Simple Example Draw a Rectangle using mouse

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

public class DrawRectRx extends JPanel
{
private int pointCount =0;
private Point points[] = new Point[100];
private Point points2[] = new Point[100];
private Point start = new Point();
private Point end = new Point();
Rectangle rect = new Rectangle();

public DrawRectRx()
{
addMouseMotionListener( new MouseMotionAdapter()
{
public void mouseDragged(MouseEvent ev)
{
end = ev.getPoint();
rect.setFrameFromDiagonal(start, end);
repaint();
}//end mouse drag
});
addMouseListener(new MouseAdapter()
{
public void mousePressed(MouseEvent e)
{
start = e.getPoint();
}

public void mouseReleased(MouseEvent ev)
{
points[pointCount] = start;
points2[pointCount] = ev.getPoint();
pointCount++;
rect.setFrameFromDiagonal(start, start);
repaint();
}
});
}

protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
// Draw line being dragged.
g2.setPaint(Color.red);
g2.draw(rect);
// Draw lines between points in arrays.
g2.setPaint(Color.blue);
Rectangle r = new Rectangle();
for (int i =0; i < pointCount; i++)
{
r.setFrameFromDiagonal(points[i], points2[i]);
g2.fill(r);
}
}

public static void main(String[] args)
{
DrawRectRx test = new DrawRectRx();
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(test);
f.setSize(400,400);
f.setLocation(200,200);
f.setVisible(true);
}
}