java设计并实现一个类似于windows操作系统附件中自带的计算器的一款简单的计算器，要求界面美观，设计合理；带有常用的菜单并实现其功能；能完成加、减、乘、除等简单的计算，在下面写出其核心代码。

好的，我收到了你的要求，并理解了你的问题。下面是一个简单的 Java 计算器的核心代码，希望能够解决你的问题：

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

public class SimpleCalculator extends JFrame implements ActionListener {
    private JTextField result;
    private double operand1, operand2;
    private String operator;

    public SimpleCalculator() {
        setTitle("简单计算器");
        setSize(260, 240);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        JMenuBar menubar = new JMenuBar();
        setJMenuBar(menubar);
        JMenu file = new JMenu("文件");
        menubar.add(file);
        JMenuItem itemExit = new JMenuItem("退出");
        file.add(itemExit);
        itemExit.addActionListener(this);

        JMenu edit = new JMenu("编辑");
        menubar.add(edit);
        JMenuItem itemCopy = new JMenuItem("复制");
        JMenuItem itemPaste = new JMenuItem("粘贴");
        edit.add(itemCopy);
        edit.add(itemPaste);
        itemCopy.addActionListener(this);
        itemPaste.addActionListener(this);

        result = new JTextField();
        result.setEditable(false);
        add(result, BorderLayout.NORTH);

        JPanel panel = new JPanel(new GridLayout(4, 4));
        add(panel, BorderLayout.CENTER);
        addButton(panel, "7");
        addButton(panel, "8");
        addButton(panel, "9");
        addButton(panel, "/");
        addButton(panel, "4");
        addButton(panel, "5");
        addButton(panel, "6");
        addButton(panel, "*");
        addButton(panel, "1");
        addButton(panel, "2");
        addButton(panel, "3");
        addButton(panel, "-");
        addButton(panel, "0");
        addButton(panel, ".");
        addButton(panel, "=");
        addButton(panel, "+");
    }

    private void addButton(Container container, String text) {
        JButton button = new JButton(text);
        button.addActionListener(this);
        container.add(button);
    }

    public void actionPerformed(ActionEvent event) {
        String action = event.getActionCommand();
        if (action.equals("退出")) {
            System.exit(0);
        } else if (action.equals("复制")) {
            result.copy();
        } else if (action.equals("粘贴")) {
            result.paste();
        } else if (action.matches("[0-9]")) {
            result.setText(result.getText() + action);
        } else if (action.equals(".")) {
            if (!result.getText().contains(".")) {
                result.setText(result.getText() + ".");
            }
        } else if (action.equals("+")) {
            operand1 = Double.parseDouble(result.getText());
            operator = "+";
            result.setText("");
        } else if (action.equals("-")) {
            operand1 = Double.parseDouble(result.getText());
            operator = "-";
            result.setText("");
        } else if (action.equals("*")) {
            operand1 = Double.parseDouble(result.getText());
            operator = "*";
            result.setText("");
        } else if (action.equals("/")) {
            operand1 = Double.parseDouble(result.getText());
            operator = "/";
            result.setText("");
        } else if (action.equals("=")) {
            operand2 = Double.parseDouble(result.getText());
            if (operator.equals("+")) {
                result.setText(Double.toString(operand1 + operand2));
            } else if (operator.equals("-")) {
                result.setText(Double.toString(operand1 - operand2));
            } else if (operator.equals("*")) {
                result.setText(Double.toString(operand1 * operand2));
            } else {
                result.setText(Double.toString(operand1 / operand2));
            }
        }
    }

    public static void main(String[] args) {
        SimpleCalculator calculator = new SimpleCalculator();
        calculator.setVisible(true);
    }
}

这段代码实现了一个类似于 Windows 操作系统中自带的计算器的简单计算器。它有一个美观的界面，带有常用的菜单并且能够完成加、减、乘、除等简单的计算。

如果你还有其他问题或有需要进一步解释的地方，请随时告诉我，谢谢！