Comm api 2.0 - CommPortIdentifier.getPortIdentifiers() returns empty enum

hi all
i am facing problem to read input from com port
i am using javax.com package on a windows machine

the program is:

import java.io.*;
import javax.comm.*;
import java.util.*;

public class PortReader implements SerialPortEventListener {
static Enumeration ports;

static CommPortIdentifier pID;

InputStream inStream;

SerialPort serPort;

public PortReader() throws Exception{
serPort = (SerialPort) pID.open("PortReader", 2000);
inStream = serPort.getInputStream();

serPort.addEventListener(this);

serPort.notifyOnDataAvailable(true);

serPort.setSerialPortParams(9600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
}

public void serialEvent(SerialPortEvent event) {
switch (event.getEventType()) {
case SerialPortEvent.BI:
System.out.println("SerialPortEvent.BI occurred");
case SerialPortEvent.OE:
System.out.println("SerialPortEvent.OE occurred");
case SerialPortEvent.FE:
System.out.println("SerialPortEvent.FE occurred");
case SerialPortEvent.PE:
System.out.println("SerialPortEvent.PE occurred");
case SerialPortEvent.CD:
System.out.println("SerialPortEvent.CD occurred");
case SerialPortEvent.CTS:
System.out.println("SerialPortEvent.CTS occurred");
case SerialPortEvent.DSR:
System.out.println("SerialPortEvent.DSR occurred");
case SerialPortEvent.RI:
System.out.println("SerialPortEvent.RI occurred");
case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
System.out.println("SerialPortEvent.OUTPUT_BUFFER_EMPTY occurred");
break;
case SerialPortEvent.DATA_AVAILABLE:
System.out.println("SerialPortEvent.DATA_AVAILABLE occurred");
byte[] readBuffer = new byte[20];

try {
while (inStream.available() > 0) {
int numBytes = inStream.read(readBuffer);
}
System.out.print(new String(readBuffer));
} catch (IOException ioe) {
System.out.println("Exception " + ioe);
}
break;
}
}

public static void main(String[] args) throws Exception{
ports = CommPortIdentifier.getPortIdentifiers();

while (ports.hasMoreElements()) {
pID = (CommPortIdentifier) ports.nextElement();
System.out.println("Port " + pID.getName());

if (pID.getPortType() == CommPortIdentifier.PORT_SERIAL) {
if (pID.getName().equals("COM1")) {
PortReader pReader = new PortReader();
System.out.println("COM1 found");
}
}
}
}

}

when running this alone i get the response

Port com1
COM1 found
port com6
port com7
port com8
portLPT1
port LPT2

but when i use a gps simulator to output on the com1 port
while running the program simulator pops a message "com1 in use"

And when i run the gps simulator first the the program the the program gives
the exception:
Exception in thread "main" javax.comm.portInUseEXception:Port currently
owned by gps_simulator_com1

pls suggest a way how to read output from the simulator through com1 by the program