Java/Design Pattern/Memento Pattern

Memento Pattern 2

   <source lang="java">

//[C] 2002 Sun Microsystems, Inc.--- import java.io.Serializable; import java.util.ArrayList; public class RunMementoPattern {

 public static void main(String[] arguments) {
   System.out.println("Example for the Memento pattern");
   System.out.println();
   System.out
       .println("This example will use the AddressBook to demonstrate");
   System.out
       .println(" how a Memento can be used to save and restore state.");
   System.out
       .println("The AddressBook has an inner class, AddressBookMemento,");
   System.out
       .println(" that is used to store the AddressBook state... in this");
   System.out.println(" case, its internal list of contacts.");
   System.out.println();
   System.out.println("Creating the AddressBook");
   AddressBook book = new AddressBook();
   System.out.println("Adding Contact entries for the AddressBook");
   book.addContact(new ContactImpl("Peter", "Taggart", "Commander",
       "NSEA Protector", new AddressImpl()));
   book.addContact(new ContactImpl("Tawny", "Madison", "Lieutenant",
       "NSEA Protector", new AddressImpl()));
   book.addContact(new ContactImpl("Dr.", "Lazarus", "Dr.",
       "NSEA Protector", new AddressImpl()));
   book.addContact(new ContactImpl("Tech Sargent", "Chen", "Tech Sargent",
       "NSEA Protector", new AddressImpl()));
   System.out.println("Contacts added. Current Contact list:");
   System.out.println(book);
   System.out.println();
   System.out.println("Creating a Memento for the address book");
   Object memento = book.getMemento();
   System.out
       .println("Now that a Memento exists, it can be used to restore");
   System.out
       .println(" the state of this AddressBook object, or to set the");
   System.out.println(" state of a new AddressBook.");
   System.out.println();
   System.out.println("Creating new entries for the AddressBook");
   book.removeAllContacts();
   book.addContact(new ContactImpl("Jason", "Nesmith", "",
       "Actor"s Guild", new AddressImpl()));
   book.addContact(new ContactImpl("Gwen", "DeMarco", "", "Actor"s Guild",
       new AddressImpl()));
   book.addContact(new ContactImpl("Alexander", "Dane", "",
       "Actor"s Guild", new AddressImpl()));
   book.addContact(new ContactImpl("Fred", "Kwan", "", "Actor"s Guild",
       new AddressImpl()));
   System.out.println("New Contacts added. Current Contact list:");
   System.out.println(book);
   System.out.println();
   System.out
       .println("Using the Memento object to restore the AddressBook");
   System.out.println(" to its original state.");
   book.setMemento(memento);
   System.out.println("AddressBook restored. Current Contact list:");
   System.out.println(book);
 }

} 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);

} interface Address extends Serializable {

 public static final String EOL_STRING = System
     .getProperty("line.separator");
 public static final String SPACE = " ";
 public static final String COMMA = ",";
 public String getType();
 public String getDescription();
 public String getStreet();
 public String getCity();
 public String getState();
 public String getZipCode();
 public void setType(String newType);
 public void setDescription(String newDescription);
 public void setStreet(String newStreet);
 public void setCity(String newCity);
 public void setState(String newState);
 public void setZipCode(String newZip);

} class ContactImpl implements Contact {

 private String firstName;
 private String lastName;
 private String title;
 private String organization;
 private Address address;
 public ContactImpl() {
 }
 public ContactImpl(String newFirstName, String newLastName,
     String newTitle, String newOrganization, Address newAddress) {
   firstName = newFirstName;
   lastName = newLastName;
   title = newTitle;
   organization = newOrganization;
   address = newAddress;
 }
 public String getFirstName() {
   return firstName;
 }
 public String getLastName() {
   return lastName;
 }
 public String getTitle() {
   return title;
 }
 public String getOrganization() {
   return organization;
 }
 public Address getAddress() {
   return address;
 }
 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 void setAddress(Address newAddress) {
   address = newAddress;
 }
 public String toString() {
   return firstName + " " + lastName;
 }

} class AddressImpl implements Address {

 private String type;
 private String description;
 private String street;
 private String city;
 private String state;
 private String zipCode;
 public AddressImpl() {
 }
 public AddressImpl(String newDescription, String newStreet, String newCity,
     String newState, String newZipCode) {
   description = newDescription;
   street = newStreet;
   city = newCity;
   state = newState;
   zipCode = newZipCode;
 }
 public String getType() {
   return type;
 }
 public String getDescription() {
   return description;
 }
 public String getStreet() {
   return street;
 }
 public String getCity() {
   return city;
 }
 public String getState() {
   return state;
 }
 public String getZipCode() {
   return zipCode;
 }
 public void setType(String newType) {
   type = newType;
 }
 public void setDescription(String newDescription) {
   description = newDescription;
 }
 public void setStreet(String newStreet) {
   street = newStreet;
 }
 public void setCity(String newCity) {
   city = newCity;
 }
 public void setState(String newState) {
   state = newState;
 }
 public void setZipCode(String newZip) {
   zipCode = newZip;
 }
 public String toString() {
   return street + EOL_STRING + city + COMMA + SPACE + state + SPACE
       + zipCode + EOL_STRING;
 }

} class AddressBook {

 private ArrayList contacts = new ArrayList();
 public Object getMemento() {
   return new AddressBookMemento(contacts);
 }
 public void setMemento(Object object) {
   if (object instanceof AddressBookMemento) {
     AddressBookMemento memento = (AddressBookMemento) object;
     contacts = memento.state;
   }
 }
 private class AddressBookMemento {
   private ArrayList state;
   private AddressBookMemento(ArrayList contacts) {
     this.state = contacts;
   }
 }
 public AddressBook() {
 }
 public AddressBook(ArrayList newContacts) {
   contacts = newContacts;
 }
 public void addContact(Contact contact) {
   if (!contacts.contains(contact)) {
     contacts.add(contact);
   }
 }
 public void removeContact(Contact contact) {
   contacts.remove(contact);
 }
 public void removeAllContacts() {
   contacts = new ArrayList();
 }
 public ArrayList getContacts() {
   return contacts;
 }
 public String toString() {
   return contacts.toString();
 }

}

      </source>
   
  
 
  

Memento pattern in Java

   <source lang="java">

/* The Design Patterns Java Companion Copyright (C) 1998, by James W. Cooper IBM Thomas J. Watson Research Center

• /

import java.awt.BorderLayout; import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Rectangle; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import java.awt.event.MouseMotionAdapter; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.util.Vector; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JToggleButton; import javax.swing.JToolBar; public class MemDraw extends JFrame implements ActionListener {

 JToolBar tbar;
 Mediator med;
 
 public MemDraw() {
   super("Memento Drawing");
   addWindowListener(new WindowAdapter() {
     public void windowClosing(WindowEvent e) {
       System.exit(0);
     }
   });
   JPanel jp = new JPanel();
   getContentPane().add(jp);
   med = new Mediator();
   jp.setLayout(new BorderLayout());
   tbar = new JToolBar();
   jp.add("North", tbar);
   RectButton rect = new RectButton(this, med);
   tbar.add(rect);
   UndoButton undo = new UndoButton(this, med);
   tbar.add(undo);
   tbar.addSeparator();
   ClearButton clr = new ClearButton(this, med);
   tbar.add(clr);
   JCanvas canvas = new JCanvas(med);
   jp.add("Center", canvas);
   MouseApp map = new MouseApp(med);
   canvas.addMouseListener(map);
   MouseMoveApp mvap = new MouseMoveApp(med);
   canvas.addMouseMotionListener(mvap);
   setSize(new Dimension(400, 300));
   setVisible(true);
 }
 
 public void actionPerformed(ActionEvent e) {
   Command comd = (Command) e.getSource();
   comd.Execute();
 }
 
 static public void main(String[] argv) {
   new MemDraw();
 }

} //============================== class MouseApp extends MouseAdapter {

 Mediator med;
 public MouseApp(Mediator md) {
   super();
   med = md;
 }
 public void mousePressed(MouseEvent e) {
   med.createRect(e.getX(), e.getY());
 }
 public void mouseReleased(MouseEvent e) {
   med.rememberPosition();
 }

}

class MouseMoveApp extends MouseMotionAdapter {

 Mediator med;
 public MouseMoveApp(Mediator md) {
   super();
   med = md;
 }
 public void mouseDragged(MouseEvent e) {
   med.drag(e.getX(), e.getY());
 }

} class ClearButton extends JButton implements Command {

 Mediator med;
 public ClearButton(ActionListener act, Mediator md) {
   super("C");
   setToolTipText("Clear");
   addActionListener(act);
   med = md;
 }
 
 public void Execute() {
   med.clear();
 }

} class JCanvas extends JPanel {

 Mediator med;
 public JCanvas(Mediator md) {
   med = md;
   med.registerCanvas(this);
   setBackground(Color.white);
 }
 public void paint(Graphics g) {
   super.paint(g);
   med.reDraw(g);
 }

} class Mediator {

 boolean startRect;
 boolean rectSelected;
 Vector drawings;
 Vector undoList;
 RectButton rect;
 JPanel canvas;
 visRectangle selectedRectangle;
 public Mediator() {
   startRect = false;
   rectSelected = false;
   drawings = new Vector();
   undoList = new Vector();
 }
 
 public void startRectangle() {
   startRect = true;
 }
 
 public void createRect(int x, int y) {
   unpick(); //make sure no rectangle is selected
   if (startRect) //if rect button is depressed
   {
     Integer count = new Integer(drawings.size());
     undoList.addElement(count); //Save previous drawing list size
     visRectangle v = new visRectangle(x, y);
     drawings.addElement(v); //add new element to list
     startRect = false; //done with this rectangle
     rect.setSelected(false); //unclick button
     canvas.repaint();
   } else
     pickRect(x, y); //if not pressed look for rect to select
 }
 
 public void registerRectButton(RectButton rb) {
   rect = rb;
 }
 
 public void registerCanvas(JPanel p) {
   canvas = p;
 }
 
 private void unpick() {
   rectSelected = false;
   if (selectedRectangle != null) {
     selectedRectangle.setSelected(false);
     selectedRectangle = null;
     repaint();
   }
 }
 
 public void rememberPosition() {
   if (rectSelected) {
     Memento m = new Memento(selectedRectangle);
     undoList.addElement(m);
   }
 }
 
 public void pickRect(int x, int y) {
   //save current selected rectangle to avoid double save of undo
   visRectangle lastPick = selectedRectangle;
   unpick();
   for (int i = 0; i < drawings.size(); i++) {
     visRectangle v = (visRectangle) drawings.elementAt(i);
     if (v.contains(x, y)) //did click inside a rectangle
     {
       selectedRectangle = v; //save it
       rectSelected = true;
       if (selectedRectangle != lastPick) //but don"t save twice
         rememberPosition();
       v.setSelected(true); //turn on handles
       repaint(); //and redraw
     }
   }
 }
 
 public void clear() {
   drawings = new Vector();
   undoList = new Vector();
   rectSelected = false;
   selectedRectangle = null;
   repaint();
 }
 
 private void repaint() {
   canvas.repaint();
 }
 
 public void drag(int x, int y) {
   if (rectSelected) {
     if (selectedRectangle.contains(x, y)) {
       selectedRectangle.move(x, y);
       repaint();
     }
   }
 }
 
 public void reDraw(Graphics g) {
   g.setColor(Color.black);
   for (int i = 0; i < drawings.size(); i++) {
     visRectangle v = (visRectangle) drawings.elementAt(i);
     v.draw(g);
   }
 }
 
 public void undo() {
   if (undoList.size() > 0) {
     //get last element in undo list
     Object obj = undoList.lastElement();
     undoList.removeElement(obj); //and remove it
     //if this is an Integer, the last action was a new rectangle
     if (obj instanceof Integer) {
       //remove last created rectangle
       Object drawObj = drawings.lastElement();
       drawings.removeElement(drawObj);
     }
     //if this is a Memento, the last action was a move
     if (obj instanceof Memento) {
       //get the Memento
       Memento m = (Memento) obj;
       m.restore(); //and restore the old position
     }
     repaint();
   }
 }

} interface Command {

 public void Execute();

} class RectButton extends JToggleButton implements Command {

 Mediator med;
 public RectButton(ActionListener act, Mediator md) {
   super("R");
   //setSize(new Dimension(25,25));
   //setBorder(new EmptyBorder(5,5,5,5));
   setToolTipText("Draw rectangle");
   addActionListener(act);
   med = md;
   med.registerRectButton(this);
 }
 
 public void Execute() {
   if (isSelected()) {
     med.startRectangle();
   }
 }

} class UndoButton extends JButton implements Command {

 Mediator med;
 public UndoButton(ActionListener act, Mediator md) {
   super("U");
   //setSize(new Dimension(25,25));
   //setBorder(new EmptyBorder(5,5,5,5));
   setToolTipText("Undo");
   addActionListener(act);
   med = md;
 }
 
 public void Execute() {
   med.undo();
 }

} class visRectangle {

 int x, y, w, h;
 Rectangle rect;
 boolean selected;
 public visRectangle(int xpt, int ypt) {
   x = xpt;
   y = ypt;
   w = 40;
   h = 30;
   saveAsRect();
 }
 
 public void setSelected(boolean b) {
   selected = b;
 }
 
 private void saveAsRect() {
   rect = new Rectangle(x - w / 2, y - h / 2, w, h);
 }
 
 public void draw(Graphics g) {
   g.drawRect(x, y, w, h);
   if (selected) {
     g.fillRect(x + w / 2, y - 2, 4, 4);
     g.fillRect(x - 2, y + h / 2, 4, 4);
     g.fillRect(x + w / 2, y + h - 2, 4, 4);
     g.fillRect(x + w - 2, y + h / 2, 4, 4);
   }
 }
 
 public boolean contains(int x, int y) {
   return rect.contains(x, y);
 }
 
 public void move(int xpt, int ypt) {
   x = xpt;
   y = ypt;
   saveAsRect();
 }

} //=============================================== class Memento {

 visRectangle rect;
 //saved fields- remember internal fields
 //of the specified visual rectangle
 int x, y, w, h;
 public Memento(visRectangle r) {
   rect = r;
   x = rect.x;
   y = rect.y;
   w = rect.w;
   h = rect.h;
 }
 
 public void restore() {
   //restore the internal state of
   //the specified rectangle
   rect.x = x;
   rect.y = y;
   rect.h = h;
   rect.w = w;
 }

}

      </source>