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

public class SimpleCalculator {
    private JFrame frame;
    private JTextField displayField;
    private String currentInput = "";
    private double result = 0;
    private char operator = ' ';

    public SimpleCalculator() {
        frame = new JFrame("Simple Calculator");
        frame.setLayout(new BorderLayout());

        displayField = new JTextField();
        displayField.setHorizontalAlignment(JTextField.RIGHT);
        displayField.setEditable(false);
        frame.add(displayField, BorderLayout.NORTH);

        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(4, 4));

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

        for (String label : buttonLabels) {
            JButton button = new JButton(label);
            button.addActionListener(new ButtonClickListener());
            buttonPanel.add(button);
        }

        frame.add(buttonPanel, BorderLayout.CENTER);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }

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

            if (command.matches("[0-9]")) {
                currentInput += command;
                displayField.setText(currentInput);
            } else if (command.equals("+") || command.equals("-") || command.equals("*") || command.equals("/") || command.equals("%")) {
                operator = command.charAt(0);
                result = Double.parseDouble(currentInput);
                currentInput = "";
            } else if (command.equals("=")) {
                try {
                    double secondOperand = Double.parseDouble(currentInput);
                    switch (operator) {
                        case '+':
                            result += secondOperand;
                            break;
                        case '-':
                            result -= secondOperand;
                            break;
                        case '*':
                            result *= secondOperand;
                            break;
                        case '/':
                            if (secondOperand == 0) {
                                throw new ArithmeticException("Divide by zero error");
                            }
                            result /= secondOperand;
                            break;
                        case '%':
                            result %= secondOperand;
                            break;
                    }
                    displayField.setText(String.valueOf(result));
                } catch (NumberFormatException ex) {
                    displayField.setText("Invalid input");
                } catch (ArithmeticException ex) {
                    displayField.setText("Divide by zero error");
                }
                currentInput = "";
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new SimpleCalculator());
    }
}