different output trying to execute same java code

i am using net beans 7 ide and java 6 to develop my java projects. i used the following coding to read value from serial port :

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

public class SimpleRead implements Runnable, SerialPortEventListener {

static CommPortIdentifier portId;
 static Enumeration portList;

InputStream inputStream;
SerialPort serialPort;
Thread readThread;

public static void main(String[] args) {


portList = CommPortIdentifier.getPortIdentifiers();
JOptionPane.showMessageDialog(null, "portList :"+portList.hasMoreElements()); 
while (portList.hasMoreElements()) {
  portId = (CommPortIdentifier) portList.nextElement();
  if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
   if (portId.getName().equals("COM3")) {
         SimpleRead reader = new SimpleRead();
  }
}

} }

public SimpleRead() {
 ....

...... }

public void run() {
  try {
    Thread.sleep(20000);
  } catch (InterruptedException e) {System.out.println(e);}
}

public void serialEvent(SerialPortEvent event) {
  switch(event.getEventType()) {
    .....

...... ..... ...... } } }

When i execute from netbeans, JOptionPane showing "portList : true" but when i double click on the jar file and tried to run, JOptionPane showing "portList : false"

Why there is different output trying to execute same java code