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