Java/Design Pattern/Command Pattern

Command Pattern 2 in 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();
}

Command Pattern - Example: FTP GUI

/*
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

Command pattern in Java 1

/*
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);
    }
  }
}
//=====================================

Command pattern in Java 2

/*
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);
    }
  }
}
//==========================================

Command pattern in Java 3

/*
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);
  }
}

Command pattern in Java 4

/*
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();
  }
}
//=====================================

Command pattern: Shopping

/*
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);
  }
}