java - Conversion from long to four-character hex string -

updated question 01/28/2016:

since question wasn't terribly clear before (i'm learning still), here re-write of post:

here scenario find myself in:

i have code written reads data log file containing gps coordinates formatted in following way in hex:

"x1 x2 x3 x4 y1 y2 y3 y4"

where x's latitude component , y's longitude component. code converts these messages values latitude/longitude in degrees performing following sequence:

string strhexlat = x1 + x2 + x3 + x4; //(x1x2x3x4 viewed 1 hex value) string strhexlon = y1 + y2 + y3 + y4; //(y1y2y3y4 viewed 1 hex value)  int intlat = integer.decode(strhexlat); int intlon = integer.decode(strhexlon);  if ((intlat & 0x40000000) != 0) {     intlat |= 0x80000000; } if ((intlon  & 0x40000000) != 0) {     intlon  |= 0x80000000; }  double lat = (double) intlat / 3600000; // convert mas deg double lon = (double) intlon / 3600000; // convert mas deg 

despite not being particularly elegant, above code want to. real trouble begins reversing process. trying write code create log files in same format existing files, starting coordinates , generating 8 character hex array representing coordinates.

the following snippets have perform conversion, along sample inputs, resulting outputs, , desired outputs:

(1) convert coordinates in degrees milliarcseconds:

/* test coordinates */ mlat = 42.281422; mlon = -83.748552;  /* convert values degrees milliarcseconds*/ long convlat = (long)(mlat * 3600000.0); long convlon = (long)(mlon * 3600000.0); 

inputs:

mlat = 42.281422   mlon = -83.748552   

outputs:

convlat = 152213119   convlon = -301494787   

desired outputs:
above output desired.

(2) account negative values:

/* account negative values */ if(convlat < 0) convlat = convlat & 0x00000000ffffffffl; if(convlon < 0) convlon = convlon & 0x00000000ffffffffl; 

inputs:

convlat = 152213119   convlon = -301494787   

outputs:

convlat = 152213119   convlon = 3993472509   

desired outputs:
above output desired.

(3) split value 4 values (just trying latitude component now):

/* split 4 values */ byte[] datalat = new byte[4]; datalat[0] = (byte) ( ( convlat >>> 24 ) & 0xff ); datalat[1] = (byte) ( ( convlat >>> 16 ) & 0xff ); datalat[2] = (byte) ( ( convlat >>> 8 ) & 0xff ); datalat[3] = (byte) ( ( convlat >>> 0 ) & 0xff ); 

inputs:

convlat = 152213119   

outputs:

datalat[0] = 9   datalat[1] = 18   datalat[2] = -106   datalat[3] = 127   

desired outputs:
***** not entirely negative values.

(4) convert values single hex string:

/* convert 1 hex string per component */ string hexlat = long.tohexstring(convlat); string hexlon = long.tohexstring(convlon); 

inputs:

convlat = 152213119   convlon = 3993472509   

outputs:

hexlat = "912967f"   hexlon = "ee078dfd"   

desired outputs:
these values valid, , can converted desired value in degrees.

if:
convlat = 152213119 converted "912967f"
want:
convlat = 152213119 become "09 12 96 7f"
where:
of 4 hex values can either 1 or 2 digits , padded on left 0's, in case first digit of four.

(5) convert values 4 hex strings:

/* convert 4 hex strings per component */ string[] hexstringlat = new string[4]; hexstringlat[0] = integer.tohexstring(datalat[0]); hexstringlat[1] = integer.tohexstring(datalat[1]); hexstringlat[2] = integer.tohexstring(datalat[2]); hexstringlat[3] = integer.tohexstring(datalat[3]); 

inputs:

datalat[0] = 9   datalat[1] = 18   datalat[2] = -106   datalat[3] = 127   

outputs:

hexstringlat[0] = "9"   hexstringlat[1] = "12"   hexstringlat[2] = "ffffff96"   hexstringlat[3] = "7f"   

desired outputs:
when converting single hex string value "912967f"

which want in form of 4 strings mentioned above, "09 12 96 7f".

when converting directly 4 hex values, however, "9 12 ffffff96 7f".
in case padding operation simple, not want 3 value negative.

questions:
why third value negative when converting directly 4 hex characters , not when converting 1 hex string?

is there 'easy' way convert single string format desire?
write sloppy code run single code through try different ways of splitting values , testing string converts back, seems wrong way go it.

note: have found following helpful, not complete scenario in:
how perform unsigned signed conversion in java?

thanks in advance help, , apologize if have again left out necessary details, please ask , update again possible if need more info.

i haven't tested this, can't use string.format?

string.format ("%02x %02x %02x %02x", (byte) ( ( convlat >>> 24 ) & 0xff ), etc.

that is, break out each byte, have done shifting , masking, , passing them parameters string.format.

the 02 ensures 2 digits, adding leading 0 if necessary. upper case x means use hex , use upper case a-f.