用Java设计一个简单的计算器，要求要有相应的图形界面，有相加，相减，相除，相乘与清 除功能，并且为按钮设计相应的事件

以下是基于Java Swing的简单计算器实现，包含加、减、乘、除和清除功能：

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

public class SimpleCalculator extends JFrame {

    private JTextField inputField;
    private JLabel errorLabel;

    private double currentResult;
    private String currentOperator;

    public SimpleCalculator() {
        super("Simple Calculator");

        //初始化当前结果和操作符
        currentResult = 0;
        currentOperator = "";

        //创建输入框和错误提示标签
        inputField = new JTextField(10);
        inputField.setEditable(false);
        inputField.setHorizontalAlignment(JTextField.RIGHT);

        errorLabel = new JLabel("");
        errorLabel.setForeground(Color.RED);
        errorLabel.setHorizontalAlignment(JLabel.RIGHT);

        //创建数字按钮
        JButton[] digitButtons = new JButton[10];
        for (int i = 0; i < 10; i++) {
            digitButtons[i] = new JButton(Integer.toString(i));
            digitButtons[i].addActionListener(new DigitButtonActionListener(i));
        }

        //创建操作符按钮
        JButton addButton = new JButton("+");
        addButton.addActionListener(new OperatorButtonActionListener("+"));
        JButton subtractButton = new JButton("-");
        subtractButton.addActionListener(new OperatorButtonActionListener("-"));
        JButton multiplyButton = new JButton("*");
        multiplyButton.addActionListener(new OperatorButtonActionListener("*"));
        JButton divideButton = new JButton("/");
        divideButton.addActionListener(new OperatorButtonActionListener("/"));

        //创建清除按钮
        JButton clearButton = new JButton("C");
        clearButton.addActionListener(new ClearButtonActionListener());

        //创建面板并添加组件
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();

        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.gridwidth = 4;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        panel.add(inputField, gbc);

        gbc.gridx = 0;
        gbc.gridy = 1;
        gbc.gridwidth = 4;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        panel.add(errorLabel, gbc);

        gbc.gridx = 0;
        gbc.gridy = 2;
        gbc.gridwidth = 1;
        panel.add(digitButtons[7], gbc);

        gbc.gridx = 1;
        gbc.gridy = 2;
        panel.add(digitButtons[8], gbc);

        gbc.gridx = 2;
        gbc.gridy = 2;
        panel.add(digitButtons[9], gbc);

        gbc.gridx = 3;
        gbc.gridy = 2;
        panel.add(addButton, gbc);

        gbc.gridx = 0;
        gbc.gridy = 3;
        panel.add(digitButtons[4], gbc);

        gbc.gridx = 1;
        gbc.gridy = 3;
        panel.add(digitButtons[5], gbc);

        gbc.gridx = 2;
        gbc.gridy = 3;
        panel.add(digitButtons[6], gbc);

        gbc.gridx = 3;
        gbc.gridy = 3;
        panel.add(subtractButton, gbc);

        gbc.gridx = 0;
        gbc.gridy = 4;
        panel.add(digitButtons[1], gbc);

        gbc.gridx = 1;
        gbc.gridy = 4;
        panel.add(digitButtons[2], gbc);

        gbc.gridx = 2;
        gbc.gridy = 4;
        panel.add(digitButtons[3], gbc);

        gbc.gridx = 3;
        gbc.gridy = 4;
        panel.add(multiplyButton, gbc);

        gbc.gridx = 0;
        gbc.gridy = 5;
        panel.add(digitButtons[0], gbc);

        gbc.gridx = 1;
        gbc.gridy = 5;
        panel.add(clearButton, gbc);

        gbc.gridx = 2;
        gbc.gridy = 5;
        panel.add(new JLabel(), gbc);

        gbc.gridx = 3;
        gbc.gridy = 5;
        panel.add(divideButton, gbc);

        //添加面板到窗口
        add(panel);

        //设置窗口属性
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(300, 200);
        setLocationRelativeTo(null); //居中显示
        setResizable(false);
        setVisible(true);
    }

    private class DigitButtonActionListener implements ActionListener {
        private int digit;

        public DigitButtonActionListener(int digit) {
            this.digit = digit;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            //将数字添加到输入框
            inputField.setText(inputField.getText() + Integer.toString(digit));
            errorLabel.setText("");
        }
    }

    private class OperatorButtonActionListener implements ActionListener {
        private String operator;

        public OperatorButtonActionListener(String operator) {
            this.operator = operator;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            try {
                //将当前输入的数字转换为double类型
                double number = Double.parseDouble(inputField.getText());

                //根据当前操作符进行计算
                switch (currentOperator) {
                    case "+":
                        currentResult += number;
                        break;
                    case "-":
                        currentResult -= number;
                        break;
                    case "*":
                        currentResult *= number;
                        break;
                    case "/":
                        currentResult /= number;
                        break;
                    default:
                        currentResult = number;
                        break;
                }

                //更新当前操作符和输入框的值
                currentOperator = operator;
                inputField.setText(Double.toString(currentResult));
                errorLabel.setText("");
            } catch (NumberFormatException ex) {
                //输入的不是数字，显示错误提示
                errorLabel.setText("Invalid input");
            }
        }
    }

    private class ClearButtonActionListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            //清空输入框和当前结果，重置操作符
            inputField.setText("");
            currentResult = 0;
            currentOperator = "";
            errorLabel.setText("");
        }
    }

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

运行该程序，将会出现一个简单的计算器界面。用户可以通过点击数字按钮输入数字，通过点击加、减、乘、除按钮进行计算，通过点击清除按钮清空输入框和当前结果。

注：此代码为示例代码，仅供参考，实际应用中需要根据需求进行修改和完善。