SimpleCalculator.java

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

public class SimpleCalculator {
    private JFrame frame;
    private JTextField textField;
    private double num1, num2, result;
    private char operator;

    public SimpleCalculator() {
        frame = new JFrame("Calculator");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 400);
        frame.setLayout(new BorderLayout());

        textField = new JTextField();
        textField.setFont(new Font("Arial", Font.BOLD, 18));
        textField.setHorizontalAlignment(JTextField.RIGHT);
        frame.add(textField, BorderLayout.NORTH);

        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(4, 4));
        frame.add(panel, BorderLayout.CENTER);

        String[] buttons = {
                "7", "8", "9", "/",
                "4", "5", "6", "*",
                "1", "2", "3", "-",
                "0", "C", "=", "+"
        };

        for (String text : buttons) {
            JButton button = new JButton(text);
            button.setFont(new Font("Arial", Font.BOLD, 18));
            panel.add(button);
            button.addActionListener(new ButtonClickListener());
        }

        frame.setVisible(true);
    }

    private class ButtonClickListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            String command = e.getActionCommand();

            if (command.charAt(0) >= '0' && command.charAt(0) <= '9') {
                textField.setText(textField.getText() + command);
            } else if (command.equals("C")) {
                textField.setText("");
            } else if (command.equals("=")) {
                num2 = Double.parseDouble(textField.getText());
                switch (operator) {
                    case '+': result = num1 + num2; break;
                    case '-': result = num1 - num2; break;
                    case '*': result = num1 * num2; break;
                    case '/': result = num1 / num2; break;
                }
                textField.setText(String.valueOf(result));
            } else {
                num1 = Double.parseDouble(textField.getText());
                operator = command.charAt(0);
                textField.setText("");
            }
        }
    }

    public static void main(String[] args) {
        new SimpleCalculator();
    }
}