Java/Design Pattern/Command Pattern
Содержание
Command Pattern 2 in Java
<source lang="java">
//[C] 2002 Sun Microsystems, Inc.--- import java.awt.Container; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.io.Serializable; import java.util.Calendar; import java.util.Date; import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTextArea; import javax.swing.JTextField;
public class RunCommandPattern {
private static Calendar dateCreator = Calendar.getInstance();
public static void main(String [] arguments){
System.out.println("Example for the Command pattern");
System.out.println();
System.out.println("This sample will use a command class called");
System.out.println(" ChangeLocationCommand to update the location");
System.out.println(" of an Appointment object.");
System.out.println("The ChangeLocationCommand has the additional");
System.out.println(" ability to undo and redo commands, so it can");
System.out.println(" set the locaition back to its original value,");
System.out.println(" if desired.");
System.out.println();
System.out.println("Creating an Appointment for use in the demo");
Contact [] people = { new ContactImpl(), new ContactImpl() };
Appointment appointment = new Appointment("Java Twister Semi-Finals",
people, new LocationImpl(""), createDate(2001, 10, 31, 14, 30),
createDate(2001, 10, 31, 14, 31));
System.out.println("Creating the ChangeLocationCommand");
ChangeLocationCommand cmd = new ChangeLocationCommand();
cmd.setAppointment(appointment);
System.out.println("Creating the GUI");
CommandGui application = new CommandGui(cmd);
application.setAppointment(appointment);
cmd.setLocationEditor(application);
application.createGui();
}
public static Date createDate(int year, int month, int day, int hour, int minute){
dateCreator.set(year, month, day, hour, minute);
return dateCreator.getTime();
}
} class CommandGui implements ActionListener, LocationEditor{
private JFrame mainFrame;
private JTextArea display;
private JTextField updatedLocation;
private JButton update, undo, redo, exit;
private JPanel controlPanel, displayPanel, editorPanel;
private UndoableCommand command;
private Appointment appointment;
public CommandGui(UndoableCommand newCommand){
command = newCommand;
}
public void setAppointment(Appointment newAppointment){
appointment = newAppointment;
}
public void createGui(){
mainFrame = new JFrame("Command Pattern Example");
Container content = mainFrame.getContentPane();
content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));
editorPanel = new JPanel();
editorPanel.add(new JLabel("Location"));
updatedLocation = new JTextField(20);
editorPanel.add(updatedLocation);
content.add(editorPanel);
displayPanel = new JPanel();
display = new JTextArea(10, 40);
display.setEditable(false);
displayPanel.add(display);
content.add(displayPanel);
controlPanel = new JPanel();
update = new JButton("Update Location");
undo = new JButton("Undo Location");
redo = new JButton("Redo Location");
exit = new JButton("Exit");
controlPanel.add(update);
controlPanel.add(undo);
controlPanel.add(redo);
controlPanel.add(exit);
content.add(controlPanel);
update.addActionListener(this);
undo.addActionListener(this);
redo.addActionListener(this);
exit.addActionListener(this);
refreshDisplay();
mainFrame.addWindowListener(new WindowCloseManager());
mainFrame.pack();
mainFrame.setVisible(true);
}
public void actionPerformed(ActionEvent evt){
Object originator = evt.getSource();
if (originator == update){
executeCommand();
}
if (originator == undo){
undoCommand();
}
if (originator == redo){
redoCommand();
}
else if (originator == exit){
exitApplication();
}
}
private class WindowCloseManager extends WindowAdapter{
public void windowClosing(WindowEvent evt){
exitApplication();
}
}
public Location getNewLocation(){
return new LocationImpl(updatedLocation.getText());
}
private void executeCommand(){
command.execute();
refreshDisplay();
}
private void undoCommand(){
command.undo();
refreshDisplay();
}
private void redoCommand(){
command.redo();
refreshDisplay();
}
private void refreshDisplay(){
display.setText(appointment.toString());
}
private void exitApplication(){
System.exit(0);
}
} interface Command{
public void execute();
} interface Contact extends Serializable{
public static final String SPACE = " "; public String getFirstName(); public String getLastName(); public String getTitle(); public String getOrganization(); public void setFirstName(String newFirstName); public void setLastName(String newLastName); public void setTitle(String newTitle); public void setOrganization(String newOrganization);
} class ContactImpl implements Contact{
private String firstName;
private String lastName;
private String title;
private String organization;
public static final String EOL_STRING =
System.getProperty("line.separator");
public ContactImpl(){ }
public ContactImpl(String newFirstName, String newLastName,
String newTitle, String newOrganization){
firstName = newFirstName;
lastName = newLastName;
title = newTitle;
organization = newOrganization;
}
public String getFirstName(){ return firstName; }
public String getLastName(){ return lastName; }
public String getTitle(){ return title; }
public String getOrganization(){ return organization; }
public void setFirstName(String newFirstName){ firstName = newFirstName; }
public void setLastName(String newLastName){ lastName = newLastName; }
public void setTitle(String newTitle){ title = newTitle; }
public void setOrganization(String newOrganization){ organization = newOrganization; }
public String toString(){
return firstName + " " + lastName;
}
} class Appointment{
private String reason;
private Contact[] contacts;
private Location location;
private Date startDate;
private Date endDate;
public Appointment(String reason, Contact[] contacts, Location location, Date startDate, Date endDate){
this.reason = reason;
this.contacts = contacts;
this.location = location;
this.startDate = startDate;
this.endDate = endDate;
}
public String getReason(){ return reason; }
public Contact[] getContacts(){ return contacts; }
public Location getLocation(){ return location; }
public Date getStartDate(){ return startDate; }
public Date getEndDate(){ return endDate; }
public void setLocation(Location location){ this.location = location; }
public String toString(){
return "Appointment:" + "\n Reason: " + reason +
"\n Location: " + location + "\n Start: " +
startDate + "\n End: " + endDate + "\n";
}
} interface Location extends Serializable{
public String getLocation(); public void setLocation(String newLocation);
} class ChangeLocationCommand implements UndoableCommand{
private Appointment appointment;
private Location oldLocation;
private Location newLocation;
private LocationEditor editor;
public Appointment getAppointment(){ return appointment; }
public void setAppointment(Appointment appointment){ this.appointment = appointment; }
public void setLocationEditor(LocationEditor locationEditor){ editor = locationEditor; }
public void execute(){
oldLocation = appointment.getLocation();
newLocation = editor.getNewLocation();
appointment.setLocation(newLocation);
}
public void undo(){
appointment.setLocation(oldLocation);
}
public void redo(){
appointment.setLocation(newLocation);
}
} interface LocationEditor{
public Location getNewLocation();
} class LocationImpl implements Location{
private String location;
public LocationImpl(){ }
public LocationImpl(String newLocation){
location = newLocation;
}
public String getLocation(){ return location; }
public void setLocation(String newLocation){ location = newLocation; }
public String toString(){ return location; }
} interface UndoableCommand extends Command{
public void undo(); public void redo();
}
</source>
Command Pattern - Example: FTP GUI
<source lang="java">
/* Software Architecture Design Patterns in Java by Partha Kuchana Auerbach Publications
- /
import java.awt.BorderLayout; import java.awt.Container; import java.awt.GridBagConstraints; import java.awt.GridBagLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyEvent; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.DefaultListModel; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JList; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.ListSelectionModel; import javax.swing.SwingUtilities; import javax.swing.UIManager; import com.sun.java.swing.plaf.windows.WindowsLookAndFeel; public class FTPGUI extends JFrame {
public static final String newline = "\n";
public static final String UPLOAD = "Upload";
public static final String DOWNLOAD = "Download";
public static final String DELETE = "Delete";
public static final String EXIT = "Exit";
private JPanel pnlFTPUI;
private JList localList;
private JList remoteList;
private DefaultListModel defLocalList, defRemoteList;
private UploadButton btnUpload;
private DownloadButton btnDownload;
private DeleteButton btnDelete;
public FTPGUI() throws Exception {
super("Command Pattern - Example");
// Create controls
defLocalList = new DefaultListModel();
defRemoteList = new DefaultListModel();
localList = new JList(defLocalList);
remoteList = new JList(defRemoteList);
pnlFTPUI = new JPanel();
localList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
localList.setSelectedIndex(-1);
JScrollPane spLocalList = new JScrollPane(localList);
remoteList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
remoteList.setSelectedIndex(-1);
JScrollPane spRemoteList = new JScrollPane(remoteList);
//Create Labels
JLabel lblLocalList = new JLabel("Local List:");
JLabel lblRemoteList = new JLabel("Remote List:");
JLabel lblSpacer = new JLabel(" ");
//Create buttons
btnUpload = new UploadButton(FTPGUI.UPLOAD);
btnUpload.setMnemonic(KeyEvent.VK_U);
btnDownload = new DownloadButton(FTPGUI.DOWNLOAD);
btnDownload.setMnemonic(KeyEvent.VK_N);
btnDelete = new DeleteButton(FTPGUI.DELETE);
btnDelete.setMnemonic(KeyEvent.VK_D);
ExitButton btnExit = new ExitButton(FTPGUI.EXIT);
btnExit.setMnemonic(KeyEvent.VK_X);
buttonHandler vf = new buttonHandler();
btnUpload.addActionListener(vf);
btnDownload.addActionListener(vf);
btnDelete.addActionListener(vf);
btnExit.addActionListener(vf);
JPanel lstPanel = new JPanel();
GridBagLayout gridbag2 = new GridBagLayout();
lstPanel.setLayout(gridbag2);
GridBagConstraints gbc2 = new GridBagConstraints();
lstPanel.add(lblLocalList);
lstPanel.add(lblRemoteList);
lstPanel.add(spLocalList);
lstPanel.add(spRemoteList);
lstPanel.add(lblSpacer);
gbc2.gridx = 0;
gbc2.gridy = 0;
gridbag2.setConstraints(lblLocalList, gbc2);
gbc2.gridx = 1;
gbc2.gridy = 0;
gridbag2.setConstraints(lblSpacer, gbc2);
gbc2.gridx = 5;
gbc2.gridy = 0;
gridbag2.setConstraints(lblRemoteList, gbc2);
gbc2.gridx = 0;
gbc2.gridy = 1;
gridbag2.setConstraints(spLocalList, gbc2);
gbc2.gridx = 5;
gbc2.gridy = 1;
gridbag2.setConstraints(spRemoteList, gbc2);
//-----------------------------------
//For layout purposes, put the buttons in a separate panel
JPanel buttonPanel = new JPanel();
//----------------------------------------------
GridBagLayout gridbag = new GridBagLayout();
buttonPanel.setLayout(gridbag);
GridBagConstraints gbc = new GridBagConstraints();
buttonPanel.add(lstPanel);
buttonPanel.add(btnUpload);
buttonPanel.add(btnDownload);
buttonPanel.add(btnDelete);
buttonPanel.add(btnExit);
gbc.insets.top = 5;
gbc.insets.bottom = 5;
gbc.insets.left = 5;
gbc.insets.right = 5;
gbc.anchor = GridBagConstraints.WEST;
gbc.gridx = 1;
gbc.gridy = 0;
gridbag.setConstraints(btnUpload, gbc);
gbc.gridx = 2;
gbc.gridy = 0;
gridbag.setConstraints(btnDownload, gbc);
gbc.gridx = 3;
gbc.gridy = 0;
gridbag.setConstraints(btnDelete, gbc);
gbc.gridx = 4;
gbc.gridy = 0;
gridbag.setConstraints(btnExit, gbc);
gbc.gridx = 0;
gbc.gridy = 1;
gridbag.setConstraints(lstPanel, gbc);
gbc.anchor = GridBagConstraints.EAST;
gbc.insets.left = 2;
gbc.insets.right = 2;
gbc.insets.top = 40;
//****************************************************
//Add the buttons and the log to the frame
Container contentPane = getContentPane();
contentPane.add(lstPanel, BorderLayout.CENTER);
contentPane.add(buttonPanel, BorderLayout.SOUTH);
initialize();
try {
UIManager.setLookAndFeel(new WindowsLookAndFeel());
SwingUtilities.updateComponentTreeUI(FTPGUI.this);
} catch (Exception ex) {
System.out.println(ex);
}
}
private void initialize() {
// fill some test data here into the listbox.
defLocalList.addElement("first.html");
defLocalList.addElement("second.html");
defLocalList.addElement("third.html");
defLocalList.addElement("fourth.html");
defLocalList.addElement("fifth.html");
defLocalList.addElement("Design Patterns 1.html");
defRemoteList.addElement("sixth.html");
defRemoteList.addElement("seventh.html");
defRemoteList.addElement("eighth.html");
defRemoteList.addElement("ninth.html");
defRemoteList.addElement("Design Patterns 2.html");
}
public static void main(String[] args) throws Exception {
JFrame frame = new FTPGUI();
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
//frame.pack();
frame.setSize(450, 300);
frame.setVisible(true);
}
class buttonHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
CommandInterface CommandObj = (CommandInterface) e.getSource();
CommandObj.processEvent();
}
}
interface CommandInterface {
public void processEvent();
}
class UploadButton extends JButton implements CommandInterface {
public void processEvent() {
int index = localList.getSelectedIndex();
String selectedItem = localList.getSelectedValue().toString();
((DefaultListModel) localList.getModel()).remove(index);
((DefaultListModel) remoteList.getModel()).addElement(selectedItem);
}
public UploadButton(String name) {
super(name);
}
}
class DownloadButton extends JButton implements CommandInterface {
public void processEvent() {
int index = remoteList.getSelectedIndex();
String selectedItem = remoteList.getSelectedValue().toString();
((DefaultListModel) remoteList.getModel()).remove(index);
((DefaultListModel) localList.getModel()).addElement(selectedItem);
}
public DownloadButton(String name) {
super(name);
}
}
class DeleteButton extends JButton implements CommandInterface {
public void processEvent() {
int index = localList.getSelectedIndex();
if (index >= 0) {
((DefaultListModel) localList.getModel()).remove(index);
}
index = remoteList.getSelectedIndex();
if (index >= 0) {
((DefaultListModel) remoteList.getModel()).remove(index);
}
}
public DeleteButton(String name) {
super(name);
}
}
class ExitButton extends JButton implements CommandInterface {
public void processEvent() {
System.exit(1);
}
public ExitButton(String name) {
super(name);
}
}
}// end of class
</source>
Command pattern in Java 1
<source lang="java">
/* The Design Patterns Java Companion Copyright (C) 1998, by James W. Cooper IBM Thomas J. Watson Research Center
- /
import java.awt.Button; import java.awt.Color; import java.awt.FileDialog; import java.awt.Frame; import java.awt.Menu; import java.awt.MenuBar; import java.awt.MenuItem; import java.awt.Panel; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; public class ActionCommand extends Frame {
Menu mnuFile;
MenuItem mnuOpen, mnuExit;
Button btnRed;
Panel p;
Frame fr;
//-----------------------------------------
public ActionCommand() {
super("Frame without commands");
fr = this; //sae cop of this frame
MenuBar mbar = new MenuBar();
setMenuBar(mbar);
mnuFile = new Menu("File", true);
mbar.add(mnuFile);
mnuOpen = new MenuItem("Open...");
mnuFile.add(mnuOpen);
mnuExit = new MenuItem("Exit");
mnuFile.add(mnuExit);
mnuOpen.addActionListener(new fileOpen());
mnuExit.addActionListener(new fileExit());
btnRed = new Button("Red");
p = new Panel();
add(p);
p.add(btnRed);
btnRed.addActionListener(new btnRed());
setBounds(100, 100, 200, 100);
setVisible(true);
}
//-----------------------------------------
private void exitClicked() {
System.exit(0);
}
//-----------------------------------------
static public void main(String argv[]) {
new ActionCommand();
}
//=====----====--inner classes---=====----
class fileOpen implements ActionListener {
public void actionPerformed(ActionEvent e) {
FileDialog fDlg = new FileDialog(fr, "Open a file", FileDialog.LOAD);
fDlg.show();
}
}
//-------------------------------------
class btnRed implements ActionListener {
public void actionPerformed(ActionEvent e) {
p.setBackground(Color.red);
}
}
//-------------------------------------
class fileExit implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
}
} //=====================================
</source>
Command pattern in Java 2
<source lang="java">
/* The Design Patterns Java Companion Copyright (C) 1998, by James W. Cooper IBM Thomas J. Watson Research Center
- /
import java.awt.Button; import java.awt.Color; import java.awt.FileDialog; import java.awt.Frame; import java.awt.Menu; import java.awt.MenuBar; import java.awt.MenuItem; import java.awt.Panel; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; interface Command {
public void Execute();
} public class TestCommand extends Frame implements ActionListener {
Menu mnuFile;
fileOpenCommand mnuOpen;
fileExitCommand mnuExit;
btnRedCommand btnRed;
Panel p;
Frame fr;
//-----------------------------------------
public TestCommand() {
super("Frame without commands");
fr = this; //save frame object
MenuBar mbar = new MenuBar();
setMenuBar(mbar);
mnuFile = new Menu("File", true);
mbar.add(mnuFile);
mnuOpen = new fileOpenCommand("Open...");
mnuFile.add(mnuOpen);
mnuExit = new fileExitCommand("Exit");
mnuFile.add(mnuExit);
mnuOpen.addActionListener(this);
mnuExit.addActionListener(this);
btnRed = new btnRedCommand("Red");
p = new Panel();
add(p);
p.add(btnRed);
btnRed.addActionListener(this);
setBounds(100, 100, 200, 100);
setVisible(true);
}
//-----------------------------------------
public void actionPerformed(ActionEvent e) {
Command obj = (Command) e.getSource();
obj.Execute();
}
//-----------------------------------------
static public void main(String argv[]) {
new TestCommand();
}
//====----====-----inner class----=====----
class btnRedCommand extends Button implements Command {
public btnRedCommand(String caption) {
super(caption);
}
public void Execute() {
p.setBackground(Color.red);
}
}
//------------------------------------------
class fileOpenCommand extends MenuItem implements Command {
public fileOpenCommand(String caption) {
super(caption);
}
public void Execute() {
FileDialog fDlg = new FileDialog(fr, "Open file");
fDlg.show();
}
}
//-------------------------------------------
class fileExitCommand extends MenuItem implements Command {
public fileExitCommand(String caption) {
super(caption);
}
public void Execute() {
System.exit(0);
}
}
} //==========================================
</source>
Command pattern in Java 3
<source lang="java">
/* The Design Patterns Java Companion Copyright (C) 1998, by James W. Cooper IBM Thomas J. Watson Research Center
- /
import java.awt.Button; import java.awt.Color; import java.awt.FileDialog; import java.awt.Frame; import java.awt.Menu; import java.awt.MenuBar; import java.awt.MenuItem; import java.awt.Panel; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; interface Command {
public void Execute();
} public class ExtrnCommand extends Frame implements ActionListener {
Menu mnuFile;
fileOpenCommand mnuOpen;
fileExitCommand mnuExit;
btnRedCommand btnRed;
Panel p;
Frame fr;
//-----------------------------------------
public ExtrnCommand() {
super("Frame with external commands");
fr = this; //save frame object
MenuBar mbar = new MenuBar();
setMenuBar(mbar);
mnuFile = new Menu("File", true);
mbar.add(mnuFile);
mnuOpen = new fileOpenCommand("Open...", this);
mnuFile.add(mnuOpen);
mnuExit = new fileExitCommand("Exit");
mnuFile.add(mnuExit);
mnuOpen.addActionListener(this);
mnuExit.addActionListener(this);
p = new Panel();
add(p);
btnRed = new btnRedCommand("Red", p);
p.add(btnRed);
btnRed.addActionListener(this);
setBounds(100, 100, 200, 100);
setVisible(true);
}
//-----------------------------------------
public void actionPerformed(ActionEvent e) {
Command obj = (Command) e.getSource();
obj.Execute();
}
//-----------------------------------------
static public void main(String argv[]) {
new ExtrnCommand();
}
} //========================================== class btnRedCommand extends Button implements Command {
Panel p;
public btnRedCommand(String caption, Panel pnl) {
super(caption);
p = pnl;
}
public void Execute() {
p.setBackground(Color.red);
}
} //------------------------------------------ class fileOpenCommand extends MenuItem implements Command {
Frame fr;
public fileOpenCommand(String caption, Frame frm) {
super(caption);
fr = frm;
}
public void Execute() {
FileDialog fDlg = new FileDialog(fr, "Open file");
fDlg.show();
}
} //------------------------------------------- class fileExitCommand extends MenuItem implements Command {
public fileExitCommand(String caption) {
super(caption);
}
public void Execute() {
System.exit(0);
}
}
</source>
Command pattern in Java 4
<source lang="java">
/* The Design Patterns Java Companion Copyright (C) 1998, by James W. Cooper IBM Thomas J. Watson Research Center
- /
import java.awt.Button; import java.awt.Color; import java.awt.FileDialog; import java.awt.Frame; import java.awt.Menu; import java.awt.MenuBar; import java.awt.MenuItem; import java.awt.Panel; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; public class InnerCommand extends Frame {
Menu mnuFile;
MenuItem mnuOpen, mnuExit;
Button btnRed;
Panel p;
Frame fr;
//-----------------------------------------
public InnerCommand() {
super("Frame without commands");
fr = this;
MenuBar mbar = new MenuBar();
setMenuBar(mbar);
mnuFile = new Menu("File", true);
mbar.add(mnuFile);
mnuOpen = new MenuItem("Open...");
mnuFile.add(mnuOpen);
mnuExit = new MenuItem("Exit");
mnuFile.add(mnuExit);
mnuOpen.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
FileDialog fDlg = new FileDialog(fr, "Open a file",
FileDialog.LOAD);
fDlg.show();
}
});
mnuExit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
});
btnRed = new Button("Red");
p = new Panel();
add(p);
p.add(btnRed);
btnRed.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
p.setBackground(Color.red);
}
});
setBounds(100, 100, 200, 100);
setVisible(true);
}
//-----------------------------------------
static public void main(String argv[]) {
new InnerCommand();
}
} //=====================================
</source>
Command pattern: Shopping
<source lang="java">
/* Software Architecture Design Patterns in Java by Partha Kuchana Auerbach Publications
- /
import java.util.HashMap; public class CommandTest {
public static void main(String[] args) {
//Add an item to the CD category
//create Receiver objects
Item CD = new Item("A Beautiful Mind");
Category catCD = new Category("CD");
//create the command object
CommandInterface command = new AddCommand(CD, catCD);
//create the invoker
ItemManager manager = new ItemManager();
//configure the invoker
//with the command object
manager.setCommand(command);
manager.process();
//Add an item to the CD category
CD = new Item("Duet");
catCD = new Category("CD");
command = new AddCommand(CD, catCD);
manager.setCommand(command);
manager.process();
//Add an item to the New Releases category
CD = new Item("Duet");
catCD = new Category("New Releases");
command = new AddCommand(CD, catCD);
manager.setCommand(command);
manager.process();
//Delete an item from the New Releases category
command = new DeleteCommand(CD, catCD);
manager.setCommand(command);
manager.process();
}
} class ItemManager {
CommandInterface command;
public void setCommand(CommandInterface c) {
command = c;
}
public void process() {
command.execute();
}
} class Item {
private HashMap categories;
private String desc;
public Item(String s) {
desc = s;
categories = new HashMap();
}
public String getDesc() {
return desc;
}
public void add(Category cat) {
categories.put(cat.getDesc(), cat);
}
public void delete(Category cat) {
categories.remove(cat.getDesc());
}
} class DeleteCommand implements CommandInterface {
Item item;
Category cat;
public DeleteCommand(Item i, Category c) {
item = i;
cat = c;
}
public void execute() {
item.delete(cat);
cat.delete(item);
}
} interface CommandInterface {
public void execute();
} class Category {
private HashMap items;
private String desc;
public Category(String s) {
desc = s;
items = new HashMap();
}
public String getDesc() {
return desc;
}
public void add(Item i) {
items.put(i.getDesc(), i);
System.out.println("Item "" + i.getDesc() + "" has been added to the ""
+ getDesc() + "" Category ");
}
public void delete(Item i) {
items.remove(i.getDesc());
System.out.println("Item "" + i.getDesc()
+ "" has been deleted from the "" + getDesc() + "" Category ");
}
} class AddCommand implements CommandInterface {
Item item;
Category cat;
public AddCommand(Item i, Category c) {
item = i;
cat = c;
}
public void execute() {
item.add(cat);
cat.add(item);
}
}
</source>
