Calculator.java:

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Calculator extends JPanel implements ActionListener
{
  private JtextField Display = new JtextField("0");
  private String Button = "789/456*123-0.=+";
  private double result = 0;
  private String operator = "=";
  private boolean calculating = true;
  private boolean decimal = false;

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

  display.set.Editable(false);
  add(display, "North");

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

  for (int i = 0; i < button.length(); i++)

  {
  JButton p = new JButton(button.subsstring(i, i + 1));
  p.add(B);
  b.addActionListener(this);

  }

  add(p, "center");
  }

  public void actionPerformed(ActionEvent evt)
  {
  String cmd = evt.getActionCommand();
  if ('0' <= cmd.charAT(0) && cmd.charAT(0) <= '9' || cmd.equals("."))
  {
           System.out.println("Entered Here");

           if (calculating){
                System.out.println("Entered Calculating..." + cmd.
charAT(0));
           display.setText(cmd);

        }
       else
          display.setText(display.getTest() + cmd);
       calculating = false;
     }

     else
     {
       if (calculating)
       {
         if (cmd.equals("-"))
         {
            display.setText(cmd);
           calculating = false;
         }
         else
             operator = cmd;
       }
         else
       {
        try{
                 double x = Double.parseDouble(display.getText());
                 calculate(x);
        operator = cmd;
        calculating = false;
                }catch(NumberFormatExeption e){
                    display.setText("Illegal Number Format");
                    calculating = false;

                }
                calculating = true;

        


           }
         }
          }

          private void calculate(double n)
          {
          if (operator.equals("+"))
                result += n;
          else if (operator.equals("-"))
                result -= n;
          else if (operator.equals("*"))
                result *= n;
          else if (operator.equals("/"))
                result /= n;
          else if (operator.equals("="))
                result = n;
          display.setText("" = result);
           }

           public static viod main(String [] args)
           {
          JFrame Frame = new JFrame();
          frame.setTitle("Calculator");
          frame.setBounds(250, 250, 200, 200);
          frame.addWindowsListener(new WindowAdapter();
          {  
            public void windowClosing(WindowEvent e);
          
              } System.exit(0);
            
         }
        }

        Container contentPane = frame.getContent.Panel();
        ContentPanel.add(new Calculator());
        frame.show();
         }
  }