用java编写一个简易的计算器，要求能进行加减乘除运算，通过鼠标点击按键交互，并使用边界布局，还要有归零按键

以下是一个简单的Java计算器程序，实现了加减乘除和归零功能，并使用了边界布局。

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

public class Calculator extends JFrame implements ActionListener {
    private JButton btn0, btn1, btn2, btn3, btn4, btn5, btn6, btn7, btn8, btn9;
    private JButton btnAdd, btnSub, btnMul, btnDiv, btnClear, btnEquals;
    private JTextField txtResult;

    private double num1, num2;
    private String op = "";

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

        // create buttons
        btn0 = new JButton("0");
        btn1 = new JButton("1");
        btn2 = new JButton("2");
        btn3 = new JButton("3");
        btn4 = new JButton("4");
        btn5 = new JButton("5");
        btn6 = new JButton("6");
        btn7 = new JButton("7");
        btn8 = new JButton("8");
        btn9 = new JButton("9");
        btnAdd = new JButton("+");
        btnSub = new JButton("-");
        btnMul = new JButton("*");
        btnDiv = new JButton("/");
        btnClear = new JButton("C");
        btnEquals = new JButton("=");

        // create text field
        txtResult = new JTextField(20);
        txtResult.setEditable(false);

        // set layout
        setLayout(new BorderLayout());

        // add components to the frame
        JPanel panel1 = new JPanel();
        panel1.setLayout(new GridLayout(4, 3));
        panel1.add(btn1);
        panel1.add(btn2);
        panel1.add(btn3);
        panel1.add(btn4);
        panel1.add(btn5);
        panel1.add(btn6);
        panel1.add(btn7);
        panel1.add(btn8);
        panel1.add(btn9);
        panel1.add(btnClear);
        panel1.add(btn0);
        panel1.add(btnEquals);

        JPanel panel2 = new JPanel();
        panel2.setLayout(new GridLayout(4, 1));
        panel2.add(btnAdd);
        panel2.add(btnSub);
        panel2.add(btnMul);
        panel2.add(btnDiv);

        JPanel panel3 = new JPanel();
        panel3.setLayout(new FlowLayout());
        panel3.add(txtResult);

        add(panel1, BorderLayout.CENTER);
        add(panel2, BorderLayout.EAST);
        add(panel3, BorderLayout.NORTH);

        // add action listeners to the buttons
        btn0.addActionListener(this);
        btn1.addActionListener(this);
        btn2.addActionListener(this);
        btn3.addActionListener(this);
        btn4.addActionListener(this);
        btn5.addActionListener(this);
        btn6.addActionListener(this);
        btn7.addActionListener(this);
        btn8.addActionListener(this);
        btn9.addActionListener(this);
        btnAdd.addActionListener(this);
        btnSub.addActionListener(this);
        btnMul.addActionListener(this);
        btnDiv.addActionListener(this);
        btnClear.addActionListener(this);
        btnEquals.addActionListener(this);

        // set frame properties
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(250, 250);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        String button = e.getActionCommand();

        if (button.equals("C")) { // clear
            txtResult.setText("");
            num1 = 0;
            num2 = 0;
            op = "";
        } else if (button.equals("+")) { // addition
            num1 = Double.parseDouble(txtResult.getText());
            op = "+";
            txtResult.setText("");
        } else if (button.equals("-")) { // subtraction
            num1 = Double.parseDouble(txtResult.getText());
            op = "-";
            txtResult.setText("");
        } else if (button.equals("*")) { // multiplication
            num1 = Double.parseDouble(txtResult.getText());
            op = "*";
            txtResult.setText("");
        } else if (button.equals("/")) { // division
            num1 = Double.parseDouble(txtResult.getText());
            op = "/";
            txtResult.setText("");
        } else if (button.equals("=")) { // equals
            num2 = Double.parseDouble(txtResult.getText());
            if (op.equals("+")) {
                txtResult.setText(Double.toString(num1 + num2));
            } else if (op.equals("-")) {
                txtResult.setText(Double.toString(num1 - num2));
            } else if (op.equals("*")) {
                txtResult.setText(Double.toString(num1 * num2));
            } else if (op.equals("/")) {
                txtResult.setText(Double.toString(num1 / num2));
            }
        } else { // digit
            txtResult.setText(txtResult.getText() + button);
        }
    }

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

运行此程序，将会弹出一个简易的计算器界面。