How to get rid of flickering when opening Java window?

Question

Java

The opening frame gets annoying with its flickering when centered. Here is the code for a simple program.
Main.java

import javax.swing.*;

public class Main extends JFrame {

    public static void main(String[] args) {
        JFrame frame = new JFrame("Тест фрейма");
        frame.add(new MainMenu());
        frame.setSize(600, 400);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        frame.setResizable(false); 
        frame.setLocationRelativeTo(null); //из-за него мерцает???
    }

Then he opens a window, it appears for a millisecond in the upper left corner, and then moves to the center!

Answer 1

The main mistake is that all your code needs to be wrapped:

SwingUtilities.invokeLater(new Runnable() {
// TODO
})

Read about EventDispatchThread in Swing.

Answer 2

And you can try setDoubleBuffered(true);
But, of course, you need to launch the window in the interface processing thread.

Answer 3

You need to move setVisible to the very end.
And there is also a bug in the JDK about flickering in swing. But this way you at least minimize it.