​编写Java GUI程序，实现一个简单计算器。要求如下： ‍ ​（1）设计的界面如下图所示：窗体的标题栏显示“模拟计算器—江海大”，1个文本框用于显示输入字符和计算结果；20个按钮控件作为字符输入按键或者功能按键。程序的外观对64开平方根的运行结果 ‍ ​（2）计算功能：实现加、减、乘、除等双目运算，开平方、百分数等单目运算； ‍ ​（3）辅助功能：按钮“C”清空文本框；按钮“←”退格，删除文本框中最右边的一个字符。 ‍ ‍ ​

以下是一个简单的 Java GUI 程序，实现了一个简易计算器的功能，包括加、减、乘、除、开平方、百分数、清空和退格功能。

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 textField;

    private JButton btn1, btn2, btn3, btn4, btn5, btn6, btn7, btn8, btn9, btn0;
    private JButton btnAdd, btnSub, btnMul, btnDiv, btnSqrt, btnPercent, btnClear, btnDelete, btnEqual;

    private double num1 = 0, num2 = 0, result = 0;
    private String operator = "";

    public Calculator() {
        // 设置窗体的标题和大小
        setTitle("模拟计算器-江海大");
        setSize(350, 400);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // 创建一个面板，用于放置文本框和按钮
        JPanel panel = new JPanel();
        panel.setLayout(null);

        // 创建文本框
        textField = new JTextField();
        textField.setBounds(10, 10, 320, 50);
        textField.setFont(new Font("Arial", Font.PLAIN, 24));
        textField.setEditable(false);
        panel.add(textField);

        // 创建数字按钮
        btn1 = new JButton("1");
        btn1.setBounds(10, 80, 60, 60);
        btn1.setFont(new Font("Arial", Font.PLAIN, 24));
        btn1.addActionListener(this);
        panel.add(btn1);

        btn2 = new JButton("2");
        btn2.setBounds(80, 80, 60, 60);
        btn2.setFont(new Font("Arial", Font.PLAIN, 24));
        btn2.addActionListener(this);
        panel.add(btn2);

        btn3 = new JButton("3");
        btn3.setBounds(150, 80, 60, 60);
        btn3.setFont(new Font("Arial", Font.PLAIN, 24));
        btn3.addActionListener(this);
        panel.add(btn3);

        btn4 = new JButton("4");
        btn4.setBounds(10, 150, 60, 60);
        btn4.setFont(new Font("Arial", Font.PLAIN, 24));
        btn4.addActionListener(this);
        panel.add(btn4);

        btn5 = new JButton("5");
        btn5.setBounds(80, 150, 60, 60);
        btn5.setFont(new Font("Arial", Font.PLAIN, 24));
        btn5.addActionListener(this);
        panel.add(btn5);

        btn6 = new JButton("6");
        btn6.setBounds(150, 150, 60, 60);
        btn6.setFont(new Font("Arial", Font.PLAIN, 24));
        btn6.addActionListener(this);
        panel.add(btn6);

        btn7 = new JButton("7");
        btn7.setBounds(10, 220, 60, 60);
        btn7.setFont(new Font("Arial", Font.PLAIN, 24));
        btn7.addActionListener(this);
        panel.add(btn7);

        btn8 = new JButton("8");
        btn8.setBounds(80, 220, 60, 60);
        btn8.setFont(new Font("Arial", Font.PLAIN, 24));
        btn8.addActionListener(this);
        panel.add(btn8);

        btn9 = new JButton("9");
        btn9.setBounds(150, 220, 60, 60);
        btn9.setFont(new Font("Arial", Font.PLAIN, 24));
        btn9.addActionListener(this);
        panel.add(btn9);

        btn0 = new JButton("0");
        btn0.setBounds(80, 290, 60, 60);
        btn0.setFont(new Font("Arial", Font.PLAIN, 24));
        btn0.addActionListener(this);
        panel.add(btn0);

        // 创建运算符按钮
        btnAdd = new JButton("+");
        btnAdd.setBounds(220, 80, 60, 60);
        btnAdd.setFont(new Font("Arial", Font.PLAIN, 24));
        btnAdd.addActionListener(this);
        panel.add(btnAdd);

        btnSub = new JButton("-");
        btnSub.setBounds(290, 80, 60, 60);
        btnSub.setFont(new Font("Arial", Font.PLAIN, 24));
        btnSub.addActionListener(this);
        panel.add(btnSub);

        btnMul = new JButton("×");
        btnMul.setBounds(220, 150, 60, 60);
        btnMul.setFont(new Font("Arial", Font.PLAIN, 24));
        btnMul.addActionListener(this);
        panel.add(btnMul);

        btnDiv = new JButton("÷");
        btnDiv.setBounds(290, 150, 60, 60);
        btnDiv.setFont(new Font("Arial", Font.PLAIN, 24));
        btnDiv.addActionListener(this);
        panel.add(btnDiv);

        btnSqrt = new JButton("√");
        btnSqrt.setBounds(220, 220, 60, 60);
        btnSqrt.setFont(new Font("Arial", Font.PLAIN, 24));
        btnSqrt.addActionListener(this);
        panel.add(btnSqrt);

        btnPercent = new JButton("%");
        btnPercent.setBounds(290, 220, 60, 60);
        btnPercent.setFont(new Font("Arial", Font.PLAIN, 24));
        btnPercent.addActionListener(this);
        panel.add(btnPercent);

        btnClear = new JButton("C");
        btnClear.setBounds(220, 290, 60, 60);
        btnClear.setFont(new Font("Arial", Font.PLAIN, 24));
        btnClear.addActionListener(this);
        panel.add(btnClear);

        btnDelete = new JButton("←");
        btnDelete.setBounds(290, 290, 60, 60);
        btnDelete.setFont(new Font("Arial", Font.PLAIN, 24));
        btnDelete.addActionListener(this);
        panel.add(btnDelete);

        btnEqual = new JButton("=");
        btnEqual.setBounds(220, 10, 130, 50);
        btnEqual.setFont(new Font("Arial", Font.PLAIN, 24));
        btnEqual.addActionListener(this);
        panel.add(btnEqual);

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

        // 显示窗体
        setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();
        switch (command) {
            case "0":
            case "1":
            case "2":
            case "3":
            case "4":
            case "5":
            case "6":
            case "7":
            case "8":
            case "9":
                // 数字按键
                textField.setText(textField.getText() + command);
                break;
            case "+":
            case "-":
            case "×":
            case "÷":
                // 双目运算符按键
                num1 = Double.parseDouble(textField.getText());
                operator = command;
                textField.setText("");
                break;
            case "√":
            case "%":
                // 单目运算符按键
                num1 = Double.parseDouble(textField.getText());
                operator = command;
                calculate();
                break;
            case "C":
                // 清空按键
                num1 = 0;
                num2 = 0;
                operator = "";
                result = 0;
                textField.setText("");
                break;
            case "←":
                // 退格按键
                String text = textField.getText();
                if (text.length() > 0) {
                    textField.setText(text.substring(0, text.length() - 1));
                }
                break;
            case "=":
                // 等号按键
                num2 = Double.parseDouble(textField.getText());
                calculate();
                break;
        }
    }

    private void calculate() {
        switch (operator) {
            case "+":
                result = num1 + num2;
                break;
            case "-":
                result = num1 - num2;
                break;
            case "×":
                result = num1 * num2;
                break;
            case "÷":
                result = num1 / num2;
                break;
            case "√":
                result = Math.sqrt(num1);
                break;
            case "%":
                result = num1 / 100;
                break;
        }
        textField.setText(String.valueOf(result));
    }

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

运行程序后，可以看到一个简易计算器的界面，如下图所示：


可以通过点击不同的按钮，输入数字和运算符，进行计算。