用java设计一个简易的计算器，要求如下：要使用java的GUI设计出计算器界面；通过界面按钮，可以进行加减乘除运算，并能讲结果显示在界面中；计算可以有小数点，和正负整数的计算；要有清零功能

好的，我可以为您提供一个简单的Java计算器程序示例，如下所示：

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

public class Calculator implements ActionListener {

    JFrame frame;
    JTextField textField;
    JButton[] numberButtons = new JButton[10];
    JButton[] functionButtons = new JButton[9];
    JButton addButton, subButton, mulButton, divButton;
    JButton decimalButton, equalsButton, clearButton, negativeButton;
    JPanel panel;

    double num1 = 0, num2 = 0, result = 0;
    char operator;

    Calculator() {
        frame = new JFrame("Calculator");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 400);
        frame.setLayout(null);

        textField = new JTextField();
        textField.setBounds(30, 40, 240, 30);
        textField.setEditable(false);

        addButton = new JButton("+");
        subButton = new JButton("-");
        mulButton = new JButton("*");
        divButton = new JButton("/");
        decimalButton = new JButton(".");
        equalsButton = new JButton("=");
        clearButton = new JButton("C");
        negativeButton = new JButton("+/-");

        functionButtons[0] = addButton;
        functionButtons[1] = subButton;
        functionButtons[2] = mulButton;
        functionButtons[3] = divButton;
        functionButtons[4] = decimalButton;
        functionButtons[5] = equalsButton;
        functionButtons[6] = clearButton;
        functionButtons[7] = negativeButton;

        for (int i = 0; i < 10; i++) {
            numberButtons[i] = new JButton(String.valueOf(i));
        }

        panel = new JPanel();
        panel.setBounds(30, 100, 240, 240);
        panel.setLayout(new GridLayout(4, 4, 10, 10));

        panel.add(numberButtons[1]);
        panel.add(numberButtons[2]);
        panel.add(numberButtons[3]);
        panel.add(addButton);
        panel.add(numberButtons[4]);
        panel.add(numberButtons[5]);
        panel.add(numberButtons[6]);
        panel.add(subButton);
        panel.add(numberButtons[7]);
        panel.add(numberButtons[8]);
        panel.add(numberButtons[9]);
        panel.add(mulButton);
        panel.add(decimalButton);
        panel.add(numberButtons[0]);
        panel.add(equalsButton);
        panel.add(divButton);

        for (int i = 0; i < 8; i++) {
            functionButtons[i].addActionListener(this);
            functionButtons[i].setFont(new Font("Verdana", Font.BOLD, 16));
            functionButtons[i].setFocusable(false);
        }

        for (int i = 0; i < 10; i++) {
            numberButtons[i].addActionListener(this);
            numberButtons[i].setFont(new Font("Verdana", Font.BOLD, 16));
            numberButtons[i].setFocusable(false);
        }

        textField.setFont(new Font("Verdana", Font.PLAIN, 16));
        textField.setHorizontalAlignment(JTextField.RIGHT);
        textField.setBorder(BorderFactory.createLineBorder(Color.BLACK));

        panel.setBorder(BorderFactory.createLineBorder(Color.BLACK));

        frame.add(textField);
        frame.add(panel);

        frame.setVisible(true);
    }

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

    @Override
    public void actionPerformed(ActionEvent e) {
        for (int i = 0; i < 10; i++) {
            if (e.getSource() == numberButtons[i]) {
                textField.setText(textField.getText() + String.valueOf(i));
            }
        }

        if (e.getSource() == decimalButton) {
            textField.setText(textField.getText() + ".");
        }

        if (e.getSource() == addButton) {
            num1 = Double.parseDouble(textField.getText());
            operator = '+';
            textField.setText("");
        }

        if (e.getSource() == subButton) {
            num1 = Double.parseDouble(textField.getText());
            operator = '-';
            textField.setText("");
        }

        if (e.getSource() == mulButton) {
            num1 = Double.parseDouble(textField.getText());
            operator = '*';
            textField.setText("");
        }

        if (e.getSource() == divButton) {
            num1 = Double.parseDouble(textField.getText());
            operator = '/';
            textField.setText("");
        }

        if (e.getSource() == equalsButton) {
            num2 = Double.parseDouble(textField.getText());
            switch (operator) {
                case '+':
                    result = num1 + num2;
                    break;
                case '-':
                    result = num1 - num2;
                    break;
                case '*':
                    result = num1 * num2;
                    break;
                case '/':
                    result = num1 / num2;
                    break;
            }
            textField.setText(String.valueOf(result));
            num1 = result;
        }

        if (e.getSource() == clearButton) {
            textField.setText("");
        }

        if (e.getSource() == negativeButton) {
            double temp = Double.parseDouble(textField.getText());
            temp *= -1;
            textField.setText(String.valueOf(temp));
        }
    }
}

这个Java计算器程序可以执行加、减、乘、除、清零、正负数、小数点和等于的操作。运行程序后，您将看到一个计算器界面，您可以通过按钮进行计算，并将结果显示在界面中。