CINUtil

public class CINUtil {

    public static String computeCin(String abi, String cab, String conto) {
        String result = null;

        String NUMERI = "0123456789";
        String LETTERE = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        int DIVISORE  = 26;
        int somma = 0;

        int[] aListaPari = new int[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25};
        int[] aListaDispari = new int[]{1, 0, 5, 7, 9, 13, 15, 17, 19, 21, 2, 4, 18, 20, 11, 3, 6, 8, 12, 14, 16, 10, 22, 25, 24, 23};

        String strAbiCabConto = abi + cab + conto;
        String strChar = "";
        int i = 0;

        for (int k = 1; k <= 22; k++) {
            strChar = strAbiCabConto.substring(k - 1, k);
            i = NUMERI.indexOf(strChar);
            if (i < 0) {
                i = LETTERE.indexOf(strChar);
            }

            i++;

            somma = somma + (k % 2 == 0 ? aListaPari[i - 1] : aListaDispari[i - 1]);
        }

        int y = 1 + (somma % DIVISORE);
        result = LETTERE.substring(y - 1, y);

        return result;
    }

}