public class FertilizerGraph extends JComponent implements Observer {
	
	public void paintComponent(Graphics g){
		
		Graphics2D g2 = (Graphics2D) g;
		Rectangle box = new Rectangle(5,10,10,30);
		g2.draw(box);
	}
	
	public void update(Observable o, Object a){
		
	}
}


//in my gui class constructor

		FertilizerGraph fertgraph = new FertilizerGraph();
		f.getContentPane().add(fertgraph, BorderLayout.CENTER);