用java的GUI设计一个简易的计算器，可以进行四则运算：加、减、乘、除等（限于十进制下），应具有相应的界面

好的，我可以为您提供一个简单的Java GUI计算器示例。以下是代码：

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

public class Calculator extends JFrame implements ActionListener {
    private JTextField inputField;
    private String operator = "";
    private double num1 = 0, num2 = 0;

    public Calculator() {
        setTitle("计算器");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(300, 300);
        setLocationRelativeTo(null);
        setLayout(new BorderLayout());

        inputField = new JTextField();
        inputField.setHorizontalAlignment(JTextField.RIGHT);
        inputField.setEditable(false);
        add(inputField, BorderLayout.NORTH);

        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(4, 4));
        add(buttonPanel, BorderLayout.CENTER);

        String[] buttonTexts = {"7", "8", "9", "+",
                                "4", "5", "6", "-",
                                "1", "2", "3", "*",
                                "0", ".", "=", "/"};
        for (String text : buttonTexts) {
            JButton button = new JButton(text);
            button.addActionListener(this);
            buttonPanel.add(button);
        }

        setVisible(true);
    }

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

    @Override
    public void actionPerformed(ActionEvent e) {
        String buttonText = e.getActionCommand();

        switch (buttonText) {
            case "+":
            case "-":
            case "*":
            case "/":
                operator = buttonText;
                num1 = Double.parseDouble(inputField.getText());
                inputField.setText("");
                break;
            case "=":
                num2 = Double.parseDouble(inputField.getText());
                double result = calculate();
                inputField.setText(String.valueOf(result));
                operator = "";
                break;
            default:
                inputField.setText(inputField.getText() + buttonText);
                break;
        }
    }

    private double calculate() {
        switch (operator) {
            case "+":
                return num1 + num2;
            case "-":
                return num1 - num2;
            case "*":
                return num1 * num2;
            case "/":
                return num1 / num2;
            default:
                return 0;
        }
    }
}

这个计算器界面比较简单，只有一个文本框和一个按钮面板。按钮面板使用了GridLayout布局，可以自动排列按钮。在按钮的ActionListener中，我们根据不同的按钮执行不同的操作，例如输入数字、选择运算符、计算结果等。