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;
}
界面：
