java窗体简易计算器加减乘除

以下是一个简易的 Java 窗体计算器，支持加减乘除四则运算：

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

public class Calculator extends JFrame implements ActionListener {
    private JTextField tfNum1, tfNum2, tfResult;
    private JButton btnAdd, btnSub, btnMul, btnDiv;

    public Calculator() {
        super("Calculator");
        setSize(400, 200);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new GridLayout(4, 2));

        JLabel lblNum1 = new JLabel("Number 1:");
        tfNum1 = new JTextField(10);
        add(lblNum1);
        add(tfNum1);

        JLabel lblNum2 = new JLabel("Number 2:");
        tfNum2 = new JTextField(10);
        add(lblNum2);
        add(tfNum2);

        JLabel lblResult = new JLabel("Result:");
        tfResult = new JTextField(10);
        tfResult.setEditable(false);
        add(lblResult);
        add(tfResult);

        btnAdd = new JButton("Add");
        add(btnAdd);
        btnAdd.addActionListener(this);

        btnSub = new JButton("Subtract");
        add(btnSub);
        btnSub.addActionListener(this);

        btnMul = new JButton("Multiply");
        add(btnMul);
        btnMul.addActionListener(this);

        btnDiv = new JButton("Divide");
        add(btnDiv);
        btnDiv.addActionListener(this);

        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        double num1 = Double.parseDouble(tfNum1.getText());
        double num2 = Double.parseDouble(tfNum2.getText());
        double result = 0;

        if (e.getSource() == btnAdd) {
            result = num1 + num2;
        } else if (e.getSource() == btnSub) {
            result = num1 - num2;
        } else if (e.getSource() == btnMul) {
            result = num1 * num2;
        } else if (e.getSource() == btnDiv) {
            result = num1 / num2;
        }

        tfResult.setText(Double.toString(result));
    }

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

该计算器使用了 Java 的 Swing GUI 库来创建窗体界面，包含两个文本框用于输入数字，一个文本框用于显示结果，以及四个按钮用于进行四则运算。在点击按钮后，通过 `ActionListener` 接口中的 `actionPerformed` 方法来计算并显示结果。