StringBuilder go(StringBuilder s, int n) {
        StringBuilder sb = new StringBuilder();
        int q = 0;
        for (int i = s.length() - 1; i >= 0; i--) {
            int m = ((int) (s.charAt(i) - '0')) * n + q;
            sb.append(m % 10);
            q = m / 10;
        }
        if (q != 0)
            sb.append(q);
        return sb.reverse();
    }
Why Did you create this class? what does it do?
src/problems/medium/MultiplyStrings.java