SwingPaintDemo

Adapted from demos in the Java Tutorial. 

import javax.swing.SwingUtilities;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.BorderFactory;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;

public class SwingPaintDemo {
   
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI(); 
            }
        });
    }

    private static void createAndShowGUI() {
        System.out.println("Created GUI on EDT? "+
        SwingUtilities.isEventDispatchThread());
        JFrame f = new JFrame("Swing Paint Demo");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(new MyPanel());
        f.pack();
        f.setVisible(true);
    }
}

class MyPanel extends JPanel {

    public MyPanel() {
        setBorder(BorderFactory.createLineBorder(Color.black));
    }

    public Dimension getPreferredSize() {
        return new Dimension(200,200);
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);       

        // Deathly Hallows Symbol
        int x[] = {10, 190, 100};
        int y[] = {190, 190, 25};
        g.drawPolygon(x, y, 3);
        g.drawOval(48 , 86 , 104, 104);
        g.drawLine(100, 190, 100, 25);

    }  
}