如何在Java中通过任意数字组创建笛卡尔积？

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

public class CartesianProduct {
    public static void main(String[] args) {
        List<List<Integer>> input = new ArrayList<>();
        input.add(Arrays.asList(1, 2, 3));
        input.add(Arrays.asList(4, 5));
        input.add(Arrays.asList(6, 7, 8, 9));

        List<List<Integer>> cartesianProduct = cartesianProduct(input);
        System.out.println(cartesianProduct);
    }

    public static List<List<Integer>> cartesianProduct(List<List<Integer>> inputLists) {
        if (inputLists.size() == 0) {
            List<List<Integer>> result = new ArrayList<>();
            result.add(new ArrayList<>());
            return result;
        } else {
            List<List<Integer>> smallerCartesianProduct = cartesianProduct(inputLists.subList(1, inputLists.size()));
            List<List<Integer>> result = new ArrayList<>();

            for (List<Integer> list : smallerCartesianProduct) {
                for (Integer item : inputLists.get(0)) {
                    List<Integer> newList = new ArrayList<>(list);
                    newList.add(item);
                    result.add(newList);
                }
            }

            return result;
        }
    }
}