在Java中如何将powerSet的内容保存到二维数组中

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

public class PowerSet {
    public static void main(String[] args) {
        int[] nums = {1, 2, 3};
        List<List<Integer>> powerSet = generatePowerSet(nums);
        int[][] powerSetArray = convertTo2DArray(powerSet);
        printArray(powerSetArray);
    }

    public static List<List<Integer>> generatePowerSet(int[] nums) {
        List<List<Integer>> powerSet = new ArrayList<>();
        backtrack(nums, 0, new ArrayList<>(), powerSet);
        return powerSet;
    }

    private static void backtrack(int[] nums, int start, List<Integer> subset, List<List<Integer>> powerSet) {
        powerSet.add(new ArrayList<>(subset));
        for (int i = start; i < nums.length; i++) {
            subset.add(nums[i]);
            backtrack(nums, i + 1, subset, powerSet);
            subset.remove(subset.size() - 1);
        }
    }

    public static int[][] convertTo2DArray(List<List<Integer>> powerSet) {
        int[][] powerSetArray = new int[powerSet.size()][];
        for (int i = 0; i < powerSet.size(); i++) {
            List<Integer> subset = powerSet.get(i);
            powerSetArray[i] = new int[subset.size()];
            for (int j = 0; j < subset.size(); j++) {
                powerSetArray[i][j] = subset.get(j);
            }
        }
        return powerSetArray;
    }

    public static void printArray(int[][] array) {
        for (int[] row : array) {
            for (int num : row) {
                System.out.print(num + " ");
            }
            System.out.println();
        }
    }
}