编写程序实现一个简单的运算器，要求至少实现加、减、乘、除四则运算，运算器功能界面排布尽量接近实际的运算器，数字输入通过界面上的数字按钮进行。java

以下是一个基本的Java程序，实现了加、减、乘、除四则运算：

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

public class Calculator extends JFrame implements ActionListener {

    // 定义界面组件
    private JTextField display;
    private JButton button0, button1, button2, button3, button4, button5, button6, button7, button8, button9;
    private JButton buttonPlus, buttonMinus, buttonMultiply, buttonDivide, buttonEqual, buttonClear;

    // 定义变量
    private double prevValue, curValue;
    private String operator;

    public Calculator() {
        // 初始化变量
        prevValue = 0.0;
        curValue = 0.0;
        operator = "";

        // 创建界面组件
        display = new JTextField();
        display.setEditable(false);
        display.setHorizontalAlignment(JTextField.RIGHT);

        button0 = new JButton("0");
        button1 = new JButton("1");
        button2 = new JButton("2");
        button3 = new JButton("3");
        button4 = new JButton("4");
        button5 = new JButton("5");
        button6 = new JButton("6");
        button7 = new JButton("7");
        button8 = new JButton("8");
        button9 = new JButton("9");

        buttonPlus = new JButton("+");
        buttonMinus = new JButton("-");
        buttonMultiply = new JButton("*");
        buttonDivide = new JButton("/");
        buttonEqual = new JButton("=");
        buttonClear = new JButton("C");

        // 添加事件监听器
        button0.addActionListener(this);
        button1.addActionListener(this);
        button2.addActionListener(this);
        button3.addActionListener(this);
        button4.addActionListener(this);
        button5.addActionListener(this);
        button6.addActionListener(this);
        button7.addActionListener(this);
        button8.addActionListener(this);
        button9.addActionListener(this);

        buttonPlus.addActionListener(this);
        buttonMinus.addActionListener(this);
        buttonMultiply.addActionListener(this);
        buttonDivide.addActionListener(this);
        buttonEqual.addActionListener(this);
        buttonClear.addActionListener(this);

        // 创建界面布局
        JPanel panel1 = new JPanel(new GridLayout(1, 1));
        panel1.add(display);

        JPanel panel2 = new JPanel(new GridLayout(4, 4));
        panel2.add(button7);
        panel2.add(button8);
        panel2.add(button9);
        panel2.add(buttonDivide);
        panel2.add(button4);
        panel2.add(button5);
        panel2.add(button6);
        panel2.add(buttonMultiply);
        panel2.add(button1);
        panel2.add(button2);
        panel2.add(button3);
        panel2.add(buttonMinus);
        panel2.add(button0);
        panel2.add(buttonClear);
        panel2.add(buttonEqual);
        panel2.add(buttonPlus);

        // 添加组件到窗口
        Container contentPane = getContentPane();
        contentPane.setLayout(new BorderLayout());
        contentPane.add(panel1, BorderLayout.NORTH);
        contentPane.add(panel2, BorderLayout.CENTER);

        // 设置窗口属性
        setTitle("Calculator");
        setSize(300, 300);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);
    }

    // 处理按钮点击事件
    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();
        if (command.equals("C")) {
            display.setText("");
            prevValue = 0.0;
            curValue = 0.0;
            operator = "";
        } else if (command.equals("+")) {
            prevValue = Double.parseDouble(display.getText());
            display.setText("");
            operator = "+";
        } else if (command.equals("-")) {
            prevValue = Double.parseDouble(display.getText());
            display.setText("");
            operator = "-";
        } else if (command.equals("*")) {
            prevValue = Double.parseDouble(display.getText());
            display.setText("");
            operator = "*";
        } else if (command.equals("/")) {
            prevValue = Double.parseDouble(display.getText());
            display.setText("");
            operator = "/";
        } else if (command.equals("=")) {
            curValue = Double.parseDouble(display.getText());
            if (operator.equals("+")) {
                display.setText(Double.toString(prevValue + curValue));
            } else if (operator.equals("-")) {
                display.setText(Double.toString(prevValue - curValue));
            } else if (operator.equals("*")) {
                display.setText(Double.toString(prevValue * curValue));
            } else if (operator.equals("/")) {
                if (curValue == 0.0) {
                    display.setText("Error");
                } else {
                    display.setText(Double.toString(prevValue / curValue));
                }
            }
            prevValue = 0.0;
            curValue = 0.0;
            operator = "";
        } else {
            display.setText(display.getText() + command);
        }
    }

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

这个程序创建了一个窗口，其中包含了一个文本框和一些按钮。每个按钮都有一个事件监听器，当用户点击按钮时，程序会根据按钮的标签执行相应的操作。