How is BigO complexity equation calculated in general?

Question

In worst case(failed to find sum ending up return false), what would be the complexity equation of the code and what's BigO of it? I put // and number of times either 1, n, n^2 that I think right. Could you check if I am calculating it right?

public static boolean hasSum(int arr[], int sum){

        int n = arr.length;           //1

        for(int i =0; i<n; i++) {           // 1, n, n
            for(int j =0; j<n; j++) {      //1, n^2, n^2
                if(arr[i] +arr[j]==sum) {       //n^2
                    return true;
                }
            }
        }


    return false;      //1   (because it fails to find the sum)
}

So what I have is 3n^2 + 2n +4 , which is O(n^2)

I think I may be right on BigO, but not sure about the equation that I made.

Is it correct?

Thank you!