Java 電卓

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

public class Calculator extends JFrame implements ActionListener {
    private JTextField display;
    private JPanel panel;
    private StringBuilder currentInput;
    private double result;
    private String operator;

    public Calculator() {
        // Frame settings
        setTitle("Calculator");
        setSize(400, 600);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // Display settings
        display = new JTextField();
        display.setEditable(false);
        display.setFont(new Font("Arial", Font.BOLD, 24));
        add(display, BorderLayout.NORTH);

        // Button panel settings
        panel = new JPanel();
        panel.setLayout(new GridLayout(4, 4));

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

        for (String text : buttons) {
            JButton button = new JButton(text);
            button.setFont(new Font("Arial", Font.BOLD, 24));
            button.addActionListener(this);
            panel.add(button);
        }

        add(panel, BorderLayout.CENTER);

        currentInput = new StringBuilder();
        result = 0;
        operator = "";
    }

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

        if ("0123456789.".contains(command)) {
            currentInput.append(command);
            display.setText(currentInput.toString());
        } else if (command.equals("=")) {
            calculate();
            display.setText(String.valueOf(result));
            currentInput.setLength(0);
        } else {
            if (currentInput.length() > 0) {
                calculate();
                operator = command;
                display.setText(String.valueOf(result));
                currentInput.setLength(0);
            }
        }
    }

    private void calculate() {
        double input = currentInput.length() > 0 ? Double.parseDouble(currentInput.toString()) : 0;

        switch (operator) {
            case "+":
                result += input;
                break;
            case "-":
                result -= input;
                break;
            case "*":
                result *= input;
                break;
            case "/":
                result /= input;
                break;
            default:
                result = input;
                break;
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            Calculator calculator = new Calculator();
            calculator.setVisible(true);
        });
    }
}

1. javac Calculator.java
2. java Calculator