code exceeds time limit for one testcase

[nikhilniky]

import java.util.*;
public class Solution {

    public void helperset(ArrayList<Integer> arrset,int i,ArrayList<Integer> subSet,
                                               ArrayList<ArrayList<Integer>> ans){ 
    if(i==arrset.size()){
        if(!ans.contains(subSet))
        ans.add(subSet);
        return ;
    }
    subSet.add(arrset.get(i));
    helperset(arrset,i+1,new ArrayList<>(subSet),ans);
    subSet.remove(arrset.get(i));
     helperset(arrset,i+1,new ArrayList<>(subSet),ans);
    
}
public static ArrayList<ArrayList<Integer>> uniqueSubsets(int n, int arr[]) {
    // Write your code here..
     ArrayList<ArrayList<Integer>> ans = new ArrayList<ArrayList<Integer>> (); 
     ArrayList<Integer> subSet = new ArrayList<Integer>();
    ArrayList<Integer> arrset = new ArrayList<Integer>();
    Arrays.sort(arr);
    for(int i=0;i<n;i++){
       arrset.add(arr[i]);
    }
    Solution x =new Solution();
    x.helperset(arrset,0,subSet,ans);
    Collections.sort(ans, new Comparator<List<Integer>>() { 
        public int compare(List<Integer> o1, List<Integer> o2) { 
            int min = Math.min(o1.size(),o2.size());
            for(int i=0;i<min;i++)
            {
                 if(o1.get(i)!=o2.get(i))
                 {
                     return o1.get(i).compareTo(o2.get(i));
                 }
            }
            return (o1.size()<=o2.size())? -1:1;                
        }
    });
    return ans;
}

}