SimpleGui.java

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.WindowConstants;

public class SimpleGui {
    private static void createAndShowGUI() {
        // Create and set up the window.
        JFrame frame = new JFrame("HelloWorldSwing");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        // Add the ubiquitous "Hello World" label.
        JLabel label = new JLabel("Hello World");
        frame.getContentPane().add(label);

        // Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(SimpleGui::createAndShowGUI);
    }
}