[hardwired]

Code:

import java.awt.*;
import java.awt.geom.Line2D;
import javax.swing.*;

public class CreateGridRx extends JPanel {
    int gridSize;
    final int PAD = 20;

    public CreateGridRx(int size) {
        this.gridSize = size;
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        int w = getWidth();
        int h = getHeight();
        double xInc = (double)(w - 2*PAD)/gridSize;
        double yInc = (double)(h - 2*PAD)/gridSize;
        for(int j = 0; j <= gridSize; j++) {
            double x = PAD + j*xInc;
            g2.draw(new Line2D.Double(x, PAD, x, h-PAD));
        }
        for(int j = 0; j <= gridSize; j++) {
            double y = PAD + j*yInc;
            g2.draw(new Line2D.Double(PAD, y, w-PAD, y));
       }
    }

    public static void main(String[] args) {
        String input = JOptionPane.showInputDialog(
                "Enter number of rows and columns you want grid to contain\n" +
                "(For example entering 2 will create a 2x2 grid)\n");
        int gridSquares = Integer.parseInt( input ); 
        CreateGridRx test = new CreateGridRx(gridSquares);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(test);
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}