用JAVA编写一个计算器，能实现加减乘除、开平方、求阶乘等计算功能，计算器有图形化界面

好的，我会尽力满足您的需求。为了实现您的要求，我们可以使用 Java Swing 进行图形化界面开发，下面是一个简单的 Java 计算器实现：

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

public class Calculator extends JFrame implements ActionListener {
    private JPanel panel;
    private JTextField textField;
    private JButton addButton, subtractButton, multiplyButton, divideButton, sqrtButton, factorialButton, equalButton, clearButton;

    private double num1 = 0;
    private double num2 = 0;
    private char operator;

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

        panel = new JPanel(new GridLayout(4, 4));
        textField = new JTextField();
        addButton = new JButton("+");
        subtractButton = new JButton("-");
        multiplyButton = new JButton("*");
        divideButton = new JButton("/");
        sqrtButton = new JButton("sqrt");
        factorialButton = new JButton("!");
        equalButton = new JButton("=");
        clearButton = new JButton("C");

        addButton.addActionListener(this);
        subtractButton.addActionListener(this);
        multiplyButton.addActionListener(this);
        divideButton.addActionListener(this);
        sqrtButton.addActionListener(this);
        factorialButton.addActionListener(this);
        equalButton.addActionListener(this);
        clearButton.addActionListener(this);

        panel.add(addButton);
        panel.add(subtractButton);
        panel.add(multiplyButton);
        panel.add(divideButton);
        panel.add(sqrtButton);
        panel.add(factorialButton);
        panel.add(equalButton);
        panel.add(clearButton);
        panel.add(textField);
        add(panel);

        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == addButton) {
            operator = '+';
            num1 = Double.parseDouble(textField.getText());
            textField.setText("");
        } else if (e.getSource() == subtractButton) {
            operator = '-';
            num1 = Double.parseDouble(textField.getText());
            textField.setText("");
        } else if (e.getSource() == multiplyButton) {
            operator = '*';
            num1 = Double.parseDouble(textField.getText());
            textField.setText("");
        } else if (e.getSource() == divideButton) {
            operator = '/';
            num1 = Double.parseDouble(textField.getText());
            textField.setText("");
        } else if (e.getSource() == sqrtButton) {
            num1 = Double.parseDouble(textField.getText());
            num1 = Math.sqrt(num1);
            textField.setText(String.valueOf(num1));
        } else if (e.getSource() == factorialButton) {
            num1 = Double.parseDouble(textField.getText());
            num2 = 1;
            for (int i = 1; i <= num1; i++) {
                num2 = num2 * i;
            }
            textField.setText(String.valueOf(num2));
        } else if (e.getSource() == equalButton) {
            num2 = Double.parseDouble(textField.getText());
            switch (operator) {
                case '+':
                    num1 = num1 + num2;
                    break;
                case '-':
                    num1 = num1 - num2;
                    break;
                case '*':
                    num1 = num1 * num2;
                    break;
                case '/':
                    num1 = num1 / num2;
                    break;
            }
            textField.setText(String.valueOf(num1));
        } else if (e.getSource() == clearButton) {
            num1 = 0;
            num2 = 0;
            operator = ' ';
            textField.setText("");
        }
    }

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

这个程序能够实现加减乘除、开平方、求阶乘等计算功能，并且具有图形化界面。您可以将代码复制到您的 Java IDE 中进行编译和运行，或者将代码保存为 `Calculator.java` 文件，然后在命令行中使用 `javac Calculator.java` 命令进行编译，在使用 `java Calculator` 命令运行程序。