed from the cache
        Throws:
        NullPointerException - if the specified key is null

      • invalidateAll

        void invalidateAll​(Iterable<? extends K> keys)
        Discards any cached values for the keys. The behavior of this operation is undefined for an entry that is being loaded (or reloaded) and is otherwise not present.
        Parameters:
        keys - the keys whose associated values are to be removed
        Throws:
        NullPointerException - if the specified collection is null or contains a null element

      • invalidateAll

        void invalidateAll()
        Discards all entries in the cache. The behavior of this operation is undefined for an entry that is being loaded (or reloaded) and is otherwise not present.

      • estimatedSize

        @CheckReturnValue
@org.checkerframework.checker.index.qual.NonNegative long estimatedSize()
        Returns the approximate number of entries in this cache. The value returned is an estimate; the actual count may differ if there are concurrent insertions or removals, or if some entries are pending removal due to expiration or weak/soft reference collection. In the case of stale entries this inaccuracy can be mitigated by performing a cleanUp() first.
        Returns:
        the estimated number of mappings

      • stats

        @CheckReturnValue
CacheStats stats()
        Returns a current snapshot of this cache's cumulative statistics. All statistics are initialized to zero, and are monotonically increasing over the lifetime of the cache.

        Due to the performance penalty of maintaining statistics, some implementations may not record the usage history immediately or at all.

        Returns:
        the current snapshot of the statistics of this cache

      • asMap

        @CheckReturnValue
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.

        A computation operation, such as ConcurrentMap.compute(K, java.util.function.BiFunction<? super K, ? super V, ? extends V>), performs the entire method invocation atomically, so the function is applied at most once per key. Some attempted update operations by other threads may be blocked while computation is in progress. The computation must not attempt to update any other mappings of this 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.

        Returns:
        a thread-safe view of this cache supporting all of the optional Map operations

      • cleanUp

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

      • policy

        @CheckReturnValue
Policy<K,​V> policy()
        Returns access to inspect and perform low-level operations on this cache based on its runtime characteristics. These operations are optional and dependent on how the cache was constructed and what abilities the implementation exposes.

        Warning: policy operations must not be performed from within an atomic scope of another cache operation.

        Returns:
        access to inspect and perform advanced operations based on the cache's characteristics