Package io.micronaut.core.util.clhm

Class Weighers

java.lang.Object
io.micronaut.core.util.clhm.Weighers
public final class Weighers extends Object
A common set of Weigher and EntryWeigher implementations.
Author:
ben.manes@gmail.com (Ben Manes)
See Also:

  • Method Details

    • asEntryWeigher

      public static <K, V> EntryWeigher<K,V> asEntryWeigher(Weigher<? super V> weigher)
      An entry weigher backed by the specified weigher. The weight of the value determines the weight of the entry.
      Type Parameters:
      K - The key type
      V - The value type
      Parameters:
      weigher - the weigher to be "wrapped" in an entry weigher.
      Returns:
      An entry weigher view of the specified weigher.

    • entrySingleton

      public static <K, V> EntryWeigher<K,V> entrySingleton()
      A weigher where an entry has a weight of 1. A map bounded with this weigher will evict when the number of key-value pairs exceeds the capacity.
      Type Parameters:
      K - The key type
      V - The value type
      Returns:
      A weigher where a value takes one unit of capacity.

    • singleton

      public static <V> Weigher<V> singleton()
      A weigher where a value has a weight of 1. A map bounded with this weigher will evict when the number of key-value pairs exceeds the capacity.
      Type Parameters:
      V - The value type
      Returns:
      A weigher where a value takes one unit of capacity.

    • byteArray

      public static Weigher<byte[]> byteArray()
      A weigher where the value is a byte array and its weight is the number of bytes. A map bounded with this weigher will evict when the number of bytes exceeds the capacity rather than the number of key-value pairs in the map. This allows for restricting the capacity based on the memory-consumption and is primarily for usage by dedicated caching servers that hold the serialized data.

      A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

      Returns:
      A weigher where each byte takes one unit of capacity.

    • iterable

      public static <E> Weigher<? super Iterable<E>> iterable()
      A weigher where the value is a Iterable and its weight is the number of elements. This weigher only should be used when the alternative collection() weigher cannot be, as evaluation takes O(n) time. A map bounded with this weigher will evict when the total number of elements exceeds the capacity rather than the number of key-value pairs in the map.

      A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

      Type Parameters:
      E - The element type
      Returns:
      A weigher where each element takes one unit of capacity.

    • collection

      public static <E> Weigher<? super Collection<E>> collection()
      A weigher where the value is a Collection and its weight is the number of elements. A map bounded with this weigher will evict when the total number of elements exceeds the capacity rather than the number of key-value pairs in the map.

      A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

      Type Parameters:
      E - The element type
      Returns:
      A weigher where each element takes one unit of capacity.

    • list

      public static <E> Weigher<? super List<E>> list()
      A weigher where the value is a List and its weight is the number of elements. A map bounded with this weigher will evict when the total number of elements exceeds the capacity rather than the number of key-value pairs in the map.

      A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

      Type Parameters:
      E - The element type
      Returns:
      A weigher where each element takes one unit of capacity.

    • set

      public static <E> Weigher<? super Set<E>> set()
      A weigher where the value is a Set and its weight is the number of elements. A map bounded with this weigher will evict when the total number of elements exceeds the capacity rather than the number of key-value pairs in the map.

      A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

      Type Parameters:
      E - The element type
      Returns:
      A weigher where each element takes one unit of capacity.

    • map

      public static <A, B> Weigher<? super Map<A,B>> map()
      A weigher where the value is a Map and its weight is the number of entries. A map bounded with this weigher will evict when the total number of entries across all values exceeds the capacity rather than the number of key-value pairs in the map.

      A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

      Type Parameters:
      A - The key type
      B - The value type
      Returns:
      A weigher where each entry takes one unit of capacity.