用中点算法在java中画圆

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

public class CircleDrawing extends JPanel {
    private void drawCircle(Graphics g, int x, int y, int radius) {
        int d = 1 - radius;
        int xPos = 0;
        int yPos = radius;

        while (xPos <= yPos) {
            drawSymmetricPoints(g, x, y, xPos, yPos);
            if (d < 0) {
                d += 2 * xPos + 3;
            } else {
                d += 2 * (xPos - yPos) + 5;
                yPos--;
            }
            xPos++;
        }
    }

    private void drawSymmetricPoints(Graphics g, int x, int y, int xPos, int yPos) {
        g.drawLine(x + xPos, y + yPos, x + xPos, y + yPos);
        g.drawLine(x - xPos, y + yPos, x - xPos, y + yPos);
        g.drawLine(x + xPos, y - yPos, x + xPos, y - yPos);
        g.drawLine(x - xPos, y - yPos, x - xPos, y - yPos);
        g.drawLine(x + yPos, y + xPos, x + yPos, y + xPos);
        g.drawLine(x - yPos, y + xPos, x - yPos, y + xPos);
        g.drawLine(x + yPos, y - xPos, x + yPos, y - xPos);
        g.drawLine(x - yPos, y - xPos, x - yPos, y - xPos);
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        drawCircle(g, 100, 100, 50);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.add(new CircleDrawing());
        frame.setSize(300, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}