public void paintComponent(Graphics g) {
    Graphics2D g2d = (Graphics2D) g.create();
    g2d.setStroke(new BasicStroke(1.0f));

    if (isOpaque()) {
      g2d.setColor(getBackground());
      g2d.fillRect(0, 0, getWidth(), getHeight());
    }

    g2d.setColor(Color.black);
    g2d.drawLine(0, frameHeight / 2, frameWidth, frameHeight / 2);
    g2d.drawLine(frameWidth / 2, 0, frameWidth / 2, frameHeight);

    for (int i = unityX; i < frameWidth / 2; i += unityX) {
      g2d.drawLine(
          frameWidth / 2 + i, frameHeight / 2 - 3, frameWidth / 2 + i, frameHeight / 2 + 3);
      g2d.drawLine(
          frameWidth / 2 - i, frameHeight / 2 - 3, frameWidth / 2 - i, frameHeight / 2 + 3);
    }

    for (int i = unityY; i < frameHeight / 2; i += unityY) {
      g2d.drawLine(
          frameWidth / 2 - 3, frameHeight / 2 + i, frameWidth / 2 + 3, frameHeight / 2 + i);
      g2d.drawLine(
          frameWidth / 2 - 3, frameHeight / 2 - i, frameWidth / 2 + 3, frameHeight / 2 - i);
    }

    g2d.setColor(Color.blue);
    function.drawFunctionToGraphic(g2d, frameWidth, frameHeight, unityX, unityY);

    paintCurrentMethodState(g2d);

    g2d.dispose();
  }