Java swing application not working -

here image of application:

when new button pressed question displayed , timer starts.

but after 'new' button pressed neither timer runs nor text displayed , default close operation not work. when comment out checktimer() working fine.

here code:

if(buttonevent.getactioncommand().equals("new")){                 string store = buttonevent.getactioncommand();                 startgame();                 checktimer();              panelone.remove(buttonnew);             panelone.revalidate();             panelone.repaint();         }  public void startgame(){     // todo auto-generated method stub     string line = null;     try{         bufferedreader reader = new bufferedreader(new filereader("c:\\users\\mypc\\documents\\myfile.txt"));         while((line = reader.readline()) != null){             system.out.println(line);             queue.add(line);         }         reader.close();     }     catch(ioexception exception){         exception.printstacktrace();     }        // flag = true;         string display = queue.remove();         textarea.settext(display);         //checktimer(); }        public void checktimer() {     // todo auto-generated method stub      int sec = 59;     int min = integer.parseint(timerfield1.gettext());      while(min >= 0){         min--;         if(min >= 0){             for(int = 0; < 60; i++){                 try{                     thread.sleep(1000);                 }                 catch(interruptedexception ie){                     thread.currentthread().interrupt();                 }                  timerfield1.settext(integer.tostring(min));                 timerfield2.settext(integer.tostring(sec));                 if(sec > 0){                     sec--;                 }                 else{                     break;                 }             }         }         //textarea1.settext(integer.tostring(num));         sec = 59;     }  } 

please guide me why not working.

thread.sleep(1000); 

don't use thead.sleep when code executing on event dispatch thread (edt). cause gui freeze , prevent gui responding events.

when new button pressed question displayed , timer starts.

then should using swing timer. set timer fire every second can update time. after if fires 300 times stop timer , game over.

read section swing tutorial on how use swing timers more information , working examples.