请用java实现一个计算器

以下是一个简单的 Java 计算器实现：

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, buttonSubtract, buttonMultiply, buttonDivide, buttonEqual, buttonClear;
    private double currentValue = 0;
    private String currentOperator = "";
    
    public Calculator() {
        super("Calculator");
        setLayout(new BorderLayout());
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        textField = new JTextField();
        textField.setHorizontalAlignment(JTextField.RIGHT);
        add(textField, BorderLayout.NORTH);
        
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(4, 4, 5, 5));
        
        button7 = new JButton("7");
        button7.addActionListener(this);
        buttonPanel.add(button7);
        
        button8 = new JButton("8");
        button8.addActionListener(this);
        buttonPanel.add(button8);
        
        button9 = new JButton("9");
        button9.addActionListener(this);
        buttonPanel.add(button9);
        
        buttonDivide = new JButton("/");
        buttonDivide.addActionListener(this);
        buttonPanel.add(buttonDivide);
        
        button4 = new JButton("4");
        button4.addActionListener(this);
        buttonPanel.add(button4);
        
        button5 = new JButton("5");
        button5.addActionListener(this);
        buttonPanel.add(button5);
        
        button6 = new JButton("6");
        button6.addActionListener(this);
        buttonPanel.add(button6);
        
        buttonMultiply = new JButton("*");
        buttonMultiply.addActionListener(this);
        buttonPanel.add(buttonMultiply);
        
        button1 = new JButton("1");
        button1.addActionListener(this);
        buttonPanel.add(button1);
        
        button2 = new JButton("2");
        button2.addActionListener(this);
        buttonPanel.add(button2);
        
        button3 = new JButton("3");
        button3.addActionListener(this);
        buttonPanel.add(button3);
        
        buttonSubtract = new JButton("-");
        buttonSubtract.addActionListener(this);
        buttonPanel.add(buttonSubtract);
        
        button0 = new JButton("0");
        button0.addActionListener(this);
        buttonPanel.add(button0);
        
        buttonClear = new JButton("C");
        buttonClear.addActionListener(this);
        buttonPanel.add(buttonClear);
        
        buttonEqual = new JButton("=");
        buttonEqual.addActionListener(this);
        buttonPanel.add(buttonEqual);
        
        buttonAdd = new JButton("+");
        buttonAdd.addActionListener(this);
        buttonPanel.add(buttonAdd);
        
        add(buttonPanel, BorderLayout.CENTER);
        
        pack();
        setLocationRelativeTo(null);
        setVisible(true);
    }
    
    public void actionPerformed(ActionEvent e) {
        String buttonText = e.getActionCommand();
        
        if (buttonText.equals("C")) {
            currentValue = 0;
            currentOperator = "";
            textField.setText("");
            return;
        }
        
        if (buttonText.equals("+") || buttonText.equals("-") || buttonText.equals("*") || buttonText.equals("/")) {
            currentValue = Double.parseDouble(textField.getText());
            currentOperator = buttonText;
            textField.setText("");
            return;
        }
        
        if (buttonText.equals("=")) {
            double newValue = Double.parseDouble(textField.getText());
            
            if (currentOperator.equals("+")) {
                currentValue += newValue;
            }
            else if (currentOperator.equals("-")) {
                currentValue -= newValue;
            }
            else if (currentOperator.equals("*")) {
                currentValue *= newValue;
            }
            else if (currentOperator.equals("/")) {
                currentValue /= newValue;
            }
            
            currentOperator = "";
            textField.setText(Double.toString(currentValue));
            return;
        }
        
        String currentText = textField.getText();
        textField.setText(currentText + buttonText);
    }
    
    public static void main(String[] args) {
        Calculator calculator = new Calculator();
    }
}

该计算器使用了 JFrame 类来创建一个窗口界面，并使用了 JTextField 和 JButton 等组件来实现用户界面。用户可以通过单击按钮来输入数字和操作符，并通过单击“C”按钮来清除计算器的状态。在用户单击“=”按钮时，计算器将执行相应的数学运算，并将结果显示在文本框中。