android MD5

public static String MD5(String str)
        {
            MessageDigest md5 = null;
            try
            {
                md5 = MessageDigest.getInstance("MD5");
            }catch(Exception e)
            {
                e.printStackTrace();
                return "";
            }  

            char[] charArray = str.toCharArray();
            byte[] byteArray = new byte[charArray.length];  

            for(int i = 0; i < charArray.length; i++)
            {
                byteArray[i] = (byte)charArray[i];
            }
            byte[] md5Bytes = md5.digest(byteArray);  

            StringBuffer hexValue = new StringBuffer();
            for( int i = 0; i < md5Bytes.length; i++)
            {
                int val = ((int)md5Bytes[i])&0xff;
                if(val < 16)
                {
                    hexValue.append("0");
                }
                hexValue.append(Integer.toHexString(val));
            }
            return hexValue.toString();
        }