Class Cache<K,​V>

  • Type Parameters:
    K - The type of the key of the cache
    V - The type of the values in the cache
    All Implemented Interfaces:
    Computable<K,​V>

    public class Cache<K,​V>
    extends java.lang.Object
    implements Computable<K,​V>
    Cache implementation that relies on FutureTask. Desired value will only be computed once and computed value stored in the cache. The implementation is based on an example from the "Java Concurrency in Practice" book authored by Brian Goetz and company.
    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static interface  Cache.CycleHandler<K>
      Should a cycle be detected during computation of a value for given key, this interface allows client code to register a callback that would get invoked in such a case.
      private class  Cache.OriginThreadAwareFuture
      Helper class, that remembers the future task origin thread, so that cycles could be detected.
    • Constructor Summary

      Constructors 
      Constructor Description
      Cache​(Computable<K,​V> computable)
      Create new cache with given computable to compute values.
      Cache​(Computable<K,​V> computable, Cache.CycleHandler<K> cycleHandler)
      Create new cache with given computable and cycle handler.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()
      Empty cache.
      V compute​(K key)
      Defines an expensive computation to retrieve value V from key K.
      boolean containsKey​(K key)
      Returns true if the key has already been cached.
      void remove​(K key)
      Remove item from the cache.
      int size()
      Returns the size of the cache
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Constructor Detail

      • Cache

        public Cache​(Computable<K,​V> computable)
        Create new cache with given computable to compute values. Detected cycles will be ignored as there is a no-op cycle handler registered by default.
        Parameters:
        computable -
      • Cache

        public Cache​(Computable<K,​V> computable,
                     Cache.CycleHandler<K> cycleHandler)
        Create new cache with given computable and cycle handler.
        Parameters:
        computable -
        cycleHandler -
    • Method Detail

      • compute

        public V compute​(K key)
        Description copied from interface: Computable
        Defines an expensive computation to retrieve value V from key K.
        Specified by:
        compute in interface Computable<K,​V>
        Parameters:
        key - input data.
        Returns:
        output from the computation.
      • clear

        public void clear()
        Empty cache.
      • containsKey

        public boolean containsKey​(K key)
        Returns true if the key has already been cached.
        Parameters:
        key -
        Returns:
        true if given key is present in the cache.
      • remove

        public void remove​(K key)
        Remove item from the cache.
        Parameters:
        key - item key.
      • size

        public int size()
        Returns the size of the cache
        Returns:
        The number of elements in the cache