Короче я уже это сам реализовал. Конечно не без помощи гугл.
Вот код:
| Код |
import java.awt.Color;
import java.awt.Container;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.LinkedList;
import javax.swing.BoxLayout;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
class CalculatorState {
CalculatorState(String numberDialed) {
this.numberDialed=numberDialed;
}
String numberDialed;
double memoryContent;
double currentResult;
}
abstract class CalculatorCommand {
protected Calculator calculator;
abstract void execute();
abstract void undo();
}
class CalculationCommand extends CalculatorCommand {
private String firstOperand;
private String operation;
CalculationCommand(String operation, String firstOperand, Calculator calculator) {
this.operation = operation;
this.firstOperand = firstOperand;
this.calculator = calculator;
}
void execute() {
calculator.performOperation(operation,firstOperand);
}
void undo() {
calculator.undoOperation(operation,firstOperand);
}
String getOperation() {
return operation;
}
}
class DialingCommand extends CalculatorCommand{
private String dialed;
DialingCommand(String dialed, Calculator calculator) {
this.dialed=dialed;
this.calculator = calculator;
}
void execute() {
calculator.dial(dialed);
}
void undo() {
calculator.undoDial(dialed);
}
}
class ClearCommand extends CalculatorCommand{
private String dialed;
ClearCommand(String dialed, Calculator calculator) {
this.dialed=dialed;
this.calculator = calculator;
}
void execute() {
calculator.clear();
}
void undo() {
calculator.undoClear(dialed);
}
}
class NumberButton extends JButton {
private int number;
public NumberButton(int number) {
super(Integer.toString(number));
this.number=number;
}
public int getNumber() {
return number;
}
}
class OperationButton extends JButton {
private String operation;
public OperationButton(String operation) {
super(operation);
this.operation=operation;
}
public String getOperation() {
return operation;
}
}
public class Calculator extends JApplet{
private CalculatorState current = new CalculatorState("");
private LinkedList<CalculatorCommand> commands = new LinkedList<CalculatorCommand>();
private CalculationCommand lastOperation;
private JLabel display = new JLabel();
void dial (String todial) {
current.numberDialed=current.numberDialed+todial;
display.setText(current.numberDialed);
}
void undoDial (String dialed) {
if (current.numberDialed.length()>dialed.length()) {
current.numberDialed=current.numberDialed.substring(0,current.numberDialed.length()-dialed.length());
}
else {
current.numberDialed="";
}
display.setText(current.numberDialed);
}
void performOperation(String operation, String firstOperand) {
if (operation == "+") {
current.numberDialed=Double.toString(Double.valueOf(current.numberDialed)+Double.valueOf(firstOperand));
}
else if (operation == "-") {
current.numberDialed=Double.toString(Double.valueOf(firstOperand)-Double.valueOf(current.numberDialed));
}
else if (operation == "*") {
current.numberDialed=Double.toString(Double.valueOf(current.numberDialed)*Double.valueOf(firstOperand));
}
else if (operation == "/") {
current.numberDialed=Double.toString(Double.valueOf(firstOperand)/Double.valueOf(current.numberDialed));
}
display.setText(current.numberDialed);
}
void undoOperation(String operation, String firstOperand) {
current.numberDialed=firstOperand;
display.setText(current.numberDialed);
}
void clear() {
if (current.numberDialed.length()>1) {
current.numberDialed=current.numberDialed.substring(0,current.numberDialed.length()-1);
}
else {
current.numberDialed="";
}
display.setText(current.numberDialed);
}
void undoClear(String dialed) {
current.numberDialed=dialed;
display.setText(current.numberDialed);
}
private ActionListener nbl = new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
CalculatorCommand cc = new DialingCommand(Integer.toString(((NumberButton)arg0.getSource()).getNumber()),Calculator.this);
commands.add(cc);
cc.execute();
}
};
private ActionListener obl = new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if (current.numberDialed.charAt(current.numberDialed.length()-1)=='.') {
current.numberDialed=current.numberDialed+"0";
}
CalculationCommand cc = new CalculationCommand(((OperationButton)arg0.getSource()).getOperation(),current.numberDialed,Calculator.this);
if (lastOperation != null) {
lastOperation.execute();
}
lastOperation=cc;
commands.add(cc);
if (cc.getOperation() != "=") {
current.numberDialed="";
}
display.setText(current.numberDialed);
}
};
private ActionListener pbl = new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if (! current.numberDialed.contains(".")) {
CalculatorCommand cc = new DialingCommand(".",Calculator.this);
commands.add(cc);
cc.execute();
}
}
};
private ActionListener ubl = new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if (!commands.isEmpty()) {
commands.removeLast().undo();
}
}
};
private ActionListener cbl = new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
ClearCommand cc = new ClearCommand(current.numberDialed, Calculator.this);
commands.add(cc);
cc.execute();
}
};
public void init() {
JButton nb[] = new NumberButton[10];
JPanel buttons = new JPanel(new GridLayout(4,4));
for (int i=7; i<=9 ; i++){
nb[i-1]=new NumberButton(i);
nb[i-1].addActionListener(nbl);
buttons.add(nb[i-1]);
}
OperationButton subb = new OperationButton("-");
subb.addActionListener(obl);
buttons.add(subb);
for (int i=4; i<=6 ; i++){
nb[i-1]=new NumberButton(i);
nb[i-1].addActionListener(nbl);
buttons.add(nb[i-1]);
}
OperationButton addb = new OperationButton("+");
addb.addActionListener(obl);
buttons.add(addb);
for (int i=1; i<=3 ; i++){
nb[i-1]=new NumberButton(i);
nb[i-1].addActionListener(nbl);
buttons.add(nb[i-1]);
}
OperationButton mulb = new OperationButton("*");
mulb.addActionListener(obl);
buttons.add(mulb);
OperationButton pointb = new OperationButton(".");
pointb.addActionListener(pbl);
buttons.add(pointb);
nb[9]=new NumberButton(0);
nb[9].addActionListener(nbl);
buttons.add(nb[9]);
OperationButton equalb = new OperationButton("=");
equalb.addActionListener(obl);
buttons.add(equalb);
OperationButton divb = new OperationButton("/");
divb.addActionListener(obl);
buttons.add(divb);
Container cp = getContentPane();
cp.setLayout(new BoxLayout(cp,BoxLayout.Y_AXIS));
JPanel displaybg = new JPanel();
displaybg.setBackground(new Color((float)1,(float)1,(float)1));
displaybg.add(display);
JButton clb=new JButton("Clear");
clb.addActionListener(cbl);
JPanel lowBtnPanel = new JPanel();
lowBtnPanel.add(clb);
JButton undob = new JButton("Undo");
undob.addActionListener(ubl);
lowBtnPanel.add(undob);
cp.add(displaybg);
cp.add(buttons);
cp.add(lowBtnPanel);
}
public static void main(String[] args) {
JApplet calculator = new Calculator();
JFrame mainFrame = new JFrame("Simple Calculator");
mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mainFrame.getContentPane().add(calculator);
mainFrame.setSize(200,250);
calculator.init();
calculator.start();
mainFrame.setVisible(true);
}
}
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На студенческую работу сойдет  |