Nth Fibonacci number

nth-fibonacci-num.java

public int nfibonacci(int n) {
  if (n == 1 || n == 2) return 1;
  if (n < 1) throw new RuntimeException("Invalid parameter. n must be greater than 0");
  int i = 1;
  int j = 1;
  int result = 0;
  for(int k = 3; k <= n; k++) {
    result = i + j;
    j = i;
    i = result;
  }
  return result;
}