If else loop not adding valuing to variable using +=? [closed]

I have a 1D matrix with data and another with scores. I'm trying to loop across all of the elements in the data and find the element in the same position in the score matrix, and keep adding these values together during each loop. For some reason, my script keeps starting from sum = zero instead of retaining and adding to the sum from the previous loop. For the below example, I expect sum = 1 in the first loop, 3 after the second loop (since 1+2=3) and 6 after the third loop (3+3=6). Instead, sum just yields the last value retrieved from scores. What am I doing wrong here?

public static int calc_score( ) 
    {
        String [] dat = {"A", "B","C"};
        int [][] scores = new int [1][3];
        scores[0][0] = 1;
        scores[0][1] = 2;
        scores[0][2] = 3;
        
        int sum = 0;
        for (int i = 0; i < dat[0].length(); i++)
        {
            if (dat[i].equals("A")) {
                sum = sum + scores[i][0];
// scores[i][0] returns the expected value of 1 in the first loop
            }
                
            else if (dat[i].equals("B")) {
                sum = sum + scores[i][1];
            }
                
            else if (dat[i].equals("C")) {
                sum = sum + scores[i][2];
            }
                
            
        }
        System.out.println(sum);
        return sum;
        
        
    }

I tried modifying sum = sum + scores[i][1]; to sum+=scores[i][1] but that doesn't fix this. I have to be missing something simple.