public CheckOut()
    {
        gc = GroceryController.getInstance();
        observers = new ArrayList<PhoneNumberObserver>() ;
        field0 = new NoFieldEntered( this ) ;
        field1 = new OneFieldEntered( this ) ;
        field2 = new TwoFieldsEntered( this ) ;
        field3 = new ThreeFieldsEntered( this ) ;
        this.state = field0 ;
        this.pin = Pin.getInstance() ;
    }