请用Java图形界面的知识，编写一个计算器，要求实现基本的加减乘除运算

以下是一个简单的Java图形界面计算器，实现基本的加减乘除运算：

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

public class Calculator extends JFrame implements ActionListener {
    private JTextField inputField;
    private JButton addButton, subtractButton, multiplyButton, divideButton, equalsButton, clearButton;
    private double num1, num2, result;
    private String operator;

    public Calculator() {
        setTitle("Calculator");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(300, 200);

        // 创建文本框和按钮
        inputField = new JTextField(20);
        addButton = new JButton("+");
        subtractButton = new JButton("-");
        multiplyButton = new JButton("*");
        divideButton = new JButton("/");
        equalsButton = new JButton("=");
        clearButton = new JButton("C");

        // 设置按钮的事件监听器
        addButton.addActionListener(this);
        subtractButton.addActionListener(this);
        multiplyButton.addActionListener(this);
        divideButton.addActionListener(this);
        equalsButton.addActionListener(this);
        clearButton.addActionListener(this);

        // 创建面板并添加组件
        JPanel panel = new JPanel();
        panel.add(inputField);
        panel.add(addButton);
        panel.add(subtractButton);
        panel.add(multiplyButton);
        panel.add(divideButton);
        panel.add(equalsButton);
        panel.add(clearButton);

        // 将面板添加到窗口
        add(panel);

        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        // 获取按钮上的文本
        String buttonText = e.getActionCommand();

        // 根据按钮的文本进行相应的操作
        switch (buttonText) {
            case "+":
                operator = "+";
                num1 = Double.parseDouble(inputField.getText());
                inputField.setText("");
                break;
            case "-":
                operator = "-";
                num1 = Double.parseDouble(inputField.getText());
                inputField.setText("");
                break;
            case "*":
                operator = "*";
                num1 = Double.parseDouble(inputField.getText());
                inputField.setText("");
                break;
            case "/":
                operator = "/";
                num1 = Double.parseDouble(inputField.getText());
                inputField.setText("");
                break;
            case "=":
                num2 = Double.parseDouble(inputField.getText());
                switch (operator) {
                    case "+":
                        result = num1 + num2;
                        break;
                    case "-":
                        result = num1 - num2;
                        break;
                    case "*":
                        result = num1 * num2;
                        break;
                    case "/":
                        result = num1 / num2;
                        break;
                }
                inputField.setText(Double.toString(result));
                break;
            case "C":
                inputField.setText("");
                break;
        }
    }

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

运行程序，即可看到一个简单的计算器界面，可以进行基本的加减乘除运算。