import javax.swing.JFrame;
import java.awt.event.WindowListener;
import java.awt.event.WindowEvent;

class Program01 extends JFrame {
	Program01() {
		
		addWindowListener(new WindowListener(){
			public void windowDeactivated(WindowEvent event) {}
			public void windowActivated(WindowEvent event) {}
			public void windowDeiconified(WindowEvent event) {}
			public void windowIconified(WindowEvent event) {}
			public void windowClosed(WindowEvent event) {}
			public void windowClosing(WindowEvent event) {}
			public void windowOpened(WindowEvent event) {}
		});	
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setSize(400, 300);
		centerWindow(this);
		setVisible(true);
	}
	public static void centerWindow(java.awt.Window frame) {
		java.awt.Dimension dimension = 
                      java.awt.Toolkit.getDefaultToolkit().getScreenSize();
		int x = (int) ((dimension.getWidth() - frame.getWidth()) / 2);
		int y = (int) ((dimension.getHeight() - frame.getHeight()) / 2);
		frame.setLocation(x, y);
	}	
	public static void main(String[] args) {
		new Program01();
	}
}