Package org.agrona.collections

Class Int2ObjectCache<V>

java.lang.Object
org.agrona.collections.Int2ObjectCache<V>
Type Parameters:
V - type of values stored in the Map
All Implemented Interfaces:
Map<Integer,V>
public class Int2ObjectCache<V> extends Object implements Map<Integer,V>
A cache implementation specialised for int keys using open addressing to probe a set of fixed size.

The eviction strategy is to remove the oldest in a set if the key is not found, or if found then that item. The newly inserted item becomes the youngest in the set. Sets are evicted on a first in, first out, manner unless replacing a matching key.

A good set size would be in the range of 2 to 16 so that the references/keys can fit in a cache-line (assuming references are 32-bit references and 64-byte cache lines, YMMV). A linear search within a cache line is much less costly than a cache-miss to another line.

Null values are not supported by this cache.

  • Constructor Details

    • Int2ObjectCache

      public Int2ObjectCache(int numSets, int setSize, Consumer<V> evictionConsumer)
      Constructs cache with provided configuration.
      Parameters:
      numSets - number of sets, must be power or two.
      setSize - size of a single set, must be power or two.
      evictionConsumer - consumer to be notified when entry is being evicted from the cache.

  • Method Details

    • cacheHits

      public long cacheHits()
      The number of times a cache hit has occurred on the get(int) method.
      Returns:
      the number of times a cache hit has occurred on the get(int) method.

    • cacheMisses

      public long cacheMisses()
      The number of times a cache miss has occurred on the get(int) method.
      Returns:
      the number of times a cache miss has occurred on the get(int) method.

    • cachePuts

      public long cachePuts()
      The number of items that have been put in the cache.
      Returns:
      number of items that have been put in the cache.

    • resetCounters

      public void resetCounters()
      Reset the cache statistics counters to zero.

    • capacity

      public int capacity()
      Get the total capacity for the map to which the load factor will be a fraction of.
      Returns:
      the total capacity for the map.

    • size

      public int size()
      Specified by:
      size in interface Map<Integer,V>

    • isEmpty

      public boolean isEmpty()
      Specified by:
      isEmpty in interface Map<Integer,V>

    • containsKey

      public boolean containsKey(Object key)
      Specified by:
      containsKey in interface Map<Integer,V>

    • containsKey

      public boolean containsKey(int key)
      Overloaded version of Map.containsKey(Object) that takes a primitive int key.
      Parameters:
      key - for indexing the Map
      Returns:
      true if the key is found otherwise false.

    • containsValue

      public boolean containsValue(Object value)
      Specified by:
      containsValue in interface Map<Integer,V>

    • get

      public V get(Object key)
      Specified by:
      get in interface Map<Integer,V>

    • get

      public V get(int key)
      Overloaded version of Map.get(Object) that takes a primitive int key.
      Parameters:
      key - for indexing the Map
      Returns:
      the value if found otherwise null

    • getOrDefault

      public V getOrDefault(int key, V defaultValue)
      Returns the value to which the specified key is mapped, or defaultValue if this map contains no mapping for the key.
      Parameters:
      key - whose associated value is to be returned.
      defaultValue - the default mapping of the key.
      Returns:
      the value to which the specified key is mapped, or defaultValue if this map contains no mapping for the key.

    • forEach

      public void forEach(BiConsumer<? super Integer,? super V> action)
      Specified by:
      forEach in interface Map<Integer,V>

    • forEachInt

      public void forEachInt(IntObjConsumer<? super V> consumer)
      Implementation of the forEach(BiConsumer) that avoids boxing of keys.
      Parameters:
      consumer - to be called for each key/value pair.

    • computeIfAbsent

      public V computeIfAbsent(Integer key, Function<? super Integer,? extends V> mappingFunction)
      Specified by:
      computeIfAbsent in interface Map<Integer,V>

    • computeIfAbsent

      public V computeIfAbsent(int key, IntFunction<? extends V> mappingFunction)
      Get a value for a given key, or if it does ot exist then default the value via a IntFunction and put it in the cache.

      Primitive specialized version of Map.computeIfAbsent(K, java.util.function.Function<? super K, ? extends V>).

      Parameters:
      key - to search on.
      mappingFunction - to provide a value if the get returns null.
      Returns:
      the value if found otherwise the default.

    • computeIfPresent

      public V computeIfPresent(Integer key, BiFunction<? super Integer,? super V,? extends V> remappingFunction)
      Specified by:
      computeIfPresent in interface Map<Integer,V>

    • computeIfPresent

      public V computeIfPresent(int key, IntObjectToObjectFunction<? super V,? extends V> remappingFunction)
      If the value for the specified key is present attempts to compute a new mapping given the key and its current mapped value.

      Primitive specialized version of Map.computeIfPresent(Object, BiFunction).

      Parameters:
      key - with which the specified value is to be associated.
      remappingFunction - the function to compute a value.
      Returns:
      the new value associated with the specified key, or null if none.

    • compute

      public V compute(Integer key, BiFunction<? super Integer,? super V,? extends V> remappingFunction)
      Specified by:
      compute in interface Map<Integer,V>

    • compute

      public V compute(int key, IntObjectToObjectFunction<? super V,? extends V> remappingFunction)
      Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping).

      Primitive specialized version of Map.compute(Object, BiFunction).

      Parameters:
      key - with which the specified value is to be associated.
      remappingFunction - the function to compute a value.
      Returns:
      the new value associated with the specified key, or null if none.

    • merge

      public V merge(Integer key, V value, BiFunction<? super V,? super V,? extends V> remappingFunction)
      Specified by:
      merge in interface Map<Integer,V>

    • merge

      public V merge(int key, V value, BiFunction<? super V,? super V,? extends V> remappingFunction)
      If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value. Otherwise, replaces the associated value with the results of the given remapping function, or removes if the result is null.

      Primitive specialized version of Map.merge(Object, Object, BiFunction).

      Parameters:
      key - with which the resulting value is to be associated.
      value - the non-null value to be merged with the existing value associated with the key or, if no existing value or a null value is associated with the key, to be associated with the key.
      remappingFunction - the function to recompute a value if present.
      Returns:
      the new value associated with the specified key, or null if no value is associated with the key.

    • putIfAbsent

      public V putIfAbsent(Integer key, V value)
      Specified by:
      putIfAbsent in interface Map<Integer,V>

    • putIfAbsent

      public V putIfAbsent(int key, V value)
      If the specified key is not already associated with a value (or is mapped to null) associates it with the given value and returns null, else returns the current value.

      Primitive specialized version of Map.putIfAbsent(Object, Object).

      Parameters:
      key - with which the specified value is to be associated.
      value - to be associated with the specified key.
      Returns:
      the previous value associated with the specified key, or null if there was no mapping for the key.

    • put

      public V put(Integer key, V value)
      Specified by:
      put in interface Map<Integer,V>

    • put

      public V put(int key, V value)
      Overloaded version of Map.put(Object, Object) that takes a primitive int key.
      Parameters:
      key - for indexing the Map
      value - to be inserted in the Map
      Returns:
      always null (as per JCache API, as opposed to Map)

    • remove

      public boolean remove(Object key, Object value)
      Specified by:
      remove in interface Map<Integer,V>

    • remove

      public boolean remove(int key, V value)
      Removes the entry for the specified key only if it is currently mapped to the specified value.

      Primitive specialized version of Map.remove(Object, Object).

      Parameters:
      key - key with which the specified value is associated.
      value - expected to be associated with the specified key.
      Returns:
      true if the value was removed.

    • remove

      public V remove(Object key)
      Specified by:
      remove in interface Map<Integer,V>

    • remove

      public V remove(int key)
      Overloaded version of Map.remove(Object) that takes a primitive int key.
      Parameters:
      key - for indexing the Map
      Returns:
      the value if found otherwise null

    • replace

      public boolean replace(Integer key, V oldValue, V newValue)
      Specified by:
      replace in interface Map<Integer,V>

    • replace

      public boolean replace(int key, V oldValue, V newValue)
      Replaces the entry for the specified key only if currently mapped to the specified value.

      Primitive specialized version of Map.replace(Object, Object, Object).

      Parameters:
      key - with which the specified value is associated.
      oldValue - expected to be associated with the specified key.
      newValue - to be associated with the specified key.
      Returns:
      true if the value was replaced.

    • replace

      public V replace(Integer key, V value)
      Specified by:
      replace in interface Map<Integer,V>

    • replace

      public V replace(int key, V value)
      Replaces the entry for the specified key only if it is currently mapped to some value.

      Primitive specialized version of Map.replace(Object, Object).

      Parameters:
      key - with which the specified value is associated.
      value - to be associated with the specified key.
      Returns:
      the previous value associated with the specified key.

    • replaceAll

      public void replaceAll(BiFunction<? super Integer,? super V,? extends V> function)
      Specified by:
      replaceAll in interface Map<Integer,V>

    • replaceAllInt

      public void replaceAllInt(IntObjectToObjectFunction<? super V,? extends V> function)
      Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception.

      Primitive specialized version of Map.replaceAll(BiFunction).

      NB: Renamed from forEach to avoid overloading on parameter types of lambda expression, which doesn't play well with type inference in lambda expressions.

      Parameters:
      function - the function to apply to each entry.

    • clear

      public void clear()
      Clear down all items in the cache.

      If an exception occurs during the eviction function callback then clear may need to be called again to complete.

      If an exception occurs the cache should only be used when size() reports zero.

      Specified by:
      clear in interface Map<Integer,V>

    • putAll

      public void putAll(Map<? extends Integer,? extends V> map)
      Specified by:
      putAll in interface Map<Integer,V>

    • putAll

      public void putAll(Int2ObjectCache<? extends V> map)
      Put all values from the given map into this one without allocation.
      Parameters:
      map - whose value are to be added.

    • keySet

      public Int2ObjectCache<V>.KeySet keySet()
      Specified by:
      keySet in interface Map<Integer,V>

    • values

      public Int2ObjectCache<V>.ValueCollection values()
      Specified by:
      values in interface Map<Integer,V>

    • entrySet

      public Int2ObjectCache<V>.EntrySet entrySet()
      Specified by:
      entrySet in interface Map<Integer,V>

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • equals

      public boolean equals(Object o)
      Specified by:
      equals in interface Map<Integer,V>
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Specified by:
      hashCode in interface Map<Integer,V>
      Overrides:
      hashCode in class Object