用Java写一个带有页面的计算器用到的函数

以下是一个用 Java 编写的简单计算器页面，包含加、减、乘、除四则运算的函数：

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

public class Calculator extends JFrame implements ActionListener {
    private JButton button0, button1, button2, button3, button4, button5,
            button6, button7, button8, button9, buttonPlus, buttonMinus,
            buttonMultiply, buttonDivide, buttonEqual, buttonClear;
    private JTextField textField;
    private double num1 = 0, num2 = 0, result = 0;
    private String operator = "";

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

        JPanel panel1 = new JPanel(new GridLayout(1, 1));
        textField = new JTextField(20);
        textField.setHorizontalAlignment(JTextField.RIGHT);
        textField.setEditable(false);
        panel1.add(textField);
        add(panel1, BorderLayout.NORTH);

        JPanel panel2 = new JPanel(new GridLayout(4, 4));
        button7 = new JButton("7");
        button8 = new JButton("8");
        button9 = new JButton("9");
        buttonPlus = new JButton("+");
        button4 = new JButton("4");
        button5 = new JButton("5");
        button6 = new JButton("6");
        buttonMinus = new JButton("-");
        button1 = new JButton("1");
        button2 = new JButton("2");
        button3 = new JButton("3");
        buttonMultiply = new JButton("*");
        button0 = new JButton("0");
        buttonEqual = new JButton("=");
        buttonClear = new JButton("C");
        buttonDivide = new JButton("/");
        panel2.add(button7);
        panel2.add(button8);
        panel2.add(button9);
        panel2.add(buttonPlus);
        panel2.add(button4);
        panel2.add(button5);
        panel2.add(button6);
        panel2.add(buttonMinus);
        panel2.add(button1);
        panel2.add(button2);
        panel2.add(button3);
        panel2.add(buttonMultiply);
        panel2.add(button0);
        panel2.add(buttonEqual);
        panel2.add(buttonClear);
        panel2.add(buttonDivide);
        add(panel2, BorderLayout.CENTER);

        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);
        buttonPlus.addActionListener(this);
        buttonMinus.addActionListener(this);
        buttonMultiply.addActionListener(this);
        buttonDivide.addActionListener(this);
        buttonEqual.addActionListener(this);
        buttonClear.addActionListener(this);
    }

    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() == buttonPlus) {
            num1 = Double.parseDouble(textField.getText());
            operator = "+";
            textField.setText("");
        } else if (e.getSource() == buttonMinus) {
            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() == 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));
        } else if (e.getSource() == buttonClear) {
            textField.setText("");
            num1 = 0;
            num2 = 0;
            result = 0;
            operator = "";
        }
    }

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

这个计算器页面使用了 Java 的 Swing 库实现，包含 0 到 9 的数字按钮、加、减、乘、除四则运算按钮、等于按钮、清除按钮和文本框。当用户点击数字按钮时，该数字会显示在文本框中；当用户点击四则运算按钮时，程序会记录下第一个数字和运算符，并清空文本框；当用户点击等于按钮时，程序会计算出结果并显示在文本框中；当用户点击清除按钮时，程序会清空文本框和记录的数字和运算符。