question: public < V extends Comparable < ? super V > > OptionalLong minBy ( LongFunction < V > keyExtractor ) { ObjLongBox < V > result = collect ( null , null , null ) ; return result . a == null ? OptionalLong . empty ( ) : OptionalLong . of ( result . b ) ; }
target:  Returns the minimum element of this stream according to the provided key extractor function. <p> This is a terminal operation.