[hardwired]

Code:

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

public class L6D{
	public static void main(String[] args) throws Exception{
		Grid frame = new Grid();
		frame.setTitle("Lab6 - Application #1");
		frame.setSize(400,300);
		frame.setVisible(true);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setLocationRelativeTo(null);
	}
}

class Grid extends JFrame{
	public Grid(){
		Color[] bgColors = {
			new Color(50,100,75), Color.red,
			Color.green.darker(), Color.blue
		};
		Color[] fgColors = {
			Color.orange, Color.blue,
			Color.yellow, Color.red
		};
		JPanel panel = new JPanel();
		panel.setLayout(new GridLayout(2,2,1,1));
		for(int j = 0; j < bgColors.length; j++) {
			panel.add(new NewPanel(bgColors[j], fgColors[j]));
		}

		this.add(panel);
	}
}

class NewPanel extends JPanel implements MouseListener{
	Color color;
	public int x1= 0;
	public int y1= 0;
	public int x2= -1;
	public int y2= -1;

	public NewPanel(Color bg, Color fg){
		setBackground(bg);
		color = fg;
		// Register listener for the mouse event
		addMouseListener(this);
	}

	public void mouseClicked(MouseEvent e) {}
	public void mouseEntered(MouseEvent e) {}
	public void mouseExited(MouseEvent e) {}
	public void mouseReleased(MouseEvent e) {}

	public void mousePressed(MouseEvent e) {
		if (x1 != x2 || y1 != y2){
		   	x1 = e.getX();
		   	y1 = e.getY();
			x2 = x1;
			y2 = y1;
		} else {
			x2 = e.getX();
			y2 = e.getY();
		}
		repaint();
	}

  	protected void paintComponent(Graphics g){
		super.paintComponent(g);
		g.setColor(color);
		g.drawLine(x1,y1,x2,y2);
	}
}