如何通过函数式编程来计算Java中的元音？

import java.util.Arrays;
import java.util.List;

public class VowelCount {
    public static void main(String[] args) {
        String input = "Hello World";
        long vowelCount = countVowels(input);
        System.out.println("Number of vowels: " + vowelCount);
    }

    private static long countVowels(String input) {
        List<Character> vowels = Arrays.asList('a', 'e', 'i', 'o', 'u');
        
        return input.chars()
                .mapToObj(ch -> (char) ch)
                .filter(ch -> vowels.contains(Character.toLowerCase(ch)))
                .count();
    }
}