import java.awt.Graphics;
import javax.swing.JPanel;


public class GraphCanvas extends JPanel
{
   private IDrawable _drawing = NullDrawable.Singleton;

	public void setDrawable(IDrawable drawing)
   {
      _drawing = drawing;
   }

   public void paintComponent (Graphics g)
   {
      super.paintComponent (g);
      _drawing.draw (g);
   }
}