// Write an applet that displays 8 by 8 grid. When clicking on an empty 
// square, a filled rectangle is displayed. When clicking on the filled
// square, the filled rectangle there disappears. Illustrates MouseListener
// and adapter classes. 

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

public class QueensApplet extends JApplet {

   private boolean [][] board = new boolean [8][8];
   private Container contentPane;

   public void init () {

	contentPane = getContentPane();
	contentPane.setBackground(Color.white);
	
	// initialize the board array

	for (int i = 0; i < 8; i++) 
	   for (int j = 0; j < 8; j++)
	      board[i][j] = false;

	addMouseListener (new BoardMouseListener ());

   }

   public void paint (Graphics g) {

	super.paint(g);

	// draw the board's vertical lines

	g.drawLine (0, 0, 0, 400);
	g.drawLine (50, 0, 50, 400);
	g.drawLine (100, 0, 100, 400);
	g.drawLine (150, 0, 150, 400);
	g.drawLine (200, 0, 200, 400);
 	g.drawLine (250, 0, 250, 400);
 	g.drawLine (300, 0, 300, 400);
	g.drawLine (350, 0, 350, 400);
  	g.drawLine (400, 0, 400, 400);

	// draw the board's horizontal lines

	g.drawLine (0, 0, 400, 0);
	g.drawLine (0, 50, 400, 50);
	g.drawLine (0, 100, 400, 100);
	g.drawLine (0, 150, 400, 150);
	g.drawLine (0, 200, 400, 200); 
 	g.drawLine (0, 250, 400, 250);
 	g.drawLine (0, 300, 400, 300);
	g.drawLine (0, 350, 400, 350);
  	g.drawLine (0, 400, 400, 400);

	for (int i = 0; i < 8; i++)
	   for (int j = 0; j < 8; j++)
	      if (board[i][j])
		 g.fillRect(50*i, 50*j, 50, 50);  
   }


   private class BoardMouseListener extends MouseAdapter {

	public void mouseClicked (MouseEvent e) {

	   // get coordinates of the mouse click

	   int x_coord = e.getX ();
	   int y_coord = e.getY ();

	   // convert x_coord and y_coord into board's row and column #'s

	   int row = x_coord/50;
	   int column = y_coord/50;

	   board[row][column] = !board[row][column];

	   repaint();
	}
   }
}