Why is my JFrame size smaller than the size that I input into setPreferredSize()?-CodePudding

I have tried running the following code. The GUI constructor that I call is from a class that extends JPanel.

As you can see I have already tried using the pack() method.

The window that appears is smaller than 500x500. How do I fix this?

import java.awt.Dimension;
import javax.swing.JFrame;

public class Main extends JFrame {

    public Main(){


        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);

        setPreferredSize(new Dimension(500, 500));

        setTitle("Chess");
        
        GUI gui = new GUI();
        setContentPane(gui);

        pack();

        setVisible(true);

    }



    public static void main(String[] args){

        Main main = new Main();
        main.repaint();
    }

Already tried using pack().

CodePudding user response：

Because the frame size includes the frame borders, title bars, and headers which are especially large and take up extra space. Set the size of a JPanel and add that to the frame and draw and add components to the panel. And don't forget to call frame.pack().