Send and recieve 2 byte integer values.

Question

hi,
basically i'm trying to allow my applet and servlet communicate using 2 byte signed integer values. but i haven't figured out how to store an integer value into a byte array of size 2, or unpack it once it gets there.
here's some code/psuedocode that i've done so far.
SERVLET:
ByteArrayOutputStream bst = new ByteArrayOutputStream(streamsize);
ServletOutputStream bout;
byte[] strm = new byte[streamsize];
byte[] dbyte = new byte[2];
int[] testarr = new int[10];
/* fill my testarr with values... */
bout = response.getOutputStream();
int l = 0;
for (int i = 0;i<arraysize;i++){
getDoubleByteFromInteger(dbyte,testarr)
strm[l++] = dbyte[0];
strm[l++] = dbyte[1];
bst.write(strm,0,streamsize);
bst.writeTo(bout);
APPLET:
/* connect to servlet and get binary stream */
bytecount = in.read(streamb);
byte[] db = new byte[2];
counter = 0;
while (cursor < bytecount){
db[0] = streamb[cursor++];
db[1] = streamb[cursor++];
array[counter++] = getIntFromByte(db);
the functions getIntFromByte and getDoubleByteFromInteger haven't been written, can anyone give me a little push? or tell me if this is something possible? thanks for any help
Matt

Answer 1

The primitive type short is a two-byte signed integer, so you really don't need to bother with byte arrays - just use DataOutputStream to write it (it has a method called writeShort) and DataInputStream to read it (with readShort()).
But anyway, getting an int from two bytes and getting two bytes from an int is easy with the bitwise operators:
int -> byte array
int i = yourInt;
byte[] b = new byte[2];
b[1] = (byte) (i >> 8);
b[0] = (byte) (i);
byte array -> int (unsigned)
int i = ((b[1] & 0xFF) <<8) + (b[0] & 0xFF);
byte array -> short -> int (signed)
short s = (short) ((b[1] & 0xFF) <<8) + (b[0] & 0xFF);
int i = s;