Package no.digipost.stream

Interface EmptyResultIfEmptySourceCollector<T,​A,​R>

  • Type Parameters:
    T - the type of input elements to the reduction operation
    R - the type of value contained in the resulting Optional, if not source is empty.
    All Superinterfaces:
    Collector<T,​A,​Optional<R>>
    All Known Implementing Classes:
    EnforceAtMostOneElementCollector
    public interface EmptyResultIfEmptySourceCollector<T,​A,​R>
extends Collector<T,​A,​Optional<R>>
    A collector type specific for implementations which produce an Optional based on if the source (typically a Stream, or more apropriately, a NonEmptyStream) yields no elements or any element(s). Typically appropriate for reduction operations which needs at least one element to produce a valid result.