Time complexity of this code to list all subsets of a set?

I have found numerous solutions across the web having O(2^n) complexity. Can someone help me figure out the time complexity of the code given below. Also it involves lot of bit manipulation and I am really weak in that area so I didn't quite get the hang of the code. Would be great if someone could explain the code.

private static void findSubsets(int array[])
{
  int numOfSubsets = 1 << array.length; 

  for(int i = 0; i < numOfSubsets; i++)
  {
    int pos = array.length - 1;
    int bitmask = i;

    System.out.print("{");
    while(bitmask > 0)
    {
      if((bitmask & 1) == 1)
         System.out.print(array[pos]+",");
     {
        bitmask >>= 1;
        pos--;
     }
     System.out.print("}");
  }
}

Is this the most optimal solution?