添加新对象和调整大小后，GUI表现得很奇怪

Question

我有一个JPanel，它有一个按钮，按下时会创建一个新的圆圈。但是，这并没有发生。一个新的圆圈不会出现，当我调整窗口大小时，现有圆圈会断开，按钮的克隆会出现在面板的另一侧，所有东西都会冻结。

class Panel extends JPanel  {

    private JButton button;
    private Ellipse2D.Double[] circles;
    Integer count;

    public Panel()  {
            setup();
    }

    private void setup()  {
            count=new Integer(0);
            circles=new Ellipse2D.Double[10];
            button=new JButton(count.toString());
            button.addActionListener(new ActionListener() {
               @Override
               public void actionPerformed(ActionEvent e) {
                           circles[count]=new 
                              Ellipse2D.Double(10, 10, 100, 100);
                           count++;
                           button.setText(count.toString());
                    }
                });

               add(button);
        }


    public void paintComponent(Graphics g)  {
            super.paintComponent(g);
            paintStuff(g);
        }

    private void paintStuff(Graphics g)  {
            Graphics2D g2=(Graphics2D) g;
            g2.setPaint(Color.RED);
            Ellipse2D.Double circle2=new Ellipse2D.Double(getWidth()/2-
                    getHeight()/4,
                    getHeight()/4, getHeight()/2, getHeight()/2);
            g2.draw(circle2);

            if (count!=0)  {
                for (Ellipse2D.Double circle: circles)  {
                        g2.draw(circle);
                }
            }
    }
}

public class Frame extends JFrame  {
     private Panel panel;
     public Frame()  {
        panel=new Panel();
        add(panel);
     }

     public static void main(String[] args)  {
          Frame frame=new Frame();
     }
}

有什么问题，我应该怎么做才能解决它？