用java写编写一个模拟计算器的程序，使用面板和网格布局，添加一个文本框，10个数字按钮(0-9)，4个加减乘除按钮，一个等号按钮，要求将计算公式和结果显示在文本框中。

以下是一个简单的Java GUI计算器程序，使用面板和网格布局。它包含一个文本框、10个数字按钮、4个运算符按钮和一个等号按钮。点击按钮后，计算公式和结果将显示在文本框中。

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

public class Calculator extends JFrame implements ActionListener {

    private static final long serialVersionUID = 1L;
    private JTextField textField;
    private JButton[] numberButtons = new JButton[10];
    private JButton[] operatorButtons = new JButton[4];
    private JButton addButton, subButton, mulButton, divButton;
    private JButton equalButton, clearButton;
    private JPanel panel;

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

    public Calculator() {
        setTitle("Calculator");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(300, 300);
        setResizable(false);

        textField = new JTextField();
        textField.setEditable(false);
        textField.setHorizontalAlignment(JTextField.RIGHT);

        addButton = new JButton("+");
        subButton = new JButton("-");
        mulButton = new JButton("*");
        divButton = new JButton("/");
        equalButton = new JButton("=");
        clearButton = new JButton("C");

        operatorButtons[0] = addButton;
        operatorButtons[1] = subButton;
        operatorButtons[2] = mulButton;
        operatorButtons[3] = divButton;

        for (int i = 0; i < 10; i++) {
            numberButtons[i] = new JButton(String.valueOf(i));
        }

        panel = new JPanel(new GridLayout(5, 4));
        panel.add(textField);

        for (int i = 1; i <= 9; i++) {
            if (i == 1) {
                panel.add(numberButtons[7]);
            } else if (i == 2) {
                panel.add(numberButtons[8]);
            } else if (i == 3) {
                panel.add(numberButtons[9]);
            } else if (i == 4) {
                panel.add(operatorButtons[0]);
            } else if (i == 5) {
                panel.add(numberButtons[4]);
            } else if (i == 6) {
                panel.add(numberButtons[5]);
            } else if (i == 7) {
                panel.add(numberButtons[6]);
            } else if (i == 8) {
                panel.add(operatorButtons[1]);
            } else if (i == 9) {
                panel.add(numberButtons[1]);
            } else {
                panel.add(numberButtons[0]);
            }
        }

        panel.add(operatorButtons[2]);
        panel.add(numberButtons[2]);
        panel.add(numberButtons[3]);
        panel.add(operatorButtons[3]);

        panel.add(numberButtons[0]);
        panel.add(clearButton);
        panel.add(equalButton);

        for (int i = 0; i < 10; i++) {
            numberButtons[i].addActionListener(this);
        }

        for (int i = 0; i < 4; i++) {
            operatorButtons[i].addActionListener(this);
        }

        equalButton.addActionListener(this);
        clearButton.addActionListener(this);

        add(panel);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        for (int i = 0; i < 10; i++) {
            if (e.getSource() == numberButtons[i]) {
                textField.setText(textField.getText().concat(String.valueOf(i)));
            }
        }

        if (e.getSource() == addButton) {
            num1 = Double.parseDouble(textField.getText());
            operator = '+';
            textField.setText("");
        }

        if (e.getSource() == subButton) {
            num1 = Double.parseDouble(textField.getText());
            operator = '-';
            textField.setText("");
        }

        if (e.getSource() == mulButton) {
            num1 = Double.parseDouble(textField.getText());
            operator = '*';
            textField.setText("");
        }

        if (e.getSource() == divButton) {
            num1 = Double.parseDouble(textField.getText());
            operator = '/';
            textField.setText("");
        }

        if (e.getSource() == equalButton) {
            num2 = Double.parseDouble(textField.getText());

            switch (operator) {
                case '+':
                    result = num1 + num2;
                    break;
                case '-':
                    result = num1 - num2;
                    break;
                case '*':
                    result = num1 * num2;
                    break;
                case '/':
                    result = num1 / num2;
                    break;
            }

            textField.setText(String.valueOf(result));
            num1 = result;
        }

        if (e.getSource() == clearButton) {
            textField.setText("");
        }
    }

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