提问：编写一个简单的Java程序，模拟计算器的功能。

网友回答：

程序参考：

import java.awt.*;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JPanel;

public class Calculater  {

public static void main(String[] args)

{

new Calculater();

}

Calculater() {

EventQueue.invokeLater(new Runnable() {

public void run() {

// TODO Auto-generated method stub

CalculatorFrame frame = new CalculatorFrame();

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.setSize(500, 400);

frame.setVisible(true);

}

});

}

class CalculatorFrame extends JFrame {

public CalculatorFrame() {

CalculatorPanel panels = new CalculatorPanel();

setTitle("Calculator");

add(panels);

pack();

}

}

class CalculatorPanel extends JPanel {

public CalculatorPanel() {

setLayout(new BorderLayout());

lastCommand = "=";

start = true;

// add the display

display = new JButton();

display.setEnabled(false);

add(display, BorderLayout.NORTH);

ActionListener insert = new InsertAction();

ActionListener command = new CommandAction();

// Add buttons in a 4 * 4 grid

panel = new JPanel();

panel.setLayout(new GridLayout(4, 4));

addButton("7", insert);

addButton("8", insert);

addButton("9", insert);

addButton("/", command);

addButton("4", insert);

addButton("5", insert);

addButton("6", insert);

addButton("*", command);

addButton("1", insert);

addButton("2", insert);

addButton("3", insert);

addButton("-", command);

addButton("0", insert);

addButton(".", insert);

addButton("=", command);

addButton("+", command);

add(panel, BorderLayout.CENTER);

}

}

private void addButton(String label, ActionListener listener) {

JButton button = new JButton(label);

button.addActionListener(listener);

panel.add(button);

}

// InsertAction

private class InsertAction implements ActionListener {

public void actionPerformed(ActionEvent e) {

// TODO Auto-generated method stub

String input = e.getActionCommand();

if (start) {

display.setText("");

start = false;

}

display.setText(display.getText() + input);

}

}

// CommandAction

private class CommandAction implements ActionListener {

public void actionPerformed(ActionEvent event) {

String command = event.getActionCommand();

if (start) {

if (command.equals("-")) {

display.setText(command);

start = false;

} else {

lastCommand = command;

}

} else {

calculate(Double.parseDouble(display.getText()));

lastCommand = command;

start = true;

}

}

}

// calculate

public void calculate(double x) {

if (lastCommand.equals("+")) {

result += x;

} else if (lastCommand.equals("-")) {

result -= x;

} else if (lastCommand.equals("*")) {

result *= x;

} else if (lastCommand.equals("+")) {

result *= x;

} else if (lastCommand.equals("/")) {

result /= x;

} else if (lastCommand.equals("=")) {

result = x;

}

display.setText("" + result);

}

private JButton display;

private JPanel panel;

private double result;

private String lastCommand;

private boolean start;

}

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