Java Stream - 如何将double映射为int，然后映射到Object

import java.util.stream.Stream;

public class Main {

  public static void main(String[] args) throws Exception {
    Stream.of(1.0, 2.0, 3.0)
    .mapToInt(Double::intValue)
    .mapToObj(i -> "a" + i)
    .forEach(System.out::println);

  }

}