private static String getPostionInBase64Table(char c) {
        if((c >= 65 && c <= 90))// Gro�buchstabe
            return c - 65 + "";
        else if((c >= 97 && c <= 122))// Kleinbuchstabe
            return c - 71 + "";
        else if((c >= 48 && c <= 57))// Ziffern
            return c + 4 + "";
        else if(c == 43)// Sonderzeichen +
            return c + 19 + "";
        else return c + 16 + "";
    }