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

class CalculatorDemo extends JPanel implements ActionListener {
  JButton ButtonNumber[] = new JButton[10];
  JButton ButtonAdd, ButtonSubtract, ButtonMul, ButtonDivind;
  JButton ButtonPoint, ButtonEqual;
  JButton ButtonMC, ButtonMR, ButtonMSub, ButtonMplus;
  JButton ButtonSqrt, ButtonPercent, ButtonInvert, ButtonNega;
  JButton ButtonCE, ButtonBackspace, ButtonClear;
  JButton ButtonOFF;
  JTextField TextFieldTitle;
  JLabel LabelNull;
  String Operator = null;
  int stateTextField = 1;
  double Operand1 = 0.0;
  double ans = 0.0;
  double M = 0.0;

  CalculatorDemo() {
    setLayout(new BorderLayout());
    ButtonAdd = new JButton("+");
    ButtonSubtract = new JButton("-");
    ButtonMul = new JButton("*");
    ButtonDivind = new JButton("/");
    ButtonPoint = new JButton(".");
    ButtonEqual = new JButton("=");
    ButtonClear = new JButton("Clear");
    ButtonCE = new JButton("CE");
    ButtonBackspace = new JButton("Backspace");
    ButtonMC = new JButton("MC");
    ButtonMR = new JButton("MR");
    ButtonMSub = new JButton("M-");
    ButtonMplus = new JButton("M+");
    ButtonSqrt = new JButton("sqrt");
    ButtonPercent = new JButton("%");
    ButtonInvert = new JButton("1/x");
    ButtonNega = new JButton("+/-");
    ButtonOFF = new JButton("OFF");
    for (int i = 0; i < 10; i++) {
      ButtonNumber[i] = new JButton("" + i);
    }
    LabelNull = new JLabel("");
    TextFieldTitle = new JTextField("0");
    TextFieldTitle.setHorizontalAlignment(JTextField.RIGHT);
    TextFieldTitle.setEditable(false);
    TextFieldTitle.setBackground(Color.white);
    TextFieldTitle.setForeground(Color.red);

    add(TextFieldTitle, BorderLayout.NORTH);
    add(getCompenent1(), BorderLayout.CENTER);
    add(getComponent2(), BorderLayout.SOUTH);

    for (int i = 0; i < ButtonNumber.length; i++) {
      ButtonNumber[i].addActionListener(this);
    }

    ButtonAdd.addActionListener(this);
    ButtonSubtract.addActionListener(this);
    ButtonMul.addActionListener(this);
    ButtonDivind.addActionListener(this);
    ButtonPoint.addActionListener(this);
    ButtonEqual.addActionListener(this);
    ButtonClear.addActionListener(this);
    ButtonCE.addActionListener(this);
    ButtonBackspace.addActionListener(this);
    ButtonMC.addActionListener(this);
    ButtonMR.addActionListener(this);
    ButtonMSub.addActionListener(this);
    ButtonMplus.addActionListener(this);
    ButtonSqrt.addActionListener(this);
    ButtonPercent.addActionListener(this);
    ButtonInvert.addActionListener(this);
    ButtonNega.addActionListener(this);
    ButtonOFF.addActionListener(this);
  }    //End Constructor
  JPanel getCompenent1() {
    JPanel p = new JPanel(new GridLayout(1, 5, 3, 3));
    p.add(ButtonOFF);
    p.add(LabelNull);
    p.add(ButtonBackspace);
    p.add(ButtonCE);
    p.add(ButtonClear);
    return p;
  }  // End Method getComponent

  JPanel getComponent2() {
    JPanel p = new JPanel(new GridLayout(4, 6, 3, 3));
    p.add(ButtonMC);
    p.add(ButtonNumber[7]);
    p.add(ButtonNumber[8]);
    p.add(ButtonNumber[9]);
    p.add(ButtonDivind);
    p.add(ButtonSqrt);
    p.add(ButtonMR);
    p.add(ButtonNumber[4]);
    p.add(ButtonNumber[5]);
    p.add(ButtonNumber[6]);
    p.add(ButtonMul);
    p.add(ButtonPercent);
    p.add(ButtonMSub);
    p.add(ButtonNumber[1]);
    p.add(ButtonNumber[2]);
    p.add(ButtonNumber[3]);
    p.add(ButtonSubtract);
    p.add(ButtonInvert);
    p.add(ButtonMplus);
    p.add(ButtonNumber[0]);
    p.add(ButtonPoint);
    p.add(ButtonEqual);
    p.add(ButtonAdd);
    p.add(ButtonNega);
    return p;
  }    // End Method getComponent

  public void actionPerformed(ActionEvent e) {
    if (e.getSource() == ButtonNumber[0]) {
      if (TextFieldTitle.getText().length() == 1 && TextFieldTitle.getText().equals("0")) {
        TextFieldTitle.setText("0");
      }
      else if (stateTextField == 1) {
        TextFieldTitle.setText(TextFieldTitle.getText() + "0");
      } else {
        TextFieldTitle.setText("0");
        stateTextField = 1;
      }
    } else {
      for (int i = 1; i < 10; i++) {
        if (e.getSource() == ButtonNumber[i]) {
          if (TextFieldTitle.getText().equals("0")) {
            TextFieldTitle.setText("" + i);
          }
          else if (stateTextField == 1) {
            TextFieldTitle.setText(TextFieldTitle.getText() + i);
          } else {
            TextFieldTitle.setText("" + i);
            stateTextField = 1;
          }
        }
      }
    }
    if (e.getSource() == ButtonPoint) {
      if (TextFieldTitle.getText().length() == 1) {
        TextFieldTitle.setText(TextFieldTitle.getText() + ".");
      } else {
        TextFieldTitle.setText(TextFieldTitle.getText() + "0");
      }
    }
    else if (e.getSource() == ButtonAdd) {
      Operand1 = Double.parseDouble(TextFieldTitle.getText());
      Operator = "+";
      stateTextField = 2;
    }
    else if (e.getSource() == ButtonSubtract) {
      Operand1 = Double.parseDouble(TextFieldTitle.getText());
      Operator = "-";
      stateTextField = 2;
    }
    else if (e.getSource() == ButtonMul) {
      Operand1 = Double.parseDouble(TextFieldTitle.getText());
      Operator = "*";
      stateTextField = 2;
    }
    else if (e.getSource() == ButtonDivind) {
      Operand1 = Double.parseDouble(TextFieldTitle.getText());
      Operator = "/";
      stateTextField = 2;
    }
    else if (e.getSource() == ButtonPercent) {
      Operand1 = Double.parseDouble(TextFieldTitle.getText());
      Operator = "%";
      stateTextField = 2;
    }
    else if (e.getSource() == ButtonSqrt) {
      Operand1 = Double.parseDouble(TextFieldTitle.getText());
      TextFieldTitle.setText(Double.toString(Math.sqrt(Operand1)));
      stateTextField = 2;
    }
    else if (e.getSource() == ButtonInvert) {
      Operand1 = Double.parseDouble(TextFieldTitle.getText());
      TextFieldTitle.setText(Double.toString(1 / Operand1));
      stateTextField = 2;
    }
    else if (e.getSource() == ButtonNega) {
      Operand1 = Double.parseDouble(TextFieldTitle.getText());
      TextFieldTitle.setText(Double.toString(-1 * Operand1));
      stateTextField = 2;
    }
    else if (e.getSource() == ButtonEqual) {
      if (Operator != null) {
        ans = answer(Operand1, Operator, Double.parseDouble(TextFieldTitle.getText()));
        TextFieldTitle.setText(Double.toString(ans));
        Operator = null;
      }
    }
    else if (e.getSource() == ButtonClear) {
      Operator = null;
      TextFieldTitle.setText("0");
      stateTextField = 1;
    }
    else if (e.getSource() == ButtonCE) {
      TextFieldTitle.setText("0");
      stateTextField = 1;
    }
    else if (e.getSource() == ButtonMplus) {
      double z = Double.parseDouble(TextFieldTitle.getText());
      M = M + z;
      Operator = null;
      stateTextField = 2;
    }
    else if (e.getSource() == ButtonMSub) {
      double z = Double.parseDouble(TextFieldTitle.getText());
      M = M - z;
      Operator = null;
      stateTextField = 2;
    }
    else if (e.getSource() == ButtonMR) {
      TextFieldTitle.setText(Double.toString(M));
    }
    else if (e.getSource() == ButtonMC) {
      M = 0;
      stateTextField = 1;
    }
    else if (e.getSource() == ButtonOFF) {
      System.exit(3);
    }
    if (e.getSource() == ButtonBackspace) {
      if (!TextFieldTitle.getText().equals("0") && !TextFieldTitle.getText().equals(null)) {
        String S = TextFieldTitle.getText();
        int num = S.length();
        if (num != 1) {
          String S2 = S.substring(0, num - 1);
          TextFieldTitle.setText(S2);
        } else {
          TextFieldTitle.setText("0");
        }
      }
    }
  }
  double answer(double O1, String Operator, double O2) {
    if (Operator.equals("+")) {
      return O1 + O2;
    }
    else if (Operator.equals("-")) {
      return O1 - O2;
    }
    else if (Operator.equals("*")) {
      return O1 * O2;
    }
    else if (Operator.equals("/")) {
      return O1 / O2;
    }
    else if (Operator.equals("%")) {
      return O1 * (O2 / 100);
    } else {
      System.out.println("Operator Error");
    }
    return 0.0;
  }    //End Method answer()

  public static void main(String args[]) {
    JFrame f = new JFrame("Calculator Demo");
    f.setDefaultCloseOperation(f.EXIT_ON_CLOSE);
    f.setContentPane(new CalculatorDemo());
    f.setResizable(false);
    f.pack();
    f.setVisible(true);
  }    //End Method Main
}      //End Class "CalculatorDemo"