Java Stream - 如何map从int数组创建新值

import java.util.Arrays;

public class Main {

  public static void main(String[] args) throws Exception {
    Arrays.stream(new int[] {1, 2, 3})
    .map(n -> 2 * n + 1)
    .average()
    .ifPresent(System.out::println);
  }

}