Java is called Object Oriented Programming where as C called Procedure oriented programming. There are always confusion and enquiry. It is always a question why did new paradigm evolve when there was already existing paradigm which did not have much hassles.
There are few questions which always click to mind. Few are as following
ü What is Object Oriented Programming?
ü What are the fundamental concepts/Features of OOP?
ü What is Object Based Programming?
ü What is structured programming?
ü What are the features of structured programming?
ü Compare OOP and SP?
These are the few questions that have been troubling me for past few years. Now when I am four years senior in IT then it feels best to start looking for answers and understand them.
What is Object Oriented Programming?
Object Oriented Programming known as OOP is a programming paradigm which relies on data. It is a paradigm which represents data and its use. So basically an object is a representation of data structure which consist fields and methods, which provides a way a interaction between each other.
OOP concepts were mainly introduced for maintainability of code. Earlier people were having function oriented approach, which was becoming difficult to maintain in the long term. To get rid of this tedious process orientation moved to data and communication of data, which was introduced in OOP. OOP is a collection of interacting object having communicating facilities between objects. The technology focuses on data rather than processes/procedure/functions.
Simula was the first language which introduced the concepts of OOP, it was followed by LISP. Well known language to us is JAVA.
public class DemoClass {
private int test = 0;
public int getTest() {
return test;
}
public void setTest(int test) {
this.test = test;
}
Here class DemoClass has a variable which has an integer as field who is deterministic factor to define the state of the object of the class (We will discuss private and public modifier later). getTest method will provide the state of the variable whereas setTest method will change the existing state of the test variable.
This class uses oops fundamental where it is designed around data instead of procedures/functions.
class InteractWithDemo{
DemoClass testDemo = new DemoClass();
public void useTestDemo(){
testDemo.setTest(10);
testDemo.getTest();
}
PS: Please ignore the syntax if you are not aware.
InteractWithDemo class works as interacting class with the class created above. It creates an object of DemoClass and change the state of the DemoClass's object. This is the way objects interact with each other.
What are the fundamental concepts and Features of OOP?
Foundation of every entity is kept on fundamental concepts and it is appreciated on the basis of features. OOP also have few fundamental concepts and few others important and fascinating features.
Following are the fundamental concepts and Features of OOP
ü Object
ü Class
ü Instance
ü Method
ü Interface
ü Package
ü Message Passing
ü Abstraction
ü Encapsulation
ü Polymorphism
ü Inheritance
These are the fundamental concepts along with that features of OOPS. Let’s discuss them in details further.
Object
Object is any entity who has characteristics, behaviours and state. In our day to day we see lots of object. Every human in itself is an object. How? Each individual has few characteristics which can be used to uniquely identify him. E.g. A person has name, DOB, parents name which are used to uniquely identity him. The same guy will have some habits. His state can be his age, marital status, job status, property balance and many more things. So a human being is an object. Similarly we have software concepts.
There are few advantage listed to have objects:
ü Modularity
ü Information Hiding
ü Code Re-Use
ü Pluggability and Debugging Use Case.
Class
Class is the blue print of the Object. Class is to hold the state and the behaviour of the entity. In the example given above, here to define a state of a human being following is the information that may suffice to define a unique person
- Name
- DateOfBirth
- Father's name
- Mothers' Name
These 4 attribute can tell the characteristics of the human along with that we can more variable to define the state and accordingly there can be few methods which define characteristics.
Instance
Instance is an occurrence or copy of an object. Multiple instances, of a class share, same set of attributes whereas value of the attributes may differ for each instance.
Methods
Method is a subroutine which is either associated to a class or to an instance of object. Method is a sequence of the statement to perform an action on the instances of objects or classes. Method may have inputs which are either processed or used to modify the state of the object. Few methods return the required datatype.
In case of OOP, methods provide the mechanism for accessing and manipulating the encapsulated data of the object.
In OOP these are type of methods:
- Static methods - Mainly associated with the class.
- Instance Methods - Affiliated with the instance of the class i.e. object.
- Constructor - Cannot be called explicitly, in general these methods are used for initialization purpose.
- Abstract Methods - These methods do not body defined for it (Implementation of the method is not given) i.e. sequence of instructions are defined by some other class.
- Destructor - Cannot be called explicitly, in general these methods are used for object destroy purpose.
Interface
Best example to define interfaces will be a TV Set with a remote functionality. E.g. let’s say Videocon has different types of TV, where display type, screen size are different but company wants to create a generic remote for all. So Generic Remote is an interface to interact with TV object of various types of TV classes.
Here interface remote will be implemented by each TV class to perform actions guided by user.
Interface defines the behaviour to interact with outside the world.
interface Remote{
void increaseVolume();
void reduceVolume();
void nextChennal();
void previousChannel();
void changeChennalTo(int);
}
As defined above interface remote has defined five methods. Implementations of these methods have not been provided in the interface. Now when a class implements an interface it will implement all methods. Interfaces form a contract between the class and the outside world, whereas this contract is enforced at build time by the compiler.
Package
Package is similar to the folders in windows, which are used to manage the data better and efficient. Packages are the namespace which provide better overview and understanding of the classes and their utilization. It is recommended, while coding related objects should belong to the same package.
Message passing
Message passing is a method of communication where sender sends messages to one or more than one recipients. These forms of message are method invocation, signal and packets.
In case of OOP invocating a method from object, class or other object is called message passing. The order in which message have been passed in their reversal order method responses are received by the sender.
Abstraction
An "abstraction" (noun) is a concept that acts as super-categorical noun for all subordinate concepts, and connects any related concepts as a
group,
field, or
category.
In OOP abstraction is used to provide bare minimum information at the user level. The information which matters the user most is provided. Abstraction asks to make sure to provide minimal information. As user does not internals of the class, object, database and design it is not even altered with the changes of inside the objects.
The best thing of abstract is that this decouples the user of the object and its implementation. So now object is easy to understand and maintain also. As if there is any change in the process of some operation. You just need to change the inner details of a method, which have no impact on the client of class.
Encapsulation
Encapsulation is data hiding or reducing the access to others. Here it is made sure that every field of the class should not be accessible from the outside world. They should be taken care by methods and their accessibility should not go beyond the boundaries of the class. Encapsulation is a tool which provides the way to implement abstraction for a class.
Inheritance
Inheritance is well known terminology used in programming fundamentals. Inheritance is child’s rights on his father’s property. i.e. anything that belongs to father will belong to child until unless father explicitly mentions his wishes. Same inheritance is applied in Java, if class is child of a class it means it will be able to use all the members other than private members.
Usage of inheritance is very important in reusability of the code, which reduces the efforts of rewriting the same code again.
Polymorphism
It is a paradigm where values of two different data type are handled by uniform interface. In other way 2 methods or fields name can co exist with different set of parameters?
Polymorphism is better known as providing similar functionality to different set of parameters. In java achieving polymorphism is possible in 2 ways. Overriding and overloading which will be analyzed in the further discussions.
Disclaimer: All the material here is the result of research and understanding of other material. If there is some content which is either incorrect or inappropriate to the context of the article I am always open for discussion.
