public < R > StreamEx < R > withFirst ( BiFunction < ? super T , ? super T , ? extends R > mapper ) { WithFirstSpliterator < T , R > spliterator = new WithFirstSpliterator <> ( spliterator ( ) , mapper ) ; return new StreamEx <> ( spliterator , context ) ; }
Returns a stream consisting of the results of applying the given function to the the first element and every other element of this stream .