如何用计时器重新粉刷？

Question

我想用计时器提供射弹动作。首先，我创建计时器，然后用计时器更改x和y的位置。当我检查所有X和Y点都已更新但我无法重新绘制新的X和Y.如何重新绘制我的面板并提供抛射物运动？提前致谢。这是我的代码。

import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Deneme extends JPanel {

    double positionY = 100;
    double positionX = 100;
    double velocityY = 20;
    double velocityX = 20;
    double acceleration = -10;
    Timer timer;

    public Deneme() {
        timer = new Timer(100, new myTimerListener());
    }

    private class myTimerListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            update(0.09);
            repaint();
        }

    }

    void update(double dt) {
        positionX += velocityX * dt;
        positionY += velocityY * dt + acceleration * 0.5 * dt * dt;
        velocityY += acceleration * dt;
        System.out.println(positionX + " " + positionY);
    }

    @Override
    public void paint(Graphics g) {
        super.paint(g);
        g.drawOval((int) positionX, (int) positionY, 15, 15);
    }

    public double positionY() {
        return positionY;
    }

    public double velocityY() {
        return velocityY;
    }

    public double positionX() {
        return positionX;
    }

    public double velocityX() {
        return velocityX;
    }

    public static void main(String[] args) {
        new Deneme().timer.start();
        JFrame frame = new JFrame("Basketball");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(1500, 1000);
        frame.add(new Deneme());
        frame.setLocationRelativeTo(null);
        frame.setResizable(false);
        frame.setVisible(true);
    }
}