java 简单计算器

以下是一个使用Java Swing编写的简易计算器程序，支持基本的加、减、乘、除四则运算：

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, buttonSub, buttonMul, buttonDiv, buttonDot, buttonEqual, buttonClear;
    private double num1 = 0, num2 = 0, result = 0;
    private String operator = "";

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

        textField = new JTextField(20);
        textField.setEditable(false);
        add(textField, BorderLayout.NORTH);

        JPanel panel = new JPanel(new GridLayout(4, 4));
        button7 = new JButton("7");
        button8 = new JButton("8");
        button9 = new JButton("9");
        buttonDiv = new JButton("/");
        button4 = new JButton("4");
        button5 = new JButton("5");
        button6 = new JButton("6");
        buttonMul = new JButton("*");
        button1 = new JButton("1");
        button2 = new JButton("2");
        button3 = new JButton("3");
        buttonSub = new JButton("-");
        button0 = new JButton("0");
        buttonDot = new JButton(".");
        buttonEqual = new JButton("=");
        buttonAdd = new JButton("+");
        buttonClear = new JButton("C");

        panel.add(button7);
        panel.add(button8);
        panel.add(button9);
        panel.add(buttonDiv);
        panel.add(button4);
        panel.add(button5);
        panel.add(button6);
        panel.add(buttonMul);
        panel.add(button1);
        panel.add(button2);
        panel.add(button3);
        panel.add(buttonSub);
        panel.add(button0);
        panel.add(buttonDot);
        panel.add(buttonEqual);
        panel.add(buttonAdd);
        panel.add(buttonClear);

        add(panel, 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);
        buttonAdd.addActionListener(this);
        buttonSub.addActionListener(this);
        buttonMul.addActionListener(this);
        buttonDiv.addActionListener(this);
        buttonDot.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() == buttonAdd) {
            num1 = Double.parseDouble(textField.getText());
            operator = "+";
            textField.setText("");
        } else if (e.getSource() == buttonSub) {
            num1 = Double.parseDouble(textField.getText());
            operator = "-";
            textField.setText("");
        } else if (e.getSource() == buttonMul) {
            num1 = Double.parseDouble(textField.getText());
            operator = "*";
            textField.setText("");
        } else if (e.getSource() == buttonDiv) {
            num1 = Double.parseDouble(textField.getText());
            operator = "/";
            textField.setText("");
        } else if (e.getSource() == buttonDot) {
            textField.setText(textField.getText() + ".");
        } 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("");
        }
    }

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