CREATIONAL PATTERN

Prototype pattern deals with encapsulating cloning process. As the name suggests, it is used to create prototypes by cloning, not real objects from scratch. This pattern can be used in situation where creating new object of class from scratch is costly operation, so instead it is cloned from existing objects. For example, for ome process need to prepare List of all account numbers associated with bank and customer are millions. In this case, it is costly to prepare such list object by reading through database, so such list is copied from existing list object.

Account.java

public class Account 
implements Cloneable{
	

	private String accountNo;
	private String mailId;
	private String firstName,lastName;
	
	public String getAccountNo() {
		return accountNo;
	}

	public void setAccountNo(String accountNo) {
		this.accountNo = accountNo;
	}

	public String getMailId() {
		return mailId;
	}

	public void setMailId(String mailId) {
		this.mailId = mailId;
	}

	public String getFirstName() {

		return firstName;
	}

	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	public Account(String accountNo, String firstName, String lastName, String mailId) {
		// TODO Auto-generated constructor stub
		this.accountNo=accountNo;
		this.firstName = firstName;
		this.lastName = lastName;
		this.mailId = mailId;
	}

	
}

AccountHolderList.java

import java.io.File;
import java.util.ArrayList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class AccountHolderList implements Cloneable{

	private ArrayList accounts;
	
	public ArrayList getAccountsList(){
		return accounts;
	}
	
	public AccountHolderList() {
		// TODO Auto-generated constructor stub
		accounts = new ArrayList();
	}

	public void loadListFromDatabase(){
		//load accounts data from xml based database
		
		try   
		{  
		//creating a constructor of file class and parsing an XML file  
		File file = new File("src/AccountsDatabase.xml");  
		//an instance of factory that gives a document builder  
		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();  
		//an instance of builder to parse the specified xml file  
		DocumentBuilder db = dbf.newDocumentBuilder();  
		Document doc = db.parse(file);  
		doc.getDocumentElement().normalize();  
		System.out.println("Root element: " + doc.getDocumentElement().getNodeName());  
		NodeList nodeList = doc.getElementsByTagName("Account");  
		// nodeList is not iterable, so we are using for loop  
		for (int itr = 0; itr < nodeList.getLength(); itr++)   
		{  
		Node node = nodeList.item(itr);  
		System.out.println("\nNode Name :" + node.getNodeName());  
		if (node.getNodeType() == Node.ELEMENT_NODE)   
		{  
		Element eElement = (Element) node;
		String accountNo = eElement.getElementsByTagName("accountNo").item(0).getTextContent();
		String firstName = eElement.getElementsByTagName("firstname").item(0).getTextContent();
		String lastName  = eElement.getElementsByTagName("lastname").item(0).getTextContent();
		String mailId = eElement.getElementsByTagName("mailId").item(0).getTextContent();
		System.out.println("accountNo: "+ accountNo);  
		System.out.println("First Name: "+ firstName);  
		System.out.println("Last Name: "+ lastName);  
		System.out.println("mail Id: "+ mailId);  
		Account accountData = new Account(accountNo, firstName, lastName, mailId);
		accounts.add(accountData);
		}  
		}  
		}   
		catch (Exception e)   
		{  
		e.printStackTrace();  
		}  
		System.out.println("Loaded accounts from database ::"+accounts.size());
	}
	
	public Object clone() {
	      Object clone = null;
	      try {
	         clone = super.clone();
	      } catch (CloneNotSupportedException e) {
	         e.printStackTrace();
	      }
	      return clone;
	  }
}

PrototypePatternDemo.java

import java.util.ArrayList;
import java.util.Iterator;

public class PrototypePatternDemo {

	public static AccountHolderList accountHolderList;
	static{
		
		//load accounts from database at time of system initiliazation
		accountHolderList = new AccountHolderList();
		accountHolderList.loadListFromDatabase();
	}
	
	public PrototypePatternDemo() {
		// TODO Auto-generated constructor stub
	}

	public static void main(String[] args) {
		
		//clone accounts List for sending mail, instrad of reading from database
		AccountHolderList clonedList = (AccountHolderList)accountHolderList.clone();
		
		ArrayList accList =clonedList.getAccountsList(); 
		Iterator listItr = accList.iterator();
		
		Account acc;
		while(listItr.hasNext()){
			acc = (Account)listItr.next();
			System.out.println("wished Happy New year to ::" + acc.getMailId()); 
		}
		
	}

}

Output

CREATIONAL PATTERN

As the name suggests, builder pattern is about encapsulating logic for building of complex composite object by composing small, simple objects. Sometimes, every real-world entity cannot be directly created as Class. For example Lunchset.

Item.java

public interface Item {

public String getName();
public String getCost();
	
}

Cola.java

public class Cola implements Item {

	public Cola() {
		// TODO Auto-generated constructor stub
	}

	@Override
	public String getName() {
		// TODO Auto-generated method stub
		return "Coca Cola";
	}

	@Override
	public String getCost() {
		// TODO Auto-generated method stub
		return "20 INR";
	}

}

Sprite.java

public class Sprite implements Item {

	public Sprite() {
		// TODO Auto-generated constructor stub
	}

	@Override
	public String getName() {
		// TODO Auto-generated method stub
		return "Sprite";
	}

	@Override
	public String getCost() {
		// TODO Auto-generated method stub
		return "30 INR";
	}

}

ChickenBurger.java

public class ChickenBurger implements Item {

	public ChickenBurger() {
		// TODO Auto-generated constructor stub
	}

	@Override
	public String getName() {
		// TODO Auto-generated method stub
		return "Chicken Burger";
	}

	@Override
	public String getCost() {
		// TODO Auto-generated method stub
		return "50 INR";
	}

}

VegBurger.java

public class VegBurger implements Item {

	public VegBurger() {
		// TODO Auto-generated constructor stub
	}

	@Override
	public String getName() {
		// TODO Auto-generated method stub
		return "Veg Burger";
	}

	@Override
	public String getCost() {
		// TODO Auto-generated method stub
		return "40 INR";
	}

}

LunchSet.java

import java.util.ArrayList;
import java.util.Iterator;

public class LunchSet {

	ArrayList items ;
	
	public LunchSet() {
		// TODO Auto-generated constructor stub
		items  = new ArrayList();
	}

	public void printBills(){
		if(items==null)
		{
			System.out.println("Pls make order, set is empty");
		}
		
		Iterator itr = items.iterator();
		Item item;
		while(itr.hasNext()){
			item = (Item)itr.next();
			System.out.println(item.getName() + ", cost :" + item.getCost());
		}
	}

	public void addItem(Item item){
		items.add(item);
		return;
	}
}

BuilderPatternDemo.java

public class BuilderPatternDemo {

	public BuilderPatternDemo() {
		// TODO Auto-generated constructor stub
	}

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		//I want Chicken burger and Coke
		LunchSet set1 = new LunchSet();
		set1.addItem(new ChickenBurger());
		set1.addItem(new Cola());
		System.out.println("Here is your set, pls pay bills as below");
		set1.printBills();
		
		
		//I want Veg Burger and Sprite
		LunchSet set2 = new LunchSet();
		set2.addItem(new VegBurger());
		set2.addItem(new Sprite());
		System.out.println("Here is your set, pls pay bills as below");
		set2.printBills();
		
		
		
		
	}

}

CREATIONAL PATTERN.

Factory pattern deals with encapsulating logic for creation of objects. Suppose in banking system banker want to provide the passbook to new customer. In this case surely passbooks are not created in every branch of bank but manufacturing of passbooks would be carried out by factories & dispatched to branches on request. In this business model, all operations & logistics are managed by factories for passbooks production & branches are totally unaware or not interested to know how factory manage it. In this case if want to modify construction of object, we will have to change only factory class, not other classes like banker or customer

Passbook.java

public class Passbook {

	private String color;
	private int pageSize;
	
	public Passbook(String color, int pageSize) {
		// TODO Auto-generated constructor stub
		this.color = color;
		this.pageSize=pageSize;
	}

	public String getColor() {
		return color;
	}
	public int getPageSize() {
		return pageSize;
	}


}

PassbookFactory.java

import java.util.HashMap;
import java.util.Map;

public class PassbookFactory {
	
	private static Map colorCodeMap;
	private static Map sizeCodeMap;
	
	
	public PassbookFactory() {
		
		if(colorCodeMap==null){
			colorCodeMap = new HashMap();
			colorCodeMap.put(1,"Orange");
			colorCodeMap.put(2,"brown");
			colorCodeMap.put(3,"Gray");
			colorCodeMap.put(4,"Black");
			colorCodeMap.put(5,"White");
		}
		
		if(sizeCodeMap==null){
			sizeCodeMap = new HashMap();
			sizeCodeMap.put("small",50);
			sizeCodeMap.put("medium",100);
			sizeCodeMap.put("large",200);
		}
		
	}

	public Passbook createPassbook(int colorCode, String size){
		
		String requestedColor = colorCodeMap.containsKey(colorCode)?
                                        (String)colorCodeMap.get(colorCode):
                                         (String)colorCodeMap.get(5);
		int requestedPageSize = sizeCodeMap.containsKey(size)
                                        ?(int)sizeCodeMap.get(size)
                                        :(int)sizeCodeMap.get("small");
		Passbook pbook = new Passbook(requestedColor,requestedPageSize);
		
		return pbook;
		
	}
}

Banker.java

public class Banker {

	public Banker() {
		// TODO Auto-generated constructor stub
	}

}

FactoryPatternMain.java

import java.util.Scanner;

public class FactoryPatternMain {

	public FactoryPatternMain() {
		// TODO Auto-generated constructor stub
	}

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		Scanner inputStream = new Scanner(System.in);
		
		PassbookFactory pbFactory = new PassbookFactory();
		
		System.out.println("enter color code (options : 1,2,3,4,5) :");
		int colorCode = inputStream.nextInt();
		System.out.println("enter passbook size (options : small, medium, large)");
		String passbookSize = inputStream.next().trim();
		
		Passbook passbookGranted = pbFactory.createPassbook(colorCode, passbookSize);
		
		System.out.println("You have been provided passbook which has color ::"+ passbookGranted.getColor()+", with pageSize::"+passbookGranted.getPageSize());
			
		
	}

}

Output