效果如下

代码实现

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

public class SimpleCalculator {
    private JFrame frame;
    private JTextField numField1;
    private JTextField numField2;
    private JTextField resultField;
    private JButton addButton;
    private JButton subtractButton;
    private JButton multiplyButton;
    private JButton divideButton;

    public SimpleCalculator() {
        frame = new JFrame("简易计算器");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new GridLayout(5, 1));
        frame.setResizable(false); // Disable maximizing

        JPanel inputPanel = new JPanel();
        numField1 = new JTextField(5);
        numField2 = new JTextField(5);
        resultField = new JTextField(5);
        resultField.setEditable(false);
        inputPanel.add(new JLabel("Number 1:"));
        inputPanel.add(numField1);
        inputPanel.add(new JLabel("Number 2:"));
        inputPanel.add(numField2);
        inputPanel.add(new JLabel("Result:"));
        inputPanel.add(resultField);

        JPanel buttonPanel = new JPanel();
        addButton = new JButton("+");
        subtractButton = new JButton("-");
        multiplyButton = new JButton("*");
        divideButton = new JButton("/");
        addButton.addActionListener(new OperationListener("+"));
        subtractButton.addActionListener(new OperationListener("-"));
        multiplyButton.addActionListener(new OperationListener("*"));
        divideButton.addActionListener(new OperationListener("/"));
        buttonPanel.add(addButton);
        buttonPanel.add(subtractButton);
        buttonPanel.add(multiplyButton);
        buttonPanel.add(divideButton);

        frame.add(inputPanel);
        frame.add(buttonPanel);

        frame.pack();
        frame.setLocationRelativeTo(null); // Place the frame in the center of the screen
        frame.setVisible(true);
    }

    private class OperationListener implements ActionListener {
        private String operation;

        public OperationListener(String operation) {
            this.operation = operation;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            double num1 = Double.parseDouble(numField1.getText());
            double num2 = Double.parseDouble(numField2.getText());
            double result = 0;

            switch (operation) {
                case "+":
                    result = num1 + num2;
                    break;
                case "-":
                    result = num1 - num2;
                    break;
                case "*":
                    result = num1 * num2;
                    break;
                case "/":
                    if (num2 != 0) {
                        result = num1 / num2;
                    } else {
                        JOptionPane.showMessageDialog(frame, "Cannot divide by zero!");
                        return;
                    }
                    break;
            }

            resultField.setText(String.valueOf(result));
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(SimpleCalculator::new);
    }
}