用Java语言写一个计算器界面，实现如下计算器界面，并为按钮添加事件处理：当按钮被点击时将对应字符显示到顶部文本框中

这里提供一个使用Java Swing编写的简单计算器界面代码，可以实现基本的加减乘除运算，你可以根据需要进行修改：

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

public class CalculatorUI extends JFrame implements ActionListener {
    private static final long serialVersionUID = 1L;
    private JTextField resultText;
    private JButton numButton[] = new JButton[10];
    private JButton opButton[] = new JButton[6];
    private String operator = "";
    private double num1 = 0, num2 = 0, result = 0;

    public CalculatorUI() {
        setTitle("Calculator");
        setSize(300, 350);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);

        // 创建组件
        resultText = new JTextField();
        resultText.setEditable(false);
        resultText.setHorizontalAlignment(JTextField.RIGHT);

        for (int i = 0; i < numButton.length; i++) {
            numButton[i] = new JButton(String.valueOf(i));
            numButton[i].addActionListener(this);
        }

        opButton[0] = new JButton("+");
        opButton[1] = new JButton("-");
        opButton[2] = new JButton("*");
        opButton[3] = new JButton("/");
        opButton[4] = new JButton("C");
        opButton[5] = new JButton("=");

        for (int i = 0; i < opButton.length; i++) {
            opButton[i].addActionListener(this);
        }

        // 布局
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(4, 4, 5, 5));
        buttonPanel.add(numButton[7]);
        buttonPanel.add(numButton[8]);
        buttonPanel.add(numButton[9]);
        buttonPanel.add(opButton[0]);
        buttonPanel.add(numButton[4]);
        buttonPanel.add(numButton[5]);
        buttonPanel.add(numButton[6]);
        buttonPanel.add(opButton[1]);
        buttonPanel.add(numButton[1]);
        buttonPanel.add(numButton[2]);
        buttonPanel.add(numButton[3]);
        buttonPanel.add(opButton[2]);
        buttonPanel.add(numButton[0]);
        buttonPanel.add(opButton[4]);
        buttonPanel.add(opButton[5]);
        buttonPanel.add(opButton[3]);

        // 添加组件
        add(resultText, BorderLayout.NORTH);
        add(buttonPanel, BorderLayout.CENTER);
    }

    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();
        if (command.charAt(0) >= '0' && command.charAt(0) <= '9') {
            resultText.setText(resultText.getText() + command);
        } else if (command.equals("+")) {
            operator = "+";
            num1 = Double.parseDouble(resultText.getText());
            resultText.setText("");
        } else if (command.equals("-")) {
            operator = "-";
            num1 = Double.parseDouble(resultText.getText());
            resultText.setText("");
        } else if (command.equals("*")) {
            operator = "*";
            num1 = Double.parseDouble(resultText.getText());
            resultText.setText("");
        } else if (command.equals("/")) {
            operator = "/";
            num1 = Double.parseDouble(resultText.getText());
            resultText.setText("");
        } else if (command.equals("C")) {
            resultText.setText("");
        } else if (command.equals("=")) {
            num2 = Double.parseDouble(resultText.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("/")) {
                if (num2 == 0) {
                    resultText.setText("Error");
                    return;
                } else {
                    result = num1 / num2;
                }
            }
            resultText.setText(String.valueOf(result));
        }
    }

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

运行程序后会弹出一个计算器窗口，可以进行数字和运算符的输入和计算，效果如下：