To Set window in the middle of screen

import java.awt.Dimension;
import java.awt.Toolkit;

import javax.swing.JFrame;

public class Main {
public static void main(String[] argv) throws Exception {
Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();

JFrame window = new JFrame();
window.setSize(300,300);

int w = window.getSize().width;
int h = window.getSize().height;
int x = (dim.width - w) / 2;
int y = (dim.height - h) / 2;

window.setLocation(x, y);

window.setVisible(true);
}
}