NullPointerException

[oll3i]

 
    private List<Klient> klienci;
 
 
 
 m_add_client.addActionListener( new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
 
try{
 
 
klienci.add(new Klient((String)m_name.getText(),Double.valueOf(m_money.getText().trim()).doubleValue()));                       
 
}catch(NumberFormatException exception){
System.err.println("Nie podana suma pieniedzy");
}  
catch(NullPointerException exception){
System.err.println("?");
}
}
});
 
 m_add.addActionListener( new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
 
                        try{
                        Cennik c= Cennik.getInstance();
                        Klient klient = new Klient((String)m_name.getText(),Double.valueOf(m_money.getText().trim()).doubleValue()); 
                        if(klienci.contains(klient)){
                            int index=klienci.indexOf(klient);
                            klient=klienci.get(index);
                        }
 
                        String wybrany_kwiat= (String)kwiatyList.getSelectedItem();
                        System.out.print(wybrany_kwiat);
                        int a=Integer.parseInt(m_amount.getText());
                        table.addRow(wybrany_kwiat,a,c.getCenna(wybrany_kwiat));
 
                        if("Roza Czerwona".equals(wybrany_kwiat)){
 
                        klient.dodajDoWozka(new RozaCzerwona(),a);
 
                        }else if("Roza Biala".equals(wybrany_kwiat)){
 
                      klient.dodajDoWozka(new RozaBiala(),a);
 
                       }else if("Roza Zolta".equals(wybrany_kwiat)){
                        klient.dodajDoWozka(new RozaZolta(),a);
 
                       }else if("Roza Czarna".equals(wybrany_kwiat)){
 
                        klient.dodajDoWozka(new RozaCzarna(),a);
 
                      }else if("Tulipan Zolty".equals(wybrany_kwiat)){
 
                        klient.dodajDoWozka(new TulipanZolty(),a);
 
                      }else if("Tulipan Czerwony".equals(wybrany_kwiat)){
 
                        klient.dodajDoWozka(new TulipanCzerwony(),a);
 
                      }else if("Tulipan Bialy".equals(wybrany_kwiat)){
 
                        klient.dodajDoWozka(new TulipanBialy(),a);
 
                      }else if("Lilia Biala".equals(wybrany_kwiat)){
 
                        klient.dodajDoWozka(new LiliaBiala(),a);
 
                      }else if("Lilia Zolta".equals(wybrany_kwiat)){
 
                        klient.dodajDoWozka(new LiliaZolta(),a);
 
                      }else if("Lilia Rozowa".equals(wybrany_kwiat)){
 
                        klient.dodajDoWozka(new LiliaRozowa(),a);
 
                      }
 
                        }catch(NullPointerException exception){
 
                             System.err.println("Funkcja c.getCenna(wybrany_kwiat)");
                        }
                        label_koszyk.setText("Do zaplaty:" + kwiaciarnia.doZaplaty());     
 
 
                    }
                  });   
 
 
 
 
 
 

somewhere here i get nullpointerexception but where ?

[RedSon]

Does it give you a line number of the exectption?

[oll3i]

no it doesnt

[oll3i]

the nullpointerexception is in a line with klient.dodajDoWozka(new RozaCzerwona(),a);

[oll3i]

public class Roza extends Kwiat{
 
    public Roza(){
    }
    protected String get_nazwa(){return nazwa;}
    protected  double get_cena() {return cena;}
    protected  void set_nazwa(String n){nazwa=n;}
    protected  void set_cena(double c){cena=c;}
}
public class RozaCzerwona extends Roza{
String nazwa="Roza Czerwona";
 
public RozaCzerwona(){}
}
 

why RozaCzerwona r= new RozaCzerwona(); returns null

[JosAH]

This is the show stopper:

catch(NullPointerException exception){
System.err.println("?");
}

The exception could've given you all the information you need but all you do
is print a single question mark instead. At least do this in the body of your
exception handler and see the entire stack trace:

exception.printStackTrace();

Never ever hide information you might need.

kind regards,

Jos

[oll3i]

i know that nullpointerexception is caused by klient.dodajDoWozka(new RozaCzerwona(),a); cos new RozaCzerwona() returns null

[JosAH]

The new operator can never return null. The cause of your NullPointerException
is somewhere else.

kind regards,

Jos

[oll3i]

i checked it i commented out everything
and this line klient.dodajDoWozka(new RozaCzerwona(),a);caused nullpointerexception

then i did
RozaCzerwona r= new RozaCzerwona();
System.out.println(r.get_nazwa());<<< this prints null

[JosAH]

i checked it i commented out everything
and this line klient.dodajDoWozka(new RozaCzerwona(),a);caused nullpointerexception

then i did
RozaCzerwona r= new RozaCzerwona();
System.out.println(r.get_nazwa());<<< this prints null

That only shows that your 'get_nazwa()' method returned null.

kind regards,

Jos

[oll3i]

yes but why

this are the classes

public class RozaCzerwona extends Roza{
String nazwa="Roza Czerwona";
 
public RozaCzerwona(){}
}
 
public class Roza extends Kwiat{
 
    public Roza(){
    }
    protected  String get_nazwa(){return nazwa;}
    protected  double get_cena() {return cena;}
    protected  void set_nazwa(String n){nazwa=n;}
    protected  void set_cena(double c){cena=c;}
}
 
public abstract class Kwiat {
    String nazwa;
    double cena;
    protected abstract String get_nazwa();
    protected abstract double get_cena();
    protected abstract void set_nazwa(String n);
    protected abstract void set_cena(double c);
}
 

[JosAH]

yes but why

this are the classes

public class RozaCzerwona extends Roza{
String nazwa="Roza Czerwona";
 
public RozaCzerwona(){}
}
 
public class Roza extends Kwiat{
 
    public Roza(){
    }
    protected  String get_nazwa(){return nazwa;}
    protected  double get_cena() {return cena;}
    protected  void set_nazwa(String n){nazwa=n;}
    protected  void set_cena(double c){cena=c;}
}
 
public abstract class Kwiat {
    String nazwa;
    double cena;
    protected abstract String get_nazwa();
    protected abstract double get_cena();
    protected abstract void set_nazwa(String n);
    protected abstract void set_cena(double c);
}
 

You have *two* Strings "nazwa": one in the abstract base class Kwiat and
another one in the derived class RozaCzerwona. You initialize the latter
but the String in the base class still equals null and that is the one returned
by your get_nazwa() method.

Change your constructor in that derived class to:

public RozaCzerwona(){
   set_nazwa("Roza Czerwona");
}

... and remove that String nazwa in the derived class.

kind regards,

Jos

[oll3i]

that fixed the problem thank u very much :)

[JosAH]

that fixed the problem thank u very much :)

You're welcome of course; please reread my reply #6 again: you effectively
had hidden the fact that your variable was still null; your exception could've
told you that in its stack trace, but you didn't allow it to tell you so, so Eclipse
assumes that you've handled the exception and doesn't panic either.

Always let those exceptions tell what they want to tell you during the
development phase of your program. Only when you know what do handle
and what not you can take those stacktraces out of your program.

kind regards,

Jos