java计算器加减乘除

以下是一个使用Java Swing组件编写的简易计算器，可以进行加减乘除运算：

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

public class Calculator extends JFrame implements ActionListener {
    private static final long serialVersionUID = 1L;
    private JTextField num1, num2, result;
    private JButton add, subtract, multiply, divide;

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

        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(4, 2));

        num1 = new JTextField();
        num2 = new JTextField();
        result = new JTextField();
        result.setEditable(false);

        add = new JButton("+");
        subtract = new JButton("-");
        multiply = new JButton("*");
        divide = new JButton("/");

        add.addActionListener(this);
        subtract.addActionListener(this);
        multiply.addActionListener(this);
        divide.addActionListener(this);

        panel.add(new JLabel("Number 1:"));
        panel.add(num1);
        panel.add(new JLabel("Number 2:"));
        panel.add(num2);
        panel.add(new JLabel("Result:"));
        panel.add(result);
        panel.add(add);
        panel.add(subtract);
        panel.add(multiply);
        panel.add(divide);

        add(panel);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        double n1 = Double.parseDouble(num1.getText());
        double n2 = Double.parseDouble(num2.getText());        double r = 0;

        if (e.getSource() == add) {
            r = n1 + n2;
        } else if (e.getSource() == subtract) {
            r = n1 - n2;
        } else if (e.getSource() == multiply) {
            r = n1 * n2;
        } else if (e.getSource() == divide) {
            r = n1 / n2;
        }

        result.setText(String.valueOf(r));
    }

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