I created the following code injava, but I am not sure how to explain what this method does. Can someone please help me explain this method

/Time complexity for the following is 0C1) public static long fib Clong n) if(n) return 0 double num = Math. pow(CC1 + Math.sqrt(5)) / 2), n + 1) -Math. powCCC1 - Math.sqrt(5)) / 2), r return (long) (num/ Math.sqrt(5));