Animation ball on curve

BallOnCurveFrame.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class BallOnCurveFrame extends JFrame {

    private BallOnCurvePanel curvePanel = new BallOnCurvePanel();

    BallOnCurveFrame() {
        curvePanel.setBackground(Color.black);
        add(curvePanel);
    }

    public static void main(String[] args) {
        JFrame frame = new BallOnCurveFrame();
        frame.setTitle("Ball on Curve");
        frame.setSize(400, 250);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

class BallOnCurvePanel extends JPanel {

    private int n = -175;
    private int position = -1;
    private Timer timer = new Timer(25, new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (n == 175) {
                position = -1;
            } else if (n == -175) {
                position = 1;
            }

            if (position == -1) {
                n--;
            } else if (position == 1) {
                n++;
            }
            repaint();
        }
    });

    public BallOnCurvePanel() {
        timer.start();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        Polygon polygon = new Polygon();
        for (int x = -175; x <= 175; x++) {
            polygon.addPoint(x + 200, 100 - (int) (50 * 
                    Math.sin((x / 100.0) * 2 * Math.PI)));
        }

        g.drawPolyline(polygon.xpoints, polygon.ypoints, polygon.npoints);
        g.setColor(Color.ORANGE);
        if (n >= -175 && n <= 175) {
            g.fillOval(n + 200 - 5, 100 - (int) (50
                    * Math.sin((n / 100.0) * 2 * Math.PI)) - 5, 10, 10);
        }
    }
}