Minimal Swing Frame

MinSampleFrame.java

import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class MinSampleFrame {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Test");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(...);
        SwingUtilities.invokeLater(() -> {
            frame.pack();
            frame.setVisible(true);
        });
    }
}