import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JWindow;
import javax.swing.SwingUtilities;

public class FensterTypen {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new FrameFenster());
        SwingUtilities.invokeLater(() -> new WindowFenster());
        SwingUtilities.invokeLater(() -> new DialogFenster());
    }
}

class FrameFenster {
    public FrameFenster() {
        JFrame frame = new JFrame("JFrame-Fenster");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 300);
        frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
        frame.setLocationRelativeTo(null);
        frame.add(new JLabel("JFrame-Fenster"));
        frame.setVisible(true);
    }
}

class WindowFenster {
    public WindowFenster() {
        JWindow window = new JWindow();
        window.setSize(300, 300);
        window.setLocation(100, 100);
        window.add(new JLabel("JWindow-Fenster"));
        window.setVisible(true);
    }
}

class DialogFenster {
    public DialogFenster() {
        JDialog dialog = new JDialog();
        dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
        dialog.setSize(300, 300);
        dialog.setLocation(300, 200);
        dialog.setTitle("JDialog-Fenster");
        dialog.add(new JLabel("JDialog-Fenster"));
        dialog.setVisible(true);
    }
}