import java.awt.*;
import javax.swing.*;
public class test {
    public static void main(String[] args) {
	testFrame frame = new testFrame();
	frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	frame.show();
    }
}
 
/**
   A frame that contains a message panel
*/
class testFrame extends JFrame
{
    public testFrame() {
	setTitle("test");
	setSize(WIDTH, HEIGHT);
	//add panel to frame
	testPanel panel = new testPanel();
	Container contentPane = getContentPane();
	contentPane.add(panel);
	new Thread(panel).start();
    }
    public static final int WIDTH = 400;
    public static final int HEIGHT = 300;
}
 
/**
   A panel that displays a message
*/
class testPanel extends JPanel implements Runnable
{
    int flag = 1;
    public void paintComponent(Graphics g) {
	super.paintComponent(g);
 
	if (flag == 1)
	    g.setColor(Color.BLUE);
	else
	    g.setColor(Color.yellow);
	g.drawString("test", MESSAGE_X, MESSAGE_Y);
    }
    
    public void run() {
	try {
	    while(true){
		flag = -flag;
		Thread.sleep(250);
		repaint();
	    }
	}
	catch (InterruptedException e) {
	}
    }
 
    public static final int MESSAGE_X = 75;
    public static final int MESSAGE_Y = 100;
}