JDialog

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;


/**
 *
 * @author  Bruno
 */
public class MessageClass {
    
    private JFrame frame = new JFrame("Exemplo botao");
    
    private void showMessage(String message, Component parent, String title){
        JOptionPane.showMessageDialog(parent, message, title, JOptionPane.ERROR_MESSAGE);
    }
    
    public MessageClass(){
        
        JButton botao1 = new JButton("Adicionar");
        botao1.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent a){
                showMessage("Teste Inserir",frame, "Botao Inserir");
            }
        });
        
        JButton botao2 = new JButton("Remover");
        botao2.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent a){
                showMessage("Teste remover",frame, "Botao Remover");
            }
        });
        
        frame.getContentPane().add(botao1, BorderLayout.NORTH);
        frame.getContentPane().add(botao2, BorderLayout.CENTER);
        
        frame.show();
        
    }
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        MessageClass aMessageClass = new MessageClass();
    }
}

class PantsViewer extends JPanel{
   public static final int OK_OPTION = 0;
   public static final int CANCEL_OPTION = 1;

   private int lastSelectedOption;

   private JTextField name;
   private JTextArea description;
   private JSlider size;
   private JComboBox color;
   private JButton okButton;
   private JButton cancelButton;
   ...

   public void setPants(Pants pants);
   public Pants getPants();

   public int getLastSelectedOption() {
    return lastSelectedOption;
   }
}

interface Pants {
   public String getName();
   public void setName(String name);
   public String getDescription();
   public void setDescription(String description);
   public int getSize();
   public void setSize(int size);
   public Color getColor();
   public void setColor(Color color);
}

class PantsImpl implements Pants {
   ...
}

// código da janela:
Pantsviewer pantsViewer = new PantsViewer();
JDialog d = new JDialog("Pants");
d.add();
...

// código que mostra a tela:
pantsViewer.setPants();
pantsViewer.getParentComponent().show(); // isso é feio, mas não quero entrar em detalhes
if (pantsViewer.getLastSelectedOption() == PantsViewer.OK_OPTION) {
  Pants p = pantsViewer.getPants();
  someguy.firePantsChanged(p);
}

public Pants getPants() {
  Pants p = new PantsImpl();
  p.setName(name.getText());
  p.setDescription(description.getText());
  ...
  return p;
}