Draw a grid by drawing lines in Java

/* w  w  w . j a  va2 s .c om*/
import java.awt.Graphics;

import javax.swing.JComponent;
import javax.swing.JFrame;

class MyCanvas extends JComponent {
  public void paint(Graphics g) {

    int rows = 20;

    int cols = 30;
    int width = getSize().width;
    int height = getSize().height;

    // draw the rows
    int rowHt = height / (rows);
    for (int i = 0; i < rows; i++)
      g.drawLine(0, i * rowHt, width, i * rowHt);

    // draw the columns
    int rowWid = width / (cols);
    for (int i = 0; i < cols; i++)
      g.drawLine(i * rowWid, 0, i * rowWid, height);

  }
}

public class Main {
  public static void main(String[] a) {
    JFrame window = new JFrame();
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    window.setBounds(30, 30, 450, 450);
    window.getContentPane().add(new MyCanvas());
    window.setVisible(true);
  }
}