import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JPanel;

public class MyPanel extends JPanel {
	private int x = -1;
	private int y = -1;

	public MyPanel() {
		this.addMouseListener(new MouseAdapter() {
			// Anonymous class.
			public void mouseClicked(MouseEvent e) {
				// Check whether the left mouse button is clicked
				if (e.getButton() == MouseEvent.BUTTON1) {
					x = e.getX();
					y = e.getY();
					// get the coordinate
					System.out.println("(" + e.getX() + "," + e.getY() + ")");
					// force Swing to repaint the red point
					repaint();
				}

			}
		});
	}

	@Override
	protected void paintComponent(Graphics g) {
		// must clean the panel before drawing on it.
		super.paintComponent(g);
		g.setColor(Color.RED);
		// draw the red square
		g.drawRect(x, y, 1, 1);
	}
}