Draw2 (you don't want Draw1)

File: java/Draw2/Main.java

/*
 * Drawing in a Canvas
 * RIGHT WAY -- Does drawing in a callback
 * R. Jacob  9/18/2001
 */

// Can import whole packages this way
import java.awt.*;
import javax.swing.*;

public class Main extends JFrame {
    public static void main (String [] args) {
	new Main ();
    }

    public Main () {
	// Window setup
	setSize (300, 300);
	Container content = getContentPane();
	
	// Put a Canvas in
	MyCanvas canvas = new MyCanvas ();
	content.add (canvas);
    
	// Show the window
	setVisible (true);
    }
}

File: java/Draw2/MyCanvas.java

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

public class MyCanvas extends JComponent {
    // This is the draw callback
    // N.B. component is automatically cleared first
    public void paintComponent (Graphics g) {
	g.drawLine (50, 50, 100, 50);
    }
}