I have searched a lot and didn't find any thing useful that explains how to send PCL commands to a printer. I managed to do it and thought to share the code maybe some else will use it.

In My case I needed to send a PCL command to the citizen printer CT-S300 to print a barcode.

In the citizen Manual, it showed the examples in Basic language. Something like this:
//Note &H means Hexadecimal, and CHR$ function returns the charachter
//Following prints the barcode for number "123"
LPRINT CHR$(&H1D);"H";CHR$(2);
LPRINT CHR$(&H1D);"k";
LPRINT "123";CHR$(0);

And this is the Java code I used for printing:
//Preparing command String
String barcode = "123";
String printBarCodeCommand = (char) 29 + "k" + (char) 4 + barcode + (char) 0;
//Below code is to send the string to the printer
HashPrintRequestAttributeSet aset;
PrintService printServices;
InputStream input;
DocFlavor flavor;
DocPrintJob job;
Doc doc;
input = new ByteArrayInputStream(printBarCodeCommand.getBytes( ));
aset = null;
printServices = GetPrintService("Citizen CT"); //I will not include code for this function, you can search for it its easy to look up a PrintService
job = services2.createPrintJob();
doc = new SimpleDoc(input, flavor, null);
job.print(doc, aset);

This should do the job. Please also note that some commands need to be at the beggining of a line, or they will not be executed.

Hope this helps somebody out there.
Ahmad Khudairy