Java Swing Draw Rectangles

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

public class DrawRectangle extends JPanel {
  public void paint(Graphics g) {
    Graphics2D g2 = (Graphics2D) g;
    g2.setPaint(Color.red);
    int x = 40;
    int y = 40;
    Rectangle2D.Double rect1=new Rectangle2D.Double(x, y, 150, 100);
    Rectangle2D.Double rect2=new Rectangle2D.Double(x, y, 200, 100);
    Rectangle2D.Double rect3=new Rectangle2D.Double(x, y, 250, 100);
    g2.draw(rect1);
    g2.draw(rect2);
    g2.draw(rect3);
    }

  public static void main(String[] args) {
    JFrame frame = new JFrame();
    frame.setTitle("Show Different Polygons");
    frame.setSize(350, 250);
    Container contentPane = frame.getContentPane();
    contentPane.add(new DrawRectangle());
    frame.show();
  }
}