java求集合的子集

给定一个含不同整数的集合，返回其所有的子集

import java.util.*;
public class Solution {

/*
 * @param nums: A set of numbers
 * @return: A list of lists
 */
public List> subsets(int[] nums) {
    int len = 1 << nums.length;
    List> lists = new LinkedList>();
    for (int i = 0; i < len; i++) {
        List list = new LinkedList();
        int index = i;
        for (int j = 0; j < nums.length; j++) {
            if ((index & 1) == 1) {
                list.add(nums[j]);
            }
            index >>= 1;
        }
        Collections.sort(list);
        lists.add(list);
    }
    return lists;
}

}