基于swing的计算器带注释

以下是一个基于Swing的计算器，其中包含注释：

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

public class Calculator extends JFrame implements ActionListener {

    private JTextField display;
    private JButton[] buttons;
    private String[] buttonLabels = {"7", "8", "9", "/", "4", "5", "6", "*", "1", "2", "3", "-", "0", ".", "=", "+"};
    private double result = 0;
    private String operator = "";
    private boolean start = true;

    public Calculator() {
        setTitle("Calculator");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(400, 400);
        setLayout(new BorderLayout());

        display = new JTextField();
        display.setEditable(false);
        add(display, BorderLayout.NORTH);

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

        buttons = new JButton[buttonLabels.length];
        for (int i = 0; i < buttonLabels.length; i++) {
            buttons[i] = new JButton(buttonLabels[i]);
            buttons[i].addActionListener(this);
            buttonPanel.add(buttons[i]);
        }

        add(buttonPanel, BorderLayout.CENTER);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        String input = e.getActionCommand();

        if (start) {
            if (input.equals("-")) {
                display.setText(input);
                start = false;
            } else {
                operator = input;
                start = false;
            }
        } else {
            double inputValue = Double.parseDouble(display.getText());
            if (operator.equals("+")) {
                result += inputValue;
            } else if (operator.equals("-")) {
                result -= inputValue;
            } else if (operator.equals("*")) {
                result *= inputValue;
            } else if (operator.equals("/")) {
                result /= inputValue;
            } else if (operator.equals("=")) {
                result = inputValue;
            }
            display.setText("" + result);
            operator = input;
        }
    }

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

这个计算器使用了Swing框架来创建用户界面，并实现了基本的加减乘除运算。其中，`actionPerformed`方法用于处理按钮点击事件，`start`变量用于标记是否开始一个新的计算，`result`变量用于保存计算结果，`operator`变量用于保存当前的操作符。