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

public class Calculator
{
   public static void main(String[] args)
   {  
      CalculatorFrame frame = new CalculatorFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.show();
   }
}

class CalculatorFrame extends JFrame
{
   public CalculatorFrame()
   {
      setTitle("Calculator");
      Container contentPane = getContentPane();
      CalculatorPanel panel = new CalculatorPanel();
      contentPane.add(panel);
      pack();
   }
}

class CalculatorPanel extends JPanel
{  
   public CalculatorPanel()
   {  
      setLayout(new BorderLayout());
      panel = new JPanel();
      ActionListener listener = new CommandAction();
      JButton button = new JButton("Hello");
      button.addActionListener(listener);
      panel.add(button);  
      add(panel, BorderLayout.CENTER);
   }
  
   private class CommandAction implements ActionListener
   {
      public void actionPerformed(ActionEvent evt)
      {  
         System.out.println("Hello");
      }
   }
   
   private JLabel display;
   private JPanel panel;
   private double result;
   private String lastCommand;
 
}