class Car
{
  void startengine(){};
}
public class NullExceptionDemo{
  Car mycar;
  void start() throws InstantNotInitException{
   if (mycar==null) throw new InstantNotInitException("mycar is null");
   mycar.startengine();}
public static void main(String args[]){
   NullExceptionDemo demo=new NullExceptionDemo();
 try{
       demo.start();
       System.out.println("start car"); 
       return;
  }catch(InstantNotInitException e){
       System.out.println("Got exception:"+e.getMessage()); }}
}
class InstantNotInitException extends Exception{
   public InstantNotInitException(){}
  public InstantNotInitException(String message) {super(message);}
}