creating UDH of message in java

[soumya dash]

I want to create UDH of a message string.

I am doing these following operations:

 
String strmsg =  "30 AM-11:00 AM?vV?W&FRGVR??7J(No Location)???11/8 4:30 PM-5:30 PM????F????
                                                  B7FGW2&Wf?Wr???F?&??V7G:Conference Call";
int udhlen;

if (isHexString(strmsg) == false)
{
    System.out.println("Strmsg :" + strmsg);
    byte[] msgarr = strmsg.getBytes();
    udhlen = (int)msgarr[0];
    System.out.println(udhlen);

    if (udhlen > 24)
    {
        display("udh length is greather");
        commandStatus = 0x00000045;
        response.setCommandStatus(commandStatus);
        break;
    }
    udh = "";
    for (int i = 0; i < udhlen + 1; i++)
    {
        udh = udh + (((int)msgarr[i] < 0x10) ? "0" + Integer.toHexString((int)msgarr[i]) : 
                                                                             Integer.toHexString((int)msgarr[i]));
        System.out.println("123" + udh);

        if (i == 3 && (int)msgarr[i] < 0)
        {
            udh = udh + "2b";
            i = i + 2;
            udhlen = udhlen + 2;
        }
        else
        {
            udh = udh + (((int)msgarr[i] < 0x10) ? "0" + Integer.toHexString((int)msgarr[i]) : 
                                                                                  Integer.toHexString((int)msgarr[i]));
        }
        System.out.println(udh);
        int l = msgarr.length - udhlen - 1;
        byte msgarr1[] = new byte[l];
        for (int j = udhlen + 1, k = 0; j < msgarr.length; j++, k++)
            msgarr1[k] = msgarr[j];
        strmsg = null;
        strmsg = new String(msgarr1);
        strmsg = Hex2DecimalNew.decimal2hexString(new String(msgarr1));
        msgarr = null;
        msgarr1 = null;
    }

and the result should be : udhlen=5 so that I'll get the UDH in my desired format.

But, for certain messages, the udhlen is coming negative. I did something to handle the negative value of (int)msgarr[i] yet my purpose is not fulfilled.

I am new in SMS technology. Please help me to improve my code and solve the issue. Thanks in advance.