public class DialogD extends JDialog {
    private JButton pbHideMe = new JButton("Hello DIALOG !!, Close ME");

    public DialogD() {
        this.setTitle("Dialog D Here");
        this.setModal(true);
        this.getContentPane().add(pbHideMe);
        pbHideMe.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                DialogD.this.setVisible(false);
            }
        })
        pbHitMe.setPreferredSize(new Dimension(100,100));
        this.pack();
    }
}


public class FormA extends JFrame {
    private JButton pbHitMe = new JButton("Hello FORM !!, Hit Me");
    public FormA() {
        this.setTitle("Form A Here");
        this.getContentPane().add(pbHitMe);
        pbHitMe.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                DialogD dd = new DialogD();
                dd.setVisible(true);
            }
        });
        pbHitMe.setPreferredSize(new Dimension(100,100));
        this.pack();
    }
}


public class RunMe {
    public static void main(String[] args) {
        FormA fa = new FormA();
        fa.setVisible(true);
    }
}