使用目标c

Question

请帮助我，我是目标c或c编程的新手，我在基于数据转换的计算中很挣扎

字节b1 =

 hexStringToByteArray(workingData.charAt(begin));

      String bbb= String.valueOf(b1);
        int ch1 = ((b1 & 0xC0) >> 6);
        String ccc=  String.valueOf(ch1);
        int ch2 = ((b1 & 0x30) >> 4);
        String dddd=  String.valueOf(ch2);
        dtc += dtcLetters[ch1];
        String eeee=  String.valueOf(dtcLetters[ch1]);
        dtc += hexArray[ch2];
        String eeeedd=  String.valueOf( hexArray[ch2]);
        dtc += workingData.substring(begin + 1, 
begin + 4);

        String dfdf=  String.valueOf(workingData.substring(begin + 1, begin + 4));
        if (dtc.equals("P0000")) {
            return;
        }
        codes.append(dtc);
        codes.append('\n');
    }
}

private byte hexStringToByteArray(char s) {
    return (byte) ((Character.digit(s, 16) << 
4));
}