Java中如何高效穷举列表中两位以上元素的所有组合？

[11, 33]、[11, 22]、[11, 33, 22]、[11, 22, 33]、
[33, 22]、[33, 11]、[33, 11, 22]、[33, 22, 11]、
[22, 11]、[22, 33]、[22, 33, 11]、[22, 11, 33]

import java.util.*;

public class Test {

    public static void main(String[] args) {
        int[] nums = { 11, 33, 22 };
        for (int i = 2; i <= nums.length; i++) {
            combine(nums, new int[i], 0, 0);
        }
    }

    public static void combine(int[] nums, int[] temp, int start, int index) {
        if (index == temp.length) {
            permutation(temp, 0, temp.length - 1);
            return;
        }
        for (int i = start; i < nums.length; i++) {
            temp[index] = nums[i];
            combine(nums, temp, i + 1, index + 1);
        }
    }

    public static void permutation(int[] arr, int start, int end) {
        if (start == end) {
            System.out.println(Arrays.toString(arr));
        } else {
            for (int i = start; i <= end; i++) {
                swap(arr, start, i);
                permutation(arr, start + 1, end);
                swap(arr, start, i);
            }
        }
    }

    public static void swap(int[] arr, int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

}