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

Interface Policy.FixedExpiration<K,​V>

  • Enclosing interface:
    Policy<K,​V>
    public static interface Policy.FixedExpiration<K,​V>
    The low-level operations for a cache with a fixed expiration policy.

    • Method Summary

      All Methods Instance Methods Abstract Methods Default Methods 
      Modifier and Type Method Description
      default Optional<Duration> ageOf​(K key)
      Returns the age of the entry based on the expiration policy.
      OptionalLong ageOf​(K key, TimeUnit unit)
      Returns the age of the entry based on the expiration policy.
      default Duration getExpiresAfter()
      Returns the fixed duration used to determine if an entry should be automatically removed due to elapsing this time bound.
      @org.checkerframework.checker.index.qual.NonNegative long getExpiresAfter​(TimeUnit unit)
      Returns the fixed duration used to determine if an entry should be automatically removed due to elapsing this time bound.
      Map<K,​V> oldest​(@org.checkerframework.checker.index.qual.NonNegative int limit)
      Returns an unmodifiable snapshot Map view of the cache with ordered traversal.
      default <T> T oldest​(Function<Stream<Policy.CacheEntry<K,​V>>,​T> mappingFunction)
      Returns the computed result from the ordered traversal of the cache entries.
      void setExpiresAfter​(@org.checkerframework.checker.index.qual.NonNegative long duration, TimeUnit unit)
      Specifies that each entry should be automatically removed from the cache once a fixed duration has elapsed.
      default void setExpiresAfter​(Duration duration)
      Specifies that each entry should be automatically removed from the cache once a fixed duration has elapsed.
      Map<K,​V> youngest​(@org.checkerframework.checker.index.qual.NonNegative int limit)
      Returns an unmodifiable snapshot Map view of the cache with ordered traversal.
      default <T> T youngest​(Function<Stream<Policy.CacheEntry<K,​V>>,​T> mappingFunction)
      Returns the computed result from the ordered traversal of the cache entries.

    • Method Detail

      • ageOf

        OptionalLong ageOf​(K key,
                   TimeUnit unit)
        Returns the age of the entry based on the expiration policy. The entry's age is the cache's estimate of the amount of time since the entry's expiration was last reset.

        An expiration policy uses the age to determine if an entry is fresh or stale by comparing it to the freshness lifetime. This is calculated as fresh = freshnessLifetime > age where freshnessLifetime = expires - currentTime.

        Parameters:
        key - the key for the entry being queried
        unit - the unit that age is expressed in
        Returns:
        the age if the entry is present in the cache
        Throws:
        NullPointerException - if the specified key is null

      • ageOf

        default Optional<Duration> ageOf​(K key)
        Returns the age of the entry based on the expiration policy. The entry's age is the cache's estimate of the amount of time since the entry's expiration was last reset.

        An expiration policy uses the age to determine if an entry is fresh or stale by comparing it to the freshness lifetime. This is calculated as fresh = freshnessLifetime > age where freshnessLifetime = expires - currentTime.

        Parameters:
        key - the key for the entry being queried
        Returns:
        the age if the entry is present in the cache
        Throws:
        NullPointerException - if the specified key is null

      • getExpiresAfter

        @org.checkerframework.checker.index.qual.NonNegative long getExpiresAfter​(TimeUnit unit)
        Returns the fixed duration used to determine if an entry should be automatically removed due to elapsing this time bound. An entry is considered fresh if its age is less than this duration, and stale otherwise. The expiration policy determines when the entry's age is reset.
        Parameters:
        unit - the unit that duration is expressed in
        Returns:
        the length of time after which an entry should be automatically removed
        Throws:
        NullPointerException - if the unit is null

      • getExpiresAfter

        default Duration getExpiresAfter()
        Returns the fixed duration used to determine if an entry should be automatically removed due to elapsing this time bound. An entry is considered fresh if its age is less than this duration, and stale otherwise. The expiration policy determines when the entry's age is reset.
        Returns:
        the length of time after which an entry should be automatically removed

      • setExpiresAfter

        void setExpiresAfter​(@org.checkerframework.checker.index.qual.NonNegative long duration,
                     TimeUnit unit)
        Specifies that each entry should be automatically removed from the cache once a fixed duration has elapsed. The expiration policy determines when the entry's age is reset.
        Parameters:
        duration - the length of time after which an entry should be automatically removed
        unit - the unit that duration is expressed in
        Throws:
        IllegalArgumentException - if duration is negative
        NullPointerException - if the unit is null

      • setExpiresAfter

        default void setExpiresAfter​(Duration duration)
        Specifies that each entry should be automatically removed from the cache once a fixed duration has elapsed. The expiration policy determines when the entry's age is reset.
        Parameters:
        duration - the length of time after which an entry should be automatically removed
        Throws:
        IllegalArgumentException - if duration is negative
        NullPointerException - if the duration is null

      • oldest

        Map<K,​V> oldest​(@org.checkerframework.checker.index.qual.NonNegative int limit)
        Returns an unmodifiable snapshot Map view of the cache with ordered traversal. The order of iteration is from the entries most likely to expire (oldest) to the entries least likely to expire (youngest). This order is determined by the expiration policy's best guess at the time of creating this snapshot view.

        Beware that obtaining the mappings is NOT a constant-time operation. Because of the asynchronous nature of the page replacement policy, determining the retention ordering requires a traversal of the entries.

        Parameters:
        limit - the maximum size of the returned map (use Integer.MAX_VALUE to disregard the limit)
        Returns:
        a snapshot view of the cache from the oldest entry to the youngest

      • oldest

        default <T> T oldest​(Function<Stream<Policy.CacheEntry<K,​V>>,​T> mappingFunction)
        Returns the computed result from the ordered traversal of the cache entries. The oorder of iteration is from the entries most likely to expire (oldest) to the entries least likely to expire (youngest). This order is determined by the expiration policy's best guess at the time of creating this computation.

        Usage example: 

        
   List<K> tenOldestKeys = cache.policy().expireAfterWrite().orElseThrow()
       .oldest(stream -> stream.map(Map.Entry::getKey).limit(10).toList());

        Beware that this computation is performed within the eviction policy's exclusive lock, so the computation should be short and simple. While the computation is in progress further eviction maintenance will be halted.

        Type Parameters:
        T - the type of the result of the mappingFunction
        Parameters:
        mappingFunction - the mapping function to compute a value
        Returns:
        the computed value
        Throws:
        NullPointerException - if the mappingFunction is null
        RuntimeException - or Error if the mappingFunction does so

      • youngest

        Map<K,​V> youngest​(@org.checkerframework.checker.index.qual.NonNegative int limit)
        Returns an unmodifiable snapshot Map view of the cache with ordered traversal. The order of iteration is from the entries least likely to expire (youngest) to the entries most likely to expire (oldest). This order is determined by the expiration policy's best guess at the time of creating this snapshot view.

        Beware that obtaining the mappings is NOT a constant-time operation. Because of the asynchronous nature of the page replacement policy, determining the retention ordering requires a traversal of the entries.

        Parameters:
        limit - the maximum size of the returned map (use Integer.MAX_VALUE to disregard the limit)
        Returns:
        a snapshot view of the cache from the youngest entry to the oldest

      • youngest

        default <T> T youngest​(Function<Stream<Policy.CacheEntry<K,​V>>,​T> mappingFunction)
        Returns the computed result from the ordered traversal of the cache entries. The order of iteration is from the entries least likely to expire (youngest) to the entries most likely to expire (oldest). This order is determined by the expiration policy's best guess at the time of creating this computation.

        Usage example: 

        
   List<K> tenYoungestKeys = cache.policy().expireAfterWrite().orElseThrow()
       .youngest(stream -> stream.map(Map.Entry::getKey).limit(10).toList());

        Beware that this computation is performed within the eviction policy's exclusive lock, so the computation should be short and simple. While the computation is in progress further eviction maintenance will be halted.

        Type Parameters:
        T - the type of the result of the mappingFunction
        Parameters:
        mappingFunction - the mapping function to compute a value
        Returns:
        the computed value
        Throws:
        NullPointerException - if the mappingFunction is null
        RuntimeException - or Error if the mappingFunction does so