DialogoLayouts

public class Dialogo extends JDialog {
        public int filas;
        public int columnas;

    public Dialogo(Frame parent) {
        super(parent, "Nivel de dificultad");
        setVisible(true);
        setSize(400,400);
        setLocationRelativeTo(null);
        componentes();
        revalidate();
    }

    private JFrame componentes() {
        JFrame compos = new JFrame();
        compos.setLayout(new BorderLayout());
        compos.add(radioButtons(), BorderLayout.PAGE_START);
        compos.add(textAreas(), BorderLayout.CENTER);
        return compos;
    }

    private JPanel radioButtons() {
        JPanel rButtons = new JPanel();
        setLayout(new FlowLayout());
        JRadioButton easyMode = new JRadioButton("Fácil");
        add(easyMode);
        JRadioButton mediumMode = new JRadioButton("Medio");
        add(mediumMode);
        JRadioButton hardMode = new JRadioButton("Difícil");
        add(hardMode);
        JRadioButton customMode = new JRadioButton("Personalizado");
        add(customMode);
        ButtonGroup bgModes = new ButtonGroup();
        bgModes.add(easyMode);
        bgModes.add(mediumMode);
        bgModes.add(hardMode);
        bgModes.add(customMode);
        return rButtons;
    }

    private JPanel textAreas() {
        JPanel textAreas = new JPanel();
        // Aquí iría otro Layout distinto textAreas.setLayout(new FlowLayout());
        JTextField txtFilas = new JTextField();
        txtFilas.setBounds(10, 110, 200, 40);
        add(txtFilas);
        JLabel lbFilas = new JLabel("Filas");
        lbFilas.setBounds(10, 110, 200, 40);
        add(lbFilas);
        return textAreas;
    }