如何有效地转换List <T>？

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class ListConversion {
    public static void main(String[] args) {
        List<String> list1 = Arrays.asList("A", "B", "C");
        List<Integer> list2 = list1.stream()
                .map(String::length)
                .collect(Collectors.toList());
        System.out.println(list2);
    }
}

List<String> lowerCaseList = list1.stream()
        .map(String::toLowerCase)
        .collect(Collectors.toList());