// The "EventDemo" class.
import java.applet.*;
import java.awt.*;
import java.awt.event.*;



public class EventDemo extends Applet
{
    private Button left, right;//declare two buttons
    private Display demoDisplay;//declare a display object
    
    
    public void init ()
    {
	setLayout(new BorderLayout() );//set up the screen layout
	demoDisplay = new Display();//initialize a new display object
	add(BorderLayout.CENTER, demoDisplay);//place the display in the center of the layout
	
	Panel p = new Panel();//initialize a panel
	left = new Button("Left");//initialize the left button
	p.add(left);//add the button to the panel
	
	right = new Button("Right");//initialize the right button
	p.add(right);//add the right button to the panel
	
	add(BorderLayout.SOUTH, p);//add the panel to the layout
	
	left.addActionListener(demoDisplay);//allow the left button to receive clicks
	right.addActionListener(demoDisplay);//allow the right button to receive clicks
    } // init method
}
    
class Display extends Canvas implements ActionListener
//a user defined class to set up a display
{
    private Point center;//declare a point
    
    public Display()
    {
	center = new Point(50,50);//initialize the point
	setBackground(Color.white);
    }


    public void actionPerformed(ActionEvent e)
    {
	String direction = e.getActionCommand();//accept an external action command
	
	if (direction.equals("Left") )
	{
	    center.x = center.x - 20;//change the position of the point toward the left
	}
	else if (direction.equals("Right") )
	{
	    center.x = center.x + 20;//toward the right
	}
	
	repaint();//refresh the screen
      }
    
    public void paint (Graphics g)
    {
	g.setColor(Color.red);
	g.fillOval(center.x - 5, center.y = 5, 10, 10);//draw an oval.  This is a circle because the coordinates are
				    //the same
    } // paint method
} // EventDemo class