/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static Set<List<Integer>> subsets(Set<List<Integer>> result, ArrayList<Integer> curr, int[] nums, int idx) {
    result.add((List<Integer>)curr.clone());
    if(idx < nums.length){
         subsets(result, curr, nums, idx + 1);
         final ArrayList<Integer> next = (ArrayList<Integer>) curr.clone();
         next.add(nums[idx]);
         subsets(result, next, nums, idx + 1);
    }
    return result;
}
public static void main(String[] args){
    int[] x = {1,2};
    System.out.println(subsets(new HashSet<>(), new ArrayList<>(), x, 0));
}
}

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