Java数组如何高效生成所有两位以上元素的组合和排列？

import java.util.*;

public class CombinationPermutation {

    public static void main(String[] args) {
        int[] nums = {11, 33, 22};
        generateCombinationsAndPermutations(nums);
    }

    public static void generateCombinationsAndPermutations(int[] nums) {
        for (int i = 2; i <= nums.length; i++) {
            List<List<Integer>> combinations = combine(nums, i);
            for (List<Integer> combination : combinations) {
                permute(combination, 0);
            }
        }
    }


    // 生成组合
    public static List<List<Integer>> combine(int[] nums, int k) {
        List<List<Integer>> result = new ArrayList<>();
        List<Integer> current = new ArrayList<>();
        backtrack(nums, result, current, 0, k);
        return result;
    }

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

    // 生成排列
    public static void permute(List<Integer> nums, int l) {
        if (l == nums.size()) {
            System.out.println(nums);
            return;
        }
        for (int i = l; i < nums.size(); i++) {
            Collections.swap(nums, l, i);
            permute(nums, l + 1);
            Collections.swap(nums, l, i); // 回溯
        }
    }
}