Package ru.progrm_jarvis.javacommons.util.stream

Class AutoEnumCollectors

java.lang.Object

ru.progrm_jarvis.javacommons.util.stream.AutoEnumCollectors

public final class AutoEnumCollectors
extends Object

Collectors for use with enums with automatic type inference. This delegates its logic to the corresponding methods of EnumCollectors but infers enum types via type hints this leads to insignificant overhead due to empty-array allocation cost thus it is recommended to provide types explicitly in critical sections.

Method Summary

Modifier and Type	Method	Description
static <E extends Enum<E>, V> @NotNull Collector<E,?,@NotNull Map<E,V>>	toEnumMap(@NonNull Function<E,V> valueMapper, @NonNull BinaryOperator<V> merger, @Nullable E @NonNull ... typeHint)	Returns a Collector that accumulates the input elements into a new enum-Map.
static <T, E extends Enum<E>, V> @NotNull Collector<T,?,@NotNull Map<E,V>>	toEnumMap(@NonNull Function<T,E> keyMapper, @NonNull Function<T,V> valueMapper, @NonNull BinaryOperator<V> merger, @Nullable E @NonNull ... typeHint)	Returns a Collector that accumulates the input elements into a new enum-Map.
static <E extends Enum<E>> Collector<E,?,Set<E>>	toEnumSet(@Nullable E @NonNull ... typeHint)	Returns a Collector that accumulates the input elements into a new enum-Set.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

toEnumMap

@SafeVarargs
@NotNull
public static <T,
E extends Enum<E>,
V>
@NotNull Collector<T,?,@NotNull Map<E,V>> toEnumMap(@NonNull
 @NonNull Function<T,E> keyMapper,
 @NonNull
 @NonNull Function<T,V> valueMapper,
 @NonNull
 @NonNull BinaryOperator<V> merger,
 @Nullable
 @Nullable E @NonNull ... typeHint)

Returns a Collector that accumulates the input elements into a new enum-Map.

Type Parameters:

T - type of the input elements

E - type of the enum

V - type of map values

Parameters:

keyMapper - mapping function used to convert the elements into enum-keys

valueMapper - mapping function used to convert the elements into values

merger - function used to handle duplicate values

typeHint - array used for enum-type discovery

Returns:

a collector collecting al its elements into an enum-map

toEnumMap

@SafeVarargs
@NotNull
public static <E extends Enum<E>,
V>
@NotNull Collector<E,?,@NotNull Map<E,V>> toEnumMap(@NonNull
 @NonNull Function<E,V> valueMapper,
 @NonNull
 @NonNull BinaryOperator<V> merger,
 @Nullable
 @Nullable E @NonNull ... typeHint)

Returns a Collector that accumulates the input elements into a new enum-Map.

Type Parameters:

E - type of the enum

V - type of map values

Parameters:

valueMapper - mapping function used to convert the elements into values

merger - function used to handle duplicate values

typeHint - array used for enum-type discovery

Returns:

a collector collecting al its elements into an enum-map

toEnumSet

@SafeVarargs
public static <E extends Enum<E>>
Collector<E,?,Set<E>> toEnumSet(@Nullable
 @Nullable E @NonNull ... typeHint)

Returns a Collector that accumulates the input elements into a new enum-Set.

Type Parameters:

E - type of the enum

Parameters:

typeHint - array used for enum-type discovery

Returns:

a collector collecting al its elements into an enum-set