javaupdatecalc

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

public class Calculator {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable()
{
public void run() {
CalculatorFrame frame = new CalculatorFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}
class CalculatorFrame extends JFrame {
public CalculatorFrame() {
setTitle(«Calculator 2.0»);
CalculatorPanel panel = new CalculatorPanel();
add(panel);
pack();
}
}
class CalculatorPanel extends JPanel {
public CalculatorPanel() {
setLayout(new BorderLayout());

result = 0;
lastCommand = «=»;
start = true;

display = new JButton(«0»);
display.setEnabled(false);
add(display, BorderLayout.NORTH);

ActionListener insert = new InsertAction();
ActionListener command = new CommandAction();

panel = new JPanel();
panel.setLayout(new GridLayout(4, 5));
addButton(«», command);
addButton(«7», insert);
addButton(«8», insert);
addButton(«9», insert);
addButton(«/», command);

addButton(«», command);
addButton(«4», insert);
addButton(«5», insert);
addButton(«6», insert);
addButton(«*», command);

addButton(«», command);
addButton(«1», insert);
addButton(«2», insert);
addButton(«3», insert);
addButton(«-«, command);

addButton(«Cl», 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);
}

private class InsertAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String input = event.getActionCommand();
if (start) {
display.setText(«»);
start = false;
}
display.setText(display.getText() + input);
}
}

private class CommandAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String command = event.getActionCommand();
if (start) {
if (command.equals(«Cl»)) {
// display.setText(command);
display.setText(«»);
start = false;
} else lastCommand = command;
} else {
calculate(Double.parseDouble(display.getText()));
lastCommand = command;
start = true;
}
}
}

public void calculate(double x) {

switch (lastCommand)
{
case «+»: result=Math.rint((result + x)*100)/100; break;
case «-«: result=Math.rint((result — x)*100)/100; break;
case «*»: result=Math.rint((result * x)*100)/100; break;
case «/»: result=Math.rint((result / x)*100)/100; break;
case «=»: result = x; break;

}
display.setText(«» + result);
}

private JButton display;
private JPanel panel;
private double result;
private String lastCommand;
private boolean start;
}