用java swing写一个四则运算计算器，在JLabel中选择加减乘除

好的，下面是一个简单的Java Swing四则运算计算器的示例代码。代码中使用了GridLayout布局管理器来布置按钮和文本框，setEditable()方法设置JTextField不可编辑，addActionListener()方法添加按钮点击事件监听器，try-catch语句用来捕获异常并在计算出错时显示错误信息。

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

public class Calculator extends JFrame implements ActionListener {
    private JPanel panel;
    private JTextField textField;
    private JLabel label;
    private JButton[] buttons;
    private String[] buttonLabels = {"7", "8", "9", "/", "4", "5", "6", "*", "1", "2", "3", "-", "0", ".", "=", "+"};

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

        panel = new JPanel();
        panel.setLayout(new GridLayout(4, 4));

        textField = new JTextField(10);
        textField.setEditable(false);
        label = new JLabel(" ");

        buttons = new JButton[16];
        for (int i = 0; i < 16; i++) {
            buttons[i] = new JButton(buttonLabels[i]);
            buttons[i].addActionListener(this);
            panel.add(buttons[i]);
        }

        add(textField, BorderLayout.NORTH);
        add(panel, BorderLayout.CENTER);
        add(label, BorderLayout.SOUTH);
    }

    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();
        if (command.equals("=")) {
            try {
                double result = evaluate(textField.getText());
                if (((JCheckBox)buttons[14]).isSelected()) {
                    result = Math.round(result);
                }
                textField.setText(Double.toString(result));
            } catch (Exception ex) {
                textField.setText("");
                label.setText("Error: " + ex.getMessage());
            }
        } else if (command.equals("C")) {
            textField.setText("");
            label.setText(" ");
        } else {
            textField.setText(textField.getText() + command);
        }
    }

    private double evaluate(String expression) {
        if (!isValidExpression(expression)) {
            throw new IllegalArgumentException("Invalid Expression");
        }
        String[] tokens = expression.split("(?<=[-+*/])|(?=[-+*/])");
        double result = Double.parseDouble(tokens[0]);
        for (int i = 1; i < tokens.length; i += 2) {
            char operator = tokens[i].charAt(0);
            double operand = Double.parseDouble(tokens[i+1]);
            switch (operator) {
                case '+': result += operand; break;
                case '-': result -= operand; break;
                case '*': result *= operand; break;
                case '/':
                    if (operand == 0) {
                        throw new ArithmeticException("Division by Zero");
                    }
                    result /= operand;
                    break;
            }
        }
        return result;
    }

    private boolean isValidExpression(String expression) {
        return expression.matches("([-+*/]?\\d+)+([-+*/]\\d+)*");
    }

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

这个计算器支持四则运算、小数点、清除、计算等功能，并且还有一个复选框可以选择是否四舍五入到整数。可以根据需要进一步修改和完善。