@Override default CompletableFuture<Integer> sumInt(final ToIntFunction<? super T> fn){
  return CompletableFuture.supplyAsync(null,getExec());
}

@ Override default CompletableFuture < Integer > sumInt ( final ToIntFunction < ? super T > fn ) { return CompletableFuture . supplyAsync ( null , getExec ( ) ) ; }
perform an asynchronous sum operation
