Graphics Demo

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

public class Demo {
  public static void main(String[] args) {
    JFrame f = new JFrame("Demo");
    f.setSize(new Dimension(500, 500));
    JPanel p = new JPanel() {
      private static final long serialVersionUID = 1L;

      @Override
      public void paintComponent(Graphics g) {
        g.setColor(Color.BLACK);
        g.drawLine(125, 0, 125, 80);
        g.drawLine(250, 0, 250, 80);
        g.drawLine(375, 0, 375, 80);
        g.drawLine(0, 80, 500, 80);
      }
    };
    f.add(p);
    f.setVisible(true);
  }
}