给定一个数组，返回这个数组的所有子数组

import java.util.*;public class Solution {    public ArrayList<ArrayList<Integer>> subsets(int[] S) {          ArrayList<ArrayList<Integer>> result=new ArrayList<ArrayList<Integer>>();        Arrays.sort(S);        ArrayList<Integer> subList=new ArrayList<Integer>();        for (int i=0;i<=S.length;i++){            func(S,i,0,subList,result);        }        return result;             }    public void func(int[] S,int num,int index,ArrayList<Integer> subList,ArrayList<ArrayList<Integer>> result){        if (num<0){            return;        }else if (num==0){            result.add(new ArrayList<Integer>(subList));        }else {            for (int j=index;j<S.length;j++){                subList.add(S[j]);                func(S,num-1,j+1,subList,result);                subList.remove(subList.size()-1);            }         }        }}