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

public class Counter2158 extends JFrame implements ActionListener {
    private double result;
    private JTextField resultField;

    public Counter2158() {
        super("Simple Calculator");
        initializeCalculator();
    }

    private void initializeCalculator() {
        this.result = 0;

        // 创建布局
        setLayout(new BorderLayout());

        // 创建结果显示区域
        resultField = new JTextField("0", 10);
        resultField.setEditable(false);
        add(resultField, BorderLayout.NORTH);

        // 创建按钮面板
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(4, 4));

        // 添加按钮
        String[] buttons = {"+", "-", "*", "/", "Reset", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"};
        for (String buttonText : buttons) {
            JButton button = new JButton(buttonText);
            button.addActionListener(this);
            buttonPanel.add(button);
        }

        add(buttonPanel, BorderLayout.CENTER);

        // 设置窗口属性
        setSize(300, 200);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        setVisible(true); // 显示窗口
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();

        switch (command) {
            case "+":
                add(Double.parseDouble(resultField.getText()));
                break;
            case "-":
                subtract(Double.parseDouble(resultField.getText()));
                break;
            case "*":
                multiply(Double.parseDouble(resultField.getText()));
                break;
            case "/":
                try {
                    divide(Double.parseDouble(resultField.getText()));
                } catch (IllegalArgumentException ex) {
                    JOptionPane.showMessageDialog(this, ex.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
                    reset();
                }
                break;
            case "Reset":
                reset();
                break;
            default:
                add(Double.parseDouble(command));
                break;
        }

        resultField.setText(String.valueOf(result));
    }

    public void add(double num) {
        result += num;
    }

    public void subtract(double num) {
        result -= num;
    }

    public void multiply(double num) {
        result *= num;
    }

    public void divide(double num) {
        if (num == 0) {
            throw new IllegalArgumentException("Divisor cannot be zero.");
        }
        result /= num;
    }

    public void reset() {
        result = 0;
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(Counter2158::new);
    }
}