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

class CalculatorPanel extends JPanel
{
	  private double result;
	   private String lastCommand;

//********************   STUDENTS	****************
// calculate() is the only method you need to adjust in this file
 public void calculate(double x)
 {
   if (lastCommand.equals("=")) result = x;
       if (lastCommand.equals("+")) result += x;
	      else if (lastCommand.equals("-")) result -= x;
	      else if (lastCommand.equals("*")) result *= x;
	      else if (lastCommand.equals("/")) result /= x;
	      else if (lastCommand.equals("=")) result = x;
       /*
        * now use your DecimalToBinary class to convert
        *your result to binary
       
       */  
	      display.setText(""+  result);
	   }

	
	 
	
   public CalculatorPanel()
   {
      setLayout(new BorderLayout());

      result = 0;
      lastCommand = "=";
      start = true;

      // add the display

      display = new JButton("0");
      display.setEnabled(false);
      add(display, BorderLayout.NORTH);

      ActionListener insert = new InsertAction();
      ActionListener command = new CommandAction();

      // add the buttons in a 4 x 4 grid

      panel = new JPanel();
      panel.setLayout(new GridLayout(4, 4));

      addButton("7", insert);
      addButton("8", insert);
      addButton("9", insert);
      addButton("/", command);

      addButton("4", insert);
      addButton("5", insert);
      addButton("6", insert);
      addButton("*", command);

      addButton("1", insert);
      addButton("2", insert);
      addButton("3", insert);
      addButton("-", command);

      addButton("0", insert);
      addButton(".", insert);
      addButton("=", command);
      addButton("+", command);

      add(panel, BorderLayout.CENTER);
   }

   /**
    * Adds a button to the center panel.
    * @param label the button label
    * @param listener the button listener
    */
   private void addButton(String label, ActionListener listener)
   {
      JButton button = new JButton(label);
      button.addActionListener(listener);
      panel.add(button);
   }

   /**
    * This action inserts the button action string to the end of the display text.
    */
   private class InsertAction implements ActionListener
   {
      public void actionPerformed(ActionEvent event)
      {
         String input = event.getActionCommand();
         if (start)
         {
            display.setText("");
            start = false;
         }
         display.setText(display.getText() + input);
      }
   }

   /**
    * This action executes the command that the button action string denotes.
    */
   private class CommandAction implements ActionListener
   {
      public void actionPerformed(ActionEvent event)
      {
         String command = event.getActionCommand();

         if (start)
         {
            if (command.equals("-"))
            {
               display.setText(command);
               start = false;
            }
            else lastCommand = command;
         }
         else
         {
            calculate(Double.parseDouble(display.getText()));
            lastCommand = command;
            start = true;
         }
      }
   }

  
   private JButton display;
   private JPanel panel;
    private boolean start;


}

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


public class Calculator
{
   public static void main(String[] args)
   {
      EventQueue.invokeLater(new Runnable()
         {
            public void run()
            {
               CalculatorFrame frame = new CalculatorFrame();
               frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
               frame.setVisible(true);
            }
         });
   }



}