[Java] Class Weighers

public final class Weighers
extends Object

Method Detail

<K, V> public static EntryWeigher<K, V> asEntryWeigher(Weigher<? super V> weigher)

A entry weigher backed by the specified weigher. The weight of the value determines the weight of the entry.

Parameters:

weigher - the weigher to be "wrapped" in a entry weigher.

Returns:

A entry weigher view of the specified weigher.

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.

<E> @SuppressWarnings({"cast", "unchecked"}) public static 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.

Returns:

A weigher where each element takes one unit of capacity.

<K, V> @SuppressWarnings({"cast", "unchecked"}) public static 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.

Returns:

A weigher where a value takes one unit of capacity.

<E> @SuppressWarnings({"cast", "unchecked"}) public static 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.

Returns:

A weigher where each element takes one unit of capacity.

<E> @SuppressWarnings({"cast", "unchecked"}) public static 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.

Returns:

A weigher where each element takes one unit of capacity.

<A, B> @SuppressWarnings({"cast", "unchecked"}) public static 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.

Returns:

A weigher where each entry takes one unit of capacity.

<E> @SuppressWarnings({"cast", "unchecked"}) public static 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.

Returns:

A weigher where each element takes one unit of capacity.

<V> @SuppressWarnings({"cast", "unchecked"}) public static 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.

Returns:

A weigher where a value takes one unit of capacity.