CenteredFrame

import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JFrame;

public class CenteredFrame extends JFrame {
public CenteredFrame() {
setTitle("CenteredFrame");
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
Toolkit tk = Toolkit.getDefaultToolkit();
Dimension screenSize = tk.getScreenSize();
int screenHeight = screenSize.height;
int screenWidth = screenSize.width;
setSize(screenWidth / 2, screenHeight / 2);
setLocation(screenWidth / 4, screenHeight / 4);
}

public static void main(String[] args) {
JFrame frame = new CenteredFrame();
frame.show();
}
}