Java數組如何高效生成所有兩位以上元素的組合和排列？

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);             }         }     }       // 生成組合     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         }     } }