package gui;


import javax.swing.JFrame;
import javax.swing.JPanel;

public class MainScreen extends JFrame
{
public MainScreen() throws IOException
{
....
    this.pack();
    this.setVisible(true);
}
}

public static void main(String[] args)
{
    //avoid blocking the main thread
    SwingUtilities.invokeLater(new Runnable(){
        @Override
        public void run() {

            try {

                new MainScreen();
            } catch (IOException e) {
                e.printStackTrace();
            };
        }
    });


}