I'm unable to access Serial Port

Question

I have written following code but I m getting NullPointerException on line 13 of this code, please solve my problem and identify error.
In this code I have used chaeron api which is available at www.chaeron.com
import com.chaeron.GPS.NMEA.*;
import com.chaeron.GPS.*;
import com.chaeron.platform.SerialPort;
public class MyGPS1 //extends NMEAGPSImpl
     public static void main(String st[]) throws Exception
          SerialPort sp = null;
          NMEAGPSImpl gps = new NMEAGPSImpl();
          sp = gps.getSerialPort();//returning null
          if(sp.isOpen())
               gps.setSerialPort(2);
               gps.connect();
          System.out.println(sp.isOpen());//error on this line

Answer 1

generally serial port problems stem from incorrect installation of the javax.comm package: does the serial demo work? It's hard to say what the problem is without knowing anything about the gps object.