Object Oriented Programming – Nadeesha Thilakarathne

Blueprint of a Smart Phone

HTC

Microsoft

Samsung

Apple

Operating System Model Price Battery Life

Sending SMS Voice Calling Video Calling Taking Pictures Listen to Music

Attributes of a Phone

Functions of a Mobile Phone

Galaxy S6 edge

Lumia 535

Desire 820 LTE

Main Features of Object Oriented Programming

Encapsulation

Polymorphism

Inheritance

Abstraction

Encapsulation

A black box is a device, system or object which can be viewed in terms of its inputs and outputs (or transfer characteristics), without any knowledge of its internal workings. Its implementation is "opaque“(පාරාන්ධ) (black).

Encapsulation • Providing access to an object only through its messages, while keeping

the details private is called encapsulation“.• Encapsulation is important because parts of software must

sometimes be changed or re-used.

Encapsulation

Data

Methods

Change

Access

Encapsulated

get()/set()

Use get Method

Inheritance• Inheritance is useful way to reuse code when classes share an is-

a relationship.• More specifically, if two or more classes share common behaviors

because one is a more general type of the other.• This suggests that the more specific type can "inherit" those

behaviors from the more general type.

Inheritance

Inheritance

Multiple inheritance is not supported in java through class(possible with interfaces)

InheritancePhone

HTC phone Microsoft phone Samsung phone

Inheritance • Super Class

Inheritance • Sub Class 01

Inheritance • Sub Class 02

Inheritance • Sub Class 03

Polymorphism

One Name Many Forms

With polymorphism, the same method or property can perform different actions depending on the run-time type of the instance that invokes it.

PolymorphismAs a Phone

As a Camera

As a MP3 Player

Phone

Polymorphism

Polymorphism

Compile Time(Static) Run Time(Dynamic)

Static Polymorphism(Static Binding)

• Compile time polymorphism/ Method overloading• Method overloading means there are several methods present in a

class having the • same name but • different types/order/number of parameters.

• The compiler does not consider return type when differentiating methods, so you cannot declare two methods with the same signature even if they have a different return type.

Static Polymorphism(Static Binding)

Static Polymorphism(Static Binding)

Dynamic Polymorphism(Dynamic Binding)• Run-time polymorphism is achieved by method overriding.• Method overriding allows us to have methods in the base and

derived classes with the same name and the same parameters.

Dynamic Polymorphism(Dynamic Binding)• By runtime polymorphism, we can point to any derived class from

the object of the base class at runtime that shows the ability of runtime binding.• Through the reference variable of a base class, the determination of

the method to be called is based on the object being referred to by reference variable.

Dynamic Polymorphism(Dynamic Binding)

Abstraction • Abstraction is a process of hiding the implementation details from the user.

• Only the functionality will be provided to the user. In other words user will have the information on what the object does instead of how it does it.

Abstract Class Abstract Method

Abstract Class • Abstract classes may or may not contain abstract methods • But, if a class have at least one abstract method, then the class must be declared

abstract.• Abstract class cannot be instantiated.• To use an abstract class you have to inherit it from another class, provide

implementations to the abstract methods inside the class.• If you inherit an abstract class you have to provide implementations to all the

abstract methods in it.

Abstract Class

Abstract Methods• Abstract keyword is used to declare the method as abstract.• You have to place the abstract keyword before the method name in the method

declaration.• An abstract method contains a method signature, but no method body.• Instead of curly braces an abstract method will have a semicolon ( ; ) at the end.

Inheriting the Abstract Class

Conclusion• An object is an instance of a class.• Encapsulation provides the security that keeps data and methods safe from

inadvertent( න�ාසැලකිල්නලන් සිදු ව�) changes.• Inheritance is parent-child relationship of class which is mainly used for code

reusability.• Polymorphism definition is that Poly means many and morphos means forms.• Using abstraction one can simulate real world objects.• Abstraction provides advantage of code reuse• Abstraction enables program open for extension( විස්තාරණය )

References• http://www.umsl.edu/~sauterv/analysis/488_f01_papers/quillin.htm• http://www.codeproject.com/Articles/602141/Polymorphism-in-NET• http://www.sitepoint.com/quick-guide-to-polymorphism-in-java/• http://www.tutorialspoint.com/java/java_abstraction.htm• http://tutorials.jenkov.com/java/abstract-classes.html• http://

www.w3resource.com/java-tutorial/java-object-oriented-programming.php• http://www.javatpoint.com/java-tutorial

Your Valuable Feedback is

always welcome…. Nadeesha