public <V extends Comparable<? super V>>OptionalDouble maxBy(DoubleFunction<V> keyExtractor){
  ObjDoubleBox<V> result=collect(null,null,null);
  return result.a == null ? OptionalDouble.empty() : OptionalDouble.of(result.b);
}

public < V extends Comparable < ? super V > > OptionalDouble maxBy ( DoubleFunction < V > keyExtractor ) { ObjDoubleBox < V > result = collect ( null , null , null ) ; return result . a == null ? OptionalDouble . empty ( ) : OptionalDouble . of ( result . b ) ; }
returns the maximum element of this stream according to the provided key extractor function . < p > this is a terminal operation .
