/* 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(int[] nums) {
      final Set<List<Integer>> result = new HashSet<>();
      for(int i = 0; i < 1 << nums.length; i++){
         final List<Integer> curr = new ArrayList<>();
         for(int j = 0; j < nums.length; j++){
            if(((i>>j)&1)==1) curr.add(nums[j]);
         }
         result.add(curr);
      }
      return result;
}
public static void main(String[] args){
    int[] x = {1,2,};
    System.out.println(subsets(x));
}
}

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