Java Stream - 如何map获取子字符串并转换为int，然后获取最大值

import java.util.stream.Stream;

public class Main {

  public static void main(String[] args) throws Exception {
    Stream.of("a1", "a2", "a3")
    .map(s -> s.substring(1))
    .mapToInt(Integer::parseInt)
    .max()
    .ifPresent(System.out::println);
  }

}