import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.Random;
public class RandomWalkX extends JPanel implements ActionListener {

    JButton b = new JButton("Start");
    int size = 400;
    int xpos = size/2, ypos = size/2;
    int step = 15;
    Random random = new Random();
    Timer timer;
    boolean still = true;

    public RandomWalkX () {
	setBackground(Color.white);
	add(b);
	b.addActionListener(new ActionListener() {            // the ActionListner
		public void actionPerformed(ActionEvent e){   // for the button
		    if (still){                               // is an anonymous
			timer.start();                        // inner class
			b.setText("Stop");
		    }
		    else{
			timer.stop();
			b.setText("Start");
		    }
		    still = !still;
		}});
	
	timer = new Timer(100,this);
    }


    public void actionPerformed(ActionEvent e) {     // for Timer-driven movement
	xpos += random.nextInt(step)-step/2;
	ypos += random.nextInt(step)-step/2;
	repaint();
    }


    public void paintComponent (Graphics g) {
	super.paintComponent(g);
	g.setColor(Color.magenta);
        g.fillOval(xpos, ypos, 10, 10);
    }

    public static void main(String[] u) {
	JFrame f = new JFrame();
	f.setSize(400, 400);
	f.add(new RandomWalkX());
	f.setVisible(true);
	f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}