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

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);
            }
        });
    }
}

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

class CalculatorPanel extends JPanel {
    private static int sub = 0;
    private static int add = 0;

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

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

        operations = new JButton("Сложения/вычитания");
        operations.setEnabled(false);
        add(operations, BorderLayout.SOUTH);

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

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

        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);
    }

    private void addButton(String label, ActionListener listener) {
        JButton button = new JButton(label);
        button.addActionListener(listener);
        panel.add(button);
    }

    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);
        }
    }

    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;
            }
        }
    }

    public void calculate(double x) {
        if (lastCommand.equals("+")) {
            result += x;
            this.add +=1;
        } else if (lastCommand.equals("-")) {
            result -= x;
            this.sub += 1;
        } else if (lastCommand.equals("*")) {
            result *= x;
        }
        else if (lastCommand.equals("/")) {
            result /= x;
        }
        else if (lastCommand.equals("=")) {
            result = x;
        }
        display.setText("" + result);
        operations.setText(this.add + " / "  + this.sub);
    }

    private JButton display;
    private JButton operations;
    private JPanel panel;
    private double result;
    private String lastCommand;
    private boolean start;
}