This Presentation is about java design patterns. I have covered some OOPs concepts as well: Polymorphism, Interface, Inheritance, abstraction etc. And the Main Topic Covers: Factory Design Patterns,Observer Design Patterns,Proxy Design Patterns,Adapter Design Patterns,MVC Design Patterns etc

2. What is Java?
Programming Language
Fast
Secure
Reliable

3. What is Java?
Programming Language
Fast
Secure
Reliable

4. Some Facts about JAVA:
Developed by JAMES GOSLING at SUN MICROSYSTEMS
Related to two languages C and C++
HOW ?
JAVA derives its Syntax from C and,
Many concepts based on OOPs were influenced by C++
Initially JAVA was named as “Oak” But was renamed by “JAVA” in 1995
3977 classes

5. The Way JavaWorks :
Objective :Write an Application and make it run on whether
devices your friends have.

6. The JAVA BUZZWORDS :
Simple
Secure
Portable
Dynamic
Distributed
Object-oriented
Robust(Consistent)
Multithreaded
Architecture neutral
High Performance

7. Major OOP Principles :
Abstraction
Encapsulation
Inheritance
Polymorphism

8. Abstraction:
 Manages Complexity(Generalization)
 Hierarchal Classification
 Makes Java more Understandable

9. Encapsulation:
Binds Code and data Together
Keeps it safe from outside interference and Misuse
It works through Classes. A
AB
C
CD
C is accessible with in this Block

10. Inheritance :
Process of acquiring the properties of another object
In absence of inheritance, each object needs to define all characteristics

11. Polymorphism :
An Ability of an object to acquire more than one form
For example:
public interface Vegetarian{ }
public class Animal{ }
public class Deer extends Animal implements Vegetarian{ }
A Deer IS-A Animal
A Deer IS-A Vegetarian
A Deer IS-A Deer
A Deer IS-A Object

12. Interface :
 It is an Collection of Abstract Methods
 It can contain any no. of methods
 How do it do this???
HOW ?

13. Lets Design Some
Patterns
General solution to programmers problems faced while designing software
Increase the Code Maintainability
GOF: Erich Gamma, Richard helm, Ralph Johnsons and John vlissides
Helps in Reusing the codes
Time saving and Cost reduction

14. Types Of Patterns
Creational Pattern:
Way to create Objects while hiding the Creational Logic
Structural Pattern:
Concerns class and object composition
Behavioral pattern:
Referred to communication between objects
J2EE:
Presentation tier.

15. Classification Of Patterns
Creational pattern:
1. Factory Pattern
2. Singleton Pattern
3. Abstract Factory Pattern
4. Builder Pattern
5. Prototype Pattern
Structural Patterns:
1. Adapter Pattern
2. Composite Pattern
3. Proxy Pattern
4. Flyweight Pattern
5. Façade Pattern
6. Bridge Pattern
7. Decorator Pattern
Behavioral Pattern:
1. Template Method Pattern
2. Mediator Pattern
3. Chain of Responsibility Pattern
4. Observer Pattern
5. Strategy Pattern
6. Command Pattern
7. State Pattern
8. Visitor Pattern
9. Iterator Pattern
10. Memento Pattern

16. Factory Pattern

17. Factory Pattern
Comes Under the creational Pattern
Create object without Exposing the Creational Logic
used to instantiate an object from one among a set of classes based on a logic
Assume that you have a set of classes which extends a common super
class or interface. Now you will create a concrete class with a method which
accepts one or more arguments.This method is our factory method.

18. Factory Pattern
Super Class
SubClass 3Sub Class 2Sub Class 1
Factory Super ClassLogic

19. Factory Pattern

20. Adapter Pattern
Allows you to use two Incompatible Interfaces to work together
Used when the client expects a(target) interface
Adapter Class allows the use of available Interface and the target
 interface
Any class can work together as long as the Adapter solves the issue
that All classes must implements every method defined by the
shared interface

21. Adapter Pattern
Client
Enemy Attacker
<Interface>
Fire weapon():void
Drive Forward():void
Assign driver():void
Enemy Robot Adapter
Fire weapon():void
Drive Forward():void
Assign driver():void
Enemy Robot
Smash with hands():void
walk Forward():void
React to human():void
Enemy Robot
Enemy Attacker
(Target)
Enemy Robot Adapter
(Adaptor)
Enemy Robot
(Adaptee)

22. Adapter Pattern

23. Observer Pattern
In observer design pattern multiple observer objects registers with
a subject for change notification.When the state of subject changes,
it notifies the observers. Objects that listen or watch for change are
called observers and the object that is being watched for is called
subject.
Pattern involved is also called as publish-subscribe pattern. Model
view controller (MVC) architecture’s core uses the observer design
pattern.

24. Observer Pattern
Subject provides interface for observers to register and unregister
themselves with the subject.
Subject knows who its subscribers are.
Multiple observers can subscribe for notifications.
Subject publishes the notifications.
Subject just sends the notification saying the state has changed. It does
not pass any state information.
Once the notification is received from subject, observers call the subject
and get data that is changed.

25. Observer Pattern
Consider an excel sheet, data is shown to the user in different
views. Generally data is shown in grid cells and as required
different graphs, charts can be created for same data. Underlying
data is same and when that data (subject) state changes all the
different view are updated.
 When multiple
objects depend on
state of one object
and all these multiple
objects should be in
sync with the state of
this one object then
observer design
pattern is the right
choice to apply.
When?

26. Observer Pattern
Let us take a blog and
subscriber example for
observer design pattern
sample implementation.
Assume that there is a blog
and users register to that
blog for update.When a new
article is posted in the blog,
it will send update to the
registered users saying a
new article is posted.Then
the user will access the blog
and read the new article
posted. In this example, blog
is the subject and user is the
observer.

27. Proxy Design Pattern
Proxy means ‘in place of’. In attendance roll call, we give proxy for
our friends in college right? ‘Representing’ or ‘in place of’ or ‘on
behalf of’ are literal meanings of proxy and that directly explains
proxy design pattern.

28. Proxy Design Pattern
Remote Proxy – Represents an object locally which belongs to a
different address space.Think of an ATM implementation, it will
hold proxy objects for bank information that exists in the remote
server.
Virtual Proxy – In place of a complex or heavy object use a
skeleton representation.
Protection Proxy –working on a MNC? If so, you might be well
aware of the proxy server that provides you internet. Saying more
than provides, the right word is censors internet.
Smart Reference – Just we keep a link/reference to the real object
a kind of pointer.

29. Proxy Design Pattern
Provide a class which will limit access to another class
You may do this for Security reasons, because an Object is intensive
to Create, or is accessed from a remote location.

30. Proxy Design Pattern
Client
GetATMState
<interface>
+getATMState(): ATMState
+getCashINMachine():int
ATM Proxy
+getATMState(): ATMState
+getCashINMachine():int
ATM Machine
+getATMState(): ATMState
+getCashINMachine():int

31. MVC Design Pattern
Completely Separates the Calculation and Interface from each other
Model: Data and Model Used to Work with it
View:The Interface
Controller: Coordinates interactions between the view and Model
My Favorite One!!

32. Rahul Malhotra
rahulbtibusiness@gmail.com
+91-74041-37709
www.facebook.com/btiworld14