code: public static int gcd(int[] numbers) {
  
      if (numbers.length == 1)
        return numbers[0];
  
      int g = gcd(numbers[0], numbers[1]);
  
      for (int i = 2; i < numbers.length; i++)
        g = gcd(g, numbers[i]);
  
      return g;
    }
docs: Determines the greatest common divisor (GCD) of a list
  of integers.
  
  @param numbers the list of integers to process
  
  @return the greatest common divisor of all numbers