I can't throw my exception

Question

I created my exception
public class wyjatek extends Exception {
    public wyjatekNieobslugiwany() {
}i can throw him in my code:
   try{
                                try{
                         x= request.getParameter("x");
                         y= request.getParameter("y");
                    } catch (NullPointerException npe){
                         throw new wyjatek();
                                if (x.equals(y)){
                                    out.println('equal')
    } catch (wyjatek w){
    }but i have NullPointerException. Code after throw new wyjatek() is executing.
Why?
I change line "throw new wyjatek()" to "throw new Exception()" and everything was fine. Why I can properly throw Exception() but I can't throw wyjatek() witch extends Exception()?

Answer 1

but i have NullPointerException. Code after throw new wyjatek() is >executing.Wrong, that's the code throwing NPE.
try{
     //A NPE Exception will never be thrown here
       x= request.getParameter("x");
      y= request.getParameter("y");
} catch (NullPointerException npe){
      throw new wyjatek();
if (x.equals(y)){ //this is where NPE will be thrown if x or y is null
     out.println('equal')
}For your exception to be thrown (cant figure out why you should throw CustomExceptions on NP, though)
      x= request.getParameter("x");
      y= request.getParameter("y");
      try{
                 if (x.equals(y)){
                     out.println('equal')
          }catch(NullPointerException npe){
               throw new wyjatek(npe.getMessage());
      }cheers,
ram.