如何使用图形 2D 绘制功能图？

Question

我创建类：

class DrawGraph extends Jpanel{
@Override
public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;

        for (int i = 0; i <= 600; i += 30) {
            g2d.setStroke(new BasicStroke(1));
            g2d.setColor(Color.GRAY);
            g2d.drawLine(i, 0, i, 600);
            g2d.drawLine(0, i, 600, i);
        }
        for (int i = 60; i < 600; i += 60) {
            if (i != 300) {
                g2d.setStroke(new BasicStroke(2f));
                g2d.setColor(Color.BLACK);
                g2d.drawLine(i + 1, 297, i + 1, 303);
                g2d.drawString(String.valueOf((300 - i) / 60 * -1), i - 2, 295);
                g2d.drawLine(297, i + 1, 303, i + 1);
                g2d.drawString(String.valueOf((300 - i) / 60), 303, i - 2);
            }
        }
        g2d.setColor(Color.BLUE);
        g2d.drawString("y", 315, 15);
        g2d.drawString("x", 585, 285);
        g2d.setStroke(new BasicStroke(2f));
        g2d.setColor(Color.BLACK);
        g2d.drawLine(300, 0, 300, 600);
        g2d.drawLine(0, 300, 600, 300);
    }
}

结果：

但现在我不知道如何继续将 Math 函数绘制到这个图上。我可以使用 2 个班级在 1 个面板中绘画吗？