用java的图形用户界面写简易计算器

可以使用Java Swing来编写一个简易计算器，下面是一个示例代码：

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 button0, button1, button2, button3, button4, button5, button6, button7, button8, button9;
    private JButton buttonPlus, buttonMinus, buttonMultiply, buttonDivide, buttonEquals, buttonClear;
    private double num1 = 0, num2 = 0, result = 0;
    private String operator = "";

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

        textField = new JTextField(20);
        textField.setEditable(false);

        JPanel panelTop = new JPanel();
        panelTop.add(textField);

        JPanel panelMiddle = new JPanel();
        panelMiddle.setLayout(new GridLayout(4, 4, 5, 5));
        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("*");
        buttonClear = new JButton("C");
        button0 = new JButton("0");
        buttonEquals = new JButton("=");
        buttonDivide = new JButton("/");
        panelMiddle.add(button7);
        panelMiddle.add(button8);
        panelMiddle.add(button9);
        panelMiddle.add(buttonPlus);
        panelMiddle.add(button4);
        panelMiddle.add(button5);
        panelMiddle.add(button6);
        panelMiddle.add(buttonMinus);
        panelMiddle.add(button1);
        panelMiddle.add(button2);
        panelMiddle.add(button3);
        panelMiddle.add(buttonMultiply);
        panelMiddle.add(buttonClear);
        panelMiddle.add(button0);
        panelMiddle.add(buttonEquals);
        panelMiddle.add(buttonDivide);

        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);
        buttonEquals.addActionListener(this);
        buttonClear.addActionListener(this);

        JPanel panelBottom = new JPanel();
        panelBottom.add(panelMiddle);

        Container container = getContentPane();
        container.setLayout(new BorderLayout());
        container.add(panelTop, BorderLayout.NORTH);
        container.add(panelBottom, BorderLayout.CENTER);

        setVisible(true);
    }

    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() == buttonClear) {
            textField.setText("");
            num1 = 0;
            num2 = 0;
            result = 0;
            operator = "";
        } 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() == buttonEquals) {
            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("" + result);
        }
    }

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

这个计算器支持加、减、乘、除四种基本运算，以及清空和等于两种操作。用户可以通过点击按钮输入数字和选择运算符，即可得到计算结果。