Java/Design Pattern/FlightWeight Pattern

Flyweight Pattern in Java

//[C] 2002 Sun Microsystems, Inc.---
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
public class RunFlyweightPattern {
    public static void main(String [] arguments) throws java.io.IOException{
        System.out.println("Example for the Flyweight pattern");
        System.out.println();
        System.out.println("In this sample, State objects are shared between multiple");
        System.out.println(" parts of the PIM. Two lists, representing a Contact list");
        System.out.println(" and an Address Book, are used for the demonstration.");
        System.out.println(" The State objects - CleanState and DirtyState - represent");
        System.out.println(" the Flyweight objects in this example.");
        System.out.println();
        
        System.out.println("Creating ManagedList objects to hold Contacts and Addresses");
        ManagedList contactList = new ManagedList(Contact.class);
        ManagedList addressList = new ManagedList(Address.class);
        System.out.println();
        
        System.out.println("Printing the State for the application");
        printPIMState();
        System.out.println();
        
        System.out.println("Editing the Address and Contact lists");
        StateFactory.getCurrentState().edit(State.CONTACTS);
        StateFactory.getCurrentState().edit(State.ADDRESSES);
        contactList.addItem(new ContactImpl("f", "l", "t", "o"));
        addressList.addItem(new AddressImpl("d", "s", "c", "st", "z"));
        System.out.println("Printing the State for the application");
        printPIMState();
        System.out.println();
        
        System.out.println("Saving the Contact list");
        StateFactory.getCurrentState().save(new java.io.File("contacts.ser"), contactList.getItems(), State.CONTACTS);
        System.out.println("Printing the State for the application");
        printPIMState();
        System.out.println();
        
        System.out.println("Saving the Address list");
        StateFactory.getCurrentState().save(new java.io.File("addresses.ser"), addressList.getItems(), State.ADDRESSES);
        System.out.println("Printing the State for the application");
        printPIMState();
    }
    
    private static void printPIMState(){
        System.out.println("  Current State of the PIM: " + StateFactory.getCurrentState().getClass());
        System.out.println("  Object ID: " + StateFactory.getCurrentState().hashCode());
        System.out.println();
    }
}
interface State{
    public static final int CONTACTS = 1;
    public static final int ADDRESSES = 2;
    public static final int MAXIMUM_STATE_VALUE = 2;
    public void save(File f, Serializable s, int type) throws IOException;
    public void edit(int type);
}
class StateFactory {
    public static final State CLEAN = new CleanState();
    public static final State DIRTY = new DirtyState();
    private static State currentState = CLEAN;
    
    public static State getCurrentState(){
        return currentState;
    }
    
    public static void setCurrentState(State state){
        currentState = state;
    }
}
class CleanState implements State{
    public void save(File file, Serializable s, int type) throws IOException{ }
    public void edit(int type){
        StateFactory.setCurrentState(StateFactory.DIRTY);
        ((DirtyState)StateFactory.DIRTY).incrementStateValue(type);
    }
}
class DirtyState implements State{
    private int stateFlags;
    
    public void save(File file, Serializable data, int stateType) throws IOException{
        FileOutputStream fos = new FileOutputStream(file);
        ObjectOutputStream out = new ObjectOutputStream(fos);
        out.writeObject(data);
        decrementStateValue(stateType);
        if (stateFlags == 0){
            StateFactory.setCurrentState(StateFactory.CLEAN);
        }
    }
    public void edit(int type){
        incrementStateValue(type);
    }
    
    public void incrementStateValue(int stateType){
        if ((stateType > 0) && (stateType <= MAXIMUM_STATE_VALUE)){
            stateFlags = stateFlags | stateType;
        }
    }
    public void decrementStateValue(int stateType){
        if ((stateType > 0) && (stateType <= MAXIMUM_STATE_VALUE)){
            stateFlags = stateFlags ^ stateType;
        }
    }
}
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 AddressImpl implements Address{
    private String type;
    private String description;
    private String street;
    private String city;
    private String state;
    private String zipCode;
    public static final String HOME = "home";
    public static final String WORK = "work";
    
    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;
    }
}
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 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 + SPACE + lastName;
    }
}
class ManagedList{
    private ArrayList elements = new ArrayList();
    private Class classType;
    
    public ManagedList(){ }
    public ManagedList(Class newClassType){
        classType = newClassType;
    }
    
    public void setClassType(Class newClassType){
        classType = newClassType;
    }
    
    public void addItem(Object item){
        if ((item != null) && (classType.isInstance(item))){
            elements.add(item);
        } else {
            elements.add(item);
        }
    }
    
    public void removeItem(Object item){
        elements.remove(item);
    }
    
    public ArrayList getItems(){
        return elements;
    }
}