lesson2/Calculator.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.script.ScriptEngineManager;
import javax.script.ScriptEngine;
import javax.script.ScriptException;

public class Calculator extends JFrame implements ActionListener {
    private JTextField display;
    private StringBuilder input;

    public Calculator() {
        input = new StringBuilder();
        display = new JTextField();
        display.setEditable(false);
        display.setFont(new Font("Arial", Font.BOLD, 32));
        display.setHorizontalAlignment(JTextField.RIGHT);
        display.setBackground(Color.LIGHT_GRAY);
        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(4, 4, 10, 10));
        panel.setBackground(Color.GRAY);

        String[] buttons = {
                "7", "8", "9", "/",
                "4", "5", "6", "*",
                "1", "2", "3", "-",
                "C", "0", "=", "+"
        };
        for (String text : buttons) {
            JButton button = new JButton(text);
            button.setFont(new Font("Arial", Font.PLAIN, 24));
            button.addActionListener(this);
            button.setBackground(Color.WHITE);
            panel.add(button);
        }
        add(display, BorderLayout.NORTH);
        add(panel, BorderLayout.CENTER);

        setTitle("Calculator");
        setSize(400, 500);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
    }
    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();

        if (command.charAt(0) == 'C') {
            input.setLength(0);
            display.setText("");
        } else if (command.charAt(0) == '=') {
            try {
                double result = evaluate(input.toString());
                display.setText(String.valueOf(result));
                input.setLength(0);
            } catch (ScriptException ex) {
                display.setText("Error");
                input.setLength(0);
            }
        } else {
            input.append(command);
            display.setText(input.toString());
        }
    }

    private double evaluate(String expression) throws ScriptException {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("JavaScript");
        return ((Number) engine.eval(expression)).doubleValue();
    }
//11122222
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            Calculator calculator = new Calculator();
            calculator.setVisible(true);
        });
    }
}