利用 Java 开发一个可以进行简单的四则运算的图形化计算器，要求计算器至少能够实现基本的加减乘除运算、开方和清空功能，其中C按钮用于实现清空操作，直接将显示置零。

好的，这是一个比较简单的任务，您需要以下几个步骤来完成这个任务：

1. 创建一个 Java GUI 窗口，在窗口中添加按钮和文本框等组件。
2. 为每个按钮添加监听器，当用户点击按钮时，执行相应的操作。
3. 实现四则运算和开方功能的算法，可以使用 Java 中的 Math 类库来实现。
4. 在文本框中显示计算结果。

以下是代码示例，仅供参考：

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

public class Calculator extends JFrame implements ActionListener {
    private JTextField textField;
    private JButton button0, button1, button2, button3, button4, button5, button6, button7, button8, button9;
    private JButton buttonAdd, buttonSubtract, buttonMultiply, buttonDivide, buttonSqrt, buttonClear, buttonEqual;
    private double num1, num2, result;
    private String operator;

    public Calculator() {
        // 设置窗口标题和大小
        super("Calculator");
        setSize(300, 300);

        // 创建文本框和按钮
        textField = new JTextField(20);
        button0 = new JButton("0");
        button1 = new JButton("1");
        button2 = new JButton("2");
        button3 = new JButton("3");
        button4 = new JButton("4");
        button5 = new JButton("5");
        button6 = new JButton("6");
        button7 = new JButton("7");
        button8 = new JButton("8");
        button9 = new JButton("9");
        buttonAdd = new JButton("+");
        buttonSubtract = new JButton("-");
        buttonMultiply = new JButton("*");
        buttonDivide = new JButton("/");
        buttonSqrt = new JButton("sqrt");
        buttonClear = new JButton("C");
        buttonEqual = new JButton("=");

        // 添加按钮监听器
        button0.addActionListener(this);
        button1.addActionListener(this);
        button2.addActionListener(this);
        button3.addActionListener(this);
        button4.addActionListener(this);
        button5.addActionListener(this);
        button6.addActionListener(this);
        button7.addActionListener(this);
        button8.addActionListener(this);
        button9.addActionListener(this);
        buttonAdd.addActionListener(this);
        buttonSubtract.addActionListener(this);
        buttonMultiply.addActionListener(this);
        buttonDivide.addActionListener(this);
        buttonSqrt.addActionListener(this);
        buttonClear.addActionListener(this);
        buttonEqual.addActionListener(this);

        // 添加组件到窗口
        JPanel panel1 = new JPanel(new GridLayout(4, 4));
        panel1.add(button7);
        panel1.add(button8);
        panel1.add(button9);
        panel1.add(buttonAdd);
        panel1.add(button4);
        panel1.add(button5);
        panel1.add(button6);
        panel1.add(buttonSubtract);
        panel1.add(button1);
        panel1.add(button2);
        panel1.add(button3);
        panel1.add(buttonMultiply);
        panel1.add(buttonSqrt);
        panel1.add(button0);
        panel1.add(buttonClear);
        panel1.add(buttonDivide);
        JPanel panel2 = new JPanel(new FlowLayout());
        panel2.add(textField);
        JPanel panel3 = new JPanel(new FlowLayout());
        panel3.add(buttonEqual);
        Container container = getContentPane();
        container.setLayout(new BorderLayout());
        container.add(panel2, BorderLayout.NORTH);
        container.add(panel1, BorderLayout.CENTER);
        container.add(panel3, BorderLayout.SOUTH);

        // 显示窗口
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == button0) {
            textField.setText(textField.getText() + "0");
        } else if (e.getSource() == button1) {
            textField.setText(textField.getText() + "1");
        } else if (e.getSource() == button2) {
            textField.setText(textField.getText() + "2");
        } else if (e.getSource() == button3) {
            textField.setText(textField.getText() + "3");
        } else if (e.getSource() == button4) {
            textField.setText(textField.getText() + "4");
        } else if (e.getSource() == button5) {
            textField.setText(textField.getText() + "5");
        } else if (e.getSource() == button6) {
            textField.setText(textField.getText() + "6");
        } else if (e.getSource() == button7) {
            textField.setText(textField.getText() + "7");
        } else if (e.getSource() == button8) {
            textField.setText(textField.getText() + "8");
        } else if (e.getSource() == button9) {
            textField.setText(textField.getText() + "9");
        } else if (e.getSource() == buttonAdd) {
            num1 = Double.parseDouble(textField.getText());
            operator = "+";
            textField.setText("");
        } else if (e.getSource() == buttonSubtract) {
            num1 = Double.parseDouble(textField.getText());
            operator = "-";
            textField.setText("");
        } else if (e.getSource() == buttonMultiply) {
            num1 = Double.parseDouble(textField.getText());
            operator = "*";
            textField.setText("");
        } else if (e.getSource() == buttonDivide) {
            num1 = Double.parseDouble(textField.getText());
            operator = "/";
            textField.setText("");
        } else if (e.getSource() == buttonSqrt) {
            num1 = Double.parseDouble(textField.getText());
            result = Math.sqrt(num1);
            textField.setText(Double.toString(result));
        } else if (e.getSource() == buttonClear) {
            textField.setText("");
        } else if (e.getSource() == buttonEqual) {
            num2 = Double.parseDouble(textField.getText());
            if (operator.equals("+")) {
                result = num1 + num2;
            } else if (operator.equals("-")) {
                result = num1 - num2;
            } else if (operator.equals("*")) {
                result = num1 * num2;
            } else if (operator.equals("/")) {
                result = num1 / num2;
            }
            textField.setText(Double.toString(result));
        }
    }

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

以上代码实现了一个简单的图形化计算器，支持四则运算和开方功能，使用了 Java 的 GUI 编程和事件监听。