Class Selectables

java.lang.Object

org.microbean.assign.Selectables

public final class Selectables
extends Object

Utility methods for working with Selectables.

Author:

Laird Nelson

See Also:

• Selectable

Method Summary

Modifier and Type	Method	Description
static <C,E> Selectable<C,E>	caching(Selectable<? super C, E> selectable)	Returns a Selectable that caches its results.
static <C,E> Selectable<C,E>	caching(Selectable<? super C, E> selectable, BiFunction<? super C, Function<? super C, ? extends List<E>>, ? extends List<E>> f)	Returns a Selectable that caches its results.
static <C extends AnnotatedConstruct, E> Selectable<C,E>	convert(Selectable<? super Annotated<C>, E> s)	Deprecated, for removal: This API element is subject to removal in a future version.
static <C extends AnnotatedConstruct, E> Selectable<C,E>	convert(Selectable<? super Annotated<C>, E> s, Predicate<? super ExecutableElement> annotationElementInclusionPredicate)	Deprecated, for removal: This API element is subject to removal in a future version.
static final <C,E> Selectable<C,E>	empty()	Returns a Selectable whose Selectable.select(Object) method always returns an empty, immutable List.
static <C,E> Selectable<C,E>	filtering(Collection<? extends E> collection, BiPredicate<? super E, ? super C> p)	Returns a Selectable using the supplied Collection as its elements, and the supplied BiPredicate as its selector.

Methods inherited from class Object

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

Method Details

caching

public static <C,E> Selectable<C,E> caching(Selectable<? super C, E> selectable)

Returns a Selectable that caches its results.

The cache is unbounded.

Type Parameters:

C - the criteria type

E - the element type

Parameters:

selectable - a Selectable; must not be null

Returns:

a non-null Selectable

Throws:

NullPointerException - if selectable is null

See Also:

• caching(Selectable, BiFunction)

caching

public static <C,E> Selectable<C,E> caching(Selectable<? super C, E> selectable,
 BiFunction<? super C, Function<? super C, ? extends List<E>>, ? extends List<E>> f)

Returns a Selectable that caches its results.

Type Parameters:

C - the criteria type

E - the element type

Parameters:

selectable - a Selectable; must not be null

f - a BiFunction that returns a cached result, computing it on demand via its supplied mapping Function if necessary; must not be null; normally safe for concurrent use by multiple threads; often a reference to the ConcurrentHashMap.computeIfAbsent(Object, Function) method

Returns:

a non-null Selectable

Throws:

NullPointerException - if selectable or f is null

See Also:

• ConcurrentHashMap.computeIfAbsent(Object, Function)

convert

@Deprecated(forRemoval=true)
public static <C extends AnnotatedConstruct, E>
Selectable<C,E> convert(Selectable<? super Annotated<C>, E> s)

Deprecated, for removal: This API element is subject to removal in a future version.

An experimental method that converts a Selectable accepting Annotated<AnnotatedConstruct> instances into a Selectable accepting AnnotatedConstruct instances.

Type Parameters:

C - the criteria type

E - the element type

Parameters:

s - a non-null Selectable accepting Annotated<AnnotatedConstruct> instances

Returns:

a non-null, determinate Selectable accepting AnnotatedConstruct instances

Throws:

NullPointerException - if s is null

See Also:

• convert(Selectable, Predicate)
• Annotated
• AnnotatedConstruct

convert

@Deprecated(forRemoval=true)
public static <C extends AnnotatedConstruct, E>
Selectable<C,E> convert(Selectable<? super Annotated<C>, E> s,
 Predicate<? super ExecutableElement> annotationElementInclusionPredicate)

Deprecated, for removal: This API element is subject to removal in a future version.

An experimental method that converts a Selectable accepting Annotated<AnnotatedConstruct> instances into a Selectable accepting AnnotatedConstruct instances.

Type Parameters:

C - the criteria type

E - the element type

Parameters:

s - a non-null Selectable accepting Annotated<AnnotatedConstruct> instances

annotationElementInclusionPredicate - a Predicate that returns true if a given ExecutableElement, representing an annotation element, is to be included in comparison operations; may be null in which case it is as if e -> true were supplied instead

Returns:

a non-null, determinate Selectable accepting AnnotatedConstruct instances

Throws:

NullPointerException - if s is null

See Also:

• Annotated
• Annotated.of(AnnotatedConstruct, Predicate)
• AnnotatedConstruct

empty

public static final <C,E> Selectable<C,E> empty()

Returns a Selectable whose Selectable.select(Object) method always returns an empty, immutable List.

This method is useful primarily for completeness and for testing pathological situations.

Type Parameters:

C - the criteria type

E - the element type

Returns:

a non-null Selectable

filtering

public static <C,E> Selectable<C,E> filtering(Collection<? extends E> collection,
 BiPredicate<? super E, ? super C> p)

Returns a Selectable using the supplied Collection as its elements, and the supplied BiPredicate as its selector.

There is no guarantee that this method will return new Selectable instances.

The Selectable instances returned by this method may or may not cache their selections.

The selector tests its first argument to see if it is selected by its second argument. The selector is invoked repeatedly. If, for any given invocation, the first argument is selected, the selected element is added to the selection that is eventually returned as a sublist of the supplied Collection. The selector must additionally be idempotent and must produce a determinate value when given the same arguments.

No validation of these semantics of the selector is performed.

Type Parameters:

C - the criteria type

E - the element type

Parameters:

collection - a Collection of elements from which sublists may be selected; must not be null

p - the selector; must not be null

Returns:

a Selectable; never null

Throws:

NullPointerException - if either collection or p is null