#vulnerable code 
                                public SmsAlphabet getAlphabet()
    {
        switch (getGroup())
        {
        case GENERAL_DATA_CODING:
            // General Data Coding Indication
            if (dcs_ == 0x00)
            {
                return SmsAlphabet.ASCII;
            }

            switch (dcs_ & 0x0C)
            {
            case 0x00: return SmsAlphabet.ASCII;
            case 0x04: return SmsAlphabet.LATIN1;
            case 0x08: return SmsAlphabet.UCS2;
            case 0x0C: return SmsAlphabet.RESERVED;
            default:   return null;
            }
            
        case MESSAGE_WAITING_STORE_GSM:
            return SmsAlphabet.ASCII;
        
        case MESSAGE_WAITING_STORE_UCS2:
            return SmsAlphabet.UCS2;

        case DATA_CODING_MESSAGE:
            switch (dcs_ & 0x04)
            {
            case 0x00: return SmsAlphabet.ASCII;
            case 0x04: return SmsAlphabet.LATIN1;
            default:   return null;
            }
        
        default:
            return null;
        }                
    } 
                            #location 3 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public SmsAlphabet getAlphabet()
    {
        switch (getGroup())
        {
        case GENERAL_DATA_CODING:
            // General Data Coding Indication
            if (dcs_ == 0x00)
            {
                return SmsAlphabet.ASCII;
            }

            switch (dcs_ & 0x0C)
            {
            case 0x00: return SmsAlphabet.ASCII;
            case 0x04: return SmsAlphabet.LATIN1;
            case 0x08: return SmsAlphabet.UCS2;
            case 0x0C: return SmsAlphabet.RESERVED;
            default:   return SmsAlphabet.UCS2;
            }
            
        case MESSAGE_WAITING_STORE_GSM:
            return SmsAlphabet.ASCII;
        
        case MESSAGE_WAITING_STORE_UCS2:
            return SmsAlphabet.UCS2;

        case DATA_CODING_MESSAGE:
            switch (dcs_ & 0x04)
            {
            case 0x00: return SmsAlphabet.ASCII;
            case 0x04: return SmsAlphabet.LATIN1;
            default:   return SmsAlphabet.UCS2;
            }
        
        default:
            return SmsAlphabet.UCS2;
        }                
    }