New to Java

I'm trying to run a applet but I get the error:

java.lang.ClassCastException: gui.Start cannot be cast to java.applet.Applet

(if this is important I'm using eclipse)

My code is (class Line extends JPanel)

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

public class Start {

	public static void main(String[] args) {
		JFrame window = new JFrame();
		window.setSize(100, 600);
		window.setTitle("Sliding Windows");
		
		Line la = new Line (0,0,60, 300, Color.blue);
		Container c = window.getContentPane();
		c.add(la);
		window.setVisible(true);

	}

}