Principles of Object Oriented Programming (OOP)

This article aims to explain the principles of Object-Oriented Programming in Java, using simple way to make it easier  to understand the fundamentals. 

Table of Contents:

Understanding the Foundations of Object-Oriented Programming

1.1 What is Object-Oriented Programming?

1.2 Why is OOP Important?

The Four Key Principles of OOP

2.1 Encapsulation: Bundling Data and Methods

2.2 Inheritance: Reusing and Extending Code

2.3 Polymorphism: Adapting to Different Situations

2.4 Abstraction: Simplifying Complex Systems

Applying OOP Principles in Java

3.1 Classes and Objects: Building Blocks of OOP in Java

3.2 Encapsulation in Java: Access Modifiers and Getters/Setters

3.3 Inheritance in Java: Extending Classes and Overriding Methods

3.4 Polymorphism in Java: Method Overloading and Method Overriding

3.5 Abstraction in Java: Abstract Classes and Interfaces

Advantages of Object-Oriented Programming in Java

4.1 Code Reusability and Modularity

4.2 Improved Maintainability and Scalability

4.3 Enhanced Collaboration and Teamwork

1. Understanding the Foundations of Object-Oriented Programming

1.1 What is Object-Oriented Programming?

Object-Oriented Programming (OOP) is a programming paradigm that focuses on modeling real-world entities as objects, which are instances of classes. In OOP, objects encapsulate both data (attributes) and methods (functions) related to a specific entity, providing a clear structure for building complex systems.

1.2 Why is OOP Important?

OOP offers several benefits over other programming paradigms. It promotes code reusability, as objects can be easily reused in different parts of the program. OOP also enhances code organization, making it easier to maintain and modify. Moreover, OOP fosters collaboration among developers, as they can work on different classes and objects simultaneously.

2. The Four Key Principles of OOP

2.1 Encapsulation: Bundling Data and Methods

Encapsulation is the practice of bundling data and methods together within a class. In Java, this is achieved by using classes and objects. By encapsulating data, we ensure its integrity and hide the internal implementation details from other parts of the program. This improves security and allows for easy modifications without affecting other parts of the code.

2.2 Inheritance: Reusing and Extending Code

Inheritance is a powerful feature in Java that allows new classes (derived classes) to inherit properties and behaviors from existing classes (base classes). By reusing code, developers can save time and effort. Inheritance establishes hierarchical relationships between classes, enabling them to inherit fields and methods from a superclass. This promotes code reuse and reduces redundancy.

2.3 Polymorphism: Adapting to Different Situations

Polymorphism allows objects of different classes to be treated as objects of a common superclass. In Java, polymorphism is achieved through method overloading and method overriding. Method overloading enables the creation of multiple methods with the same name but different parameter lists, while method overriding allows a subclass to provide its own implementation of a method defined in the superclass. Polymorphism enhances code flexibility and extensibility.

2.4 Abstraction: Simplifying Complex Systems

Abstraction involves simplifying complex systems by defining abstract classes and interfaces. Abstract classes provide a blueprint for subclasses, defining common attributes and methods. Interfaces, on the other hand, define a contract that implementing classes must adhere to. Abstraction allows developers to focus on the essential features of an object while hiding unnecessary details, making code more manageable and understandable.

3. Applying OOP Principles in Java

3.1 Classes and Objects: Building Blocks of OOP in Java

In Java, classes are used to create objects, which are instances of those classes. A class defines the properties (attributes) and behaviors (methods) that objects of that class can have. Objects are created using the new keyword, and they interact with each other by invoking methods and accessing attributes.

3.2 Encapsulation in Java: Access Modifiers and Getters/Setters

Encapsulation in Java is achieved through access modifiers and getter/setter methods. Access modifiers (public, private, protected, and default) control the visibility of attributes and methods. Getters and setters allow controlled access to private attributes, ensuring data integrity and providing a standardized way of modifying and retrieving data.

3.3 Inheritance in Java: Extending Classes and Overriding Methods

In Java, inheritance is accomplished by using the extends keyword. A subclass can extend a single superclass, inheriting its attributes and methods. Subclasses can also override inherited methods to provide their own implementation. This enables code reuse and promotes the creation of hierarchical relationships.

3.4 Polymorphism in Java: Method Overloading and Method Overriding

Polymorphism in Java is achieved through method overloading and method overriding. Method overloading allows the creation of multiple methods with the same name but different parameter lists. The appropriate method is selected based on the arguments provided during the method call. Method overriding, on the other hand, occurs when a subclass provides its own implementation of a method defined in the superclass. This allows different objects to respond differently to the same method call.

3.5 Abstraction in Java: Abstract Classes and Interfaces

Abstraction in Java involves defining abstract classes and interfaces. An abstract class serves as a blueprint for subclasses, providing common attributes and methods. It cannot be instantiated itself. Interfaces define a contract that implementing classes must adhere to, specifying a set of methods that must be implemented. Abstraction allows developers to focus on the essential features of an object and provides a clear structure for building complex systems.

4. Advantages of Object-Oriented Programming in Java

4.1 Code Reusability and Modularity

OOP promotes code reusability by allowing objects to be reused in different parts of the program. This saves time and effort in development. Additionally, OOP encourages modularity, as code is organized into classes and objects, making it easier to understand, maintain, and modify.

4.2 Improved Maintainability and Scalability

With OOP, code maintenance becomes easier. The encapsulation and abstraction principles ensure that changes to one part of the codebase do not affect other parts. This simplifies debugging and updates. OOP also enables scalability, as new classes and objects can be added without affecting the existing codebase.

4.3 Enhanced Collaboration and Teamwork

OOP promotes collaboration among developers working on a project. Classes and objects can be assigned to different team members, allowing them to work independently on their assigned components. This modular approach enhances teamwork and facilitates parallel development.

Frequently Asked Questions (FAQs)

7.1 What is the main difference between a class and an object in Java?

In Java, a class is a blueprint or template that defines the attributes and behaviors of objects. It represents a general concept. On the other hand, an object is an instance of a class. It is created using the new keyword and represents a specific occurrence of that class. Objects have their own set of values for attributes and can invoke methods defined in the class.

7.2 How does encapsulation ensure data security in Java?

Encapsulation in Java hides the internal implementation details of a class and allows controlled access to attributes and methods. By using access modifiers like private for attributes, they cannot be directly accessed from outside the class. Access is provided through getter and setter methods, which validate and control the modification of attribute values. This ensures data security and integrity.

7.3 Can multiple inheritance be achieved in Java?

Java does not support multiple inheritance, where a class can inherit from multiple classes. However, Java does support multiple interface inheritance, where a class can implement multiple interfaces. This allows a class to inherit the method signatures from multiple interfaces and provide its own implementation.

7.4 What is the significance of method overriding in Java?

Method overriding in Java allows a subclass to provide its own implementation of a method defined in the superclass. It enables the subclass to customize the behavior of inherited methods according to its specific requirements. Method overriding is essential for achieving polymorphism and dynamic method dispatch.

7.5 Are there any alternatives to Java for implementing OOP?

Yes, there are alternative programming languages that support OOP, such as C++, Python, and Ruby. These languages have their own syntax and features for implementing object-oriented principles. The choice of language depends on the specific requirements of the project and the preferences of the development team.

Thank you guys.

Java Features

Popular programming language Java is known for its ease of use and adaptability. Here are some of its major features:

• Object-oriented: Java follows the object-oriented programming (OOP) approach, which means it organizes code into objects that have properties (attributes) and behaviors (methods). This allows for modular and reusable code.

• Platform independence: Java programs can run on different operating systems and hardware platforms without any modifications. The Java Virtual Machine (JVM), which converts Java code into a format that the system on which it runs can understand, allows this.

• Automatic memory management: You don't need to manually create and deallocate memory since Java handles memory management. Writing bug-free code is made simpler by the garbage collector that automatically releases memory by deleting objects that are no longer needed.

• Robustness: Java is designed to be robust and reliable. It includes features like exception handling, which allows programmers to handle errors gracefully, preventing crashes and unexpected behavior.

• Security: Java has built-in security features that protect against unauthorized access and malicious code. The JVM enforces security measures such as sandboxing, which isolates Java programs from the underlying system, reducing the risk of security breaches.

Java features

• Rich standard library: Java comes with a vast collection of pre-built classes and methods, known as the Java Standard Library. This library provides a wide range of functionality, including input/output operations, networking, data structures, and more, saving developers time and effort.

• Multithreading: Java supports multithreading, which allows programs to execute multiple tasks concurrently. This is especially useful for applications that need to handle multiple user interactions or perform background tasks without blocking the main program.

• Portability: Java's platform independence and widespread adoption make it highly portable. Once a Java program is written, it can be run on any system that has a compatible JVM, making it easy to distribute and deploy applications.

• Scalability: Java supports scalability, which means it can handle the growing demands of an application. It provides features like thread pooling, which allows efficient utilization of system resources, and the ability to distribute workloads across multiple machines or servers.

• Community support: Java has a large and active community of developers. This means there are plenty of online resources, forums, and libraries available to help you learn and solve problems. The community also contributes to the continuous improvement of Java through updates and new libraries.

• Documentation: Java has extensive documentation, including official guides, tutorials, and API references. This documentation helps developers understand the language and its various libraries, making it easier to write clean and maintainable code.

• Robust ecosystem: Java has a vast ecosystem of third-party libraries and frameworks. These libraries cover a wide range of functionalities, such as database connectivity, user interface development, testing, and more. Leveraging these resources can speed up development and enhance the capabilities of Java applications.

These features contribute to Java's popularity and widespread use across various industries and application domains. Whether you're building small applications or large-scale systems, Java provides a solid foundation for developing reliable and robust software.

These features make Java a versatile language suitable for a wide range of applications, from desktop software to web development, mobile apps, and even large-scale enterprise systems.

Thank you guys.

Class vs Object

1. Class is a group of element having similar properties and behaviours , while Object is a  individual elements with seperate physical property and behaviour.
2. Class is BluePrint of the Objects while Object is instance of Class.
3. Class is a logical entity it contains logics where as object is physical entity it is representing  memory.
4. Without class we are unable to create object.
5. Based on single class (blue print) it is possible to create multiple objects but every object occupies memory.
6. Using blue print of house we are able to create number of houses and each house required some area/space.
7. For declaring the class we use class keyword and for creating object we need new keyword.

Ex:
Test t = new Test();

Object creation will start when jvm(java vertual machine) encounter "new" keyword. 
We can able to create object of Class in different ways. We will discuss object creation in detailed in  constructor .
Thank you guys.

What is Class ?

JAVA is object oriented technology because to represent total data in the form of object.
By using object reference variable we are calling all the methods, variables which is present in that class.

Class Main
{
......
   ......
}
Main m=new Main();

Main intention or you can say main purpose of classes in Java is to represent all real world entities in Java program in the form of classes like customer class, student class , employee class .
In simple word class is nothing but a container which contains other programing elements like variable , methods, constructor etc or you can say it is like a carry bag. So now you see how class is related with real world.
Many students find programing difficult ? Because they are missing that mapping , to map real world entities with Java programs. Every entity must have data and some behaviour or actions , to represent data of entity we have variables

Ex: int a =10;
"a" is variable of integer type holding 10 as a data.
Ex: For Student class we have data like student id , student name , student age , student class ,so for these number of data we will create variable .

Entity must have behaviour/actions like getStudentDetails , delete/update studentdetails , In Java these actions are represent in the form of methods.

Steps to create class in Java programs:

1.Declare a class by using "class" keyword.
2.Declare entity data in the form of variables.
3.Declare entity behaviours in the form of methods.
4.In main class,In main() method,create an object and reference variable for the class.
5.Access the members of the class by using reference variable.

Class Syntax:

[Access_Modifiers] class class Name[extends Super_Class][implements interface_List]
{
}

Note:-
1. Only public and <default> are allowed for the classes , private and protected are not allowed for the classes , because  access modifiers private and protected scopes are defined on the boundaries of classes so we can not apply them for the classes , rather they apply for the members of the classes
2. All the access modifiers like public,protected , default and private are allowed for the inner classes.

3. If we don’t mention the scope to the class , then  automatically the scope of the class is “default”

4. "extends" is a keyword , it can be used to specify super class in class syntax inorder to reuse the members of super class in the present subclass
5. "implements" is a java keyword , which can be used to specify one or more interface names in order to implement all the interface methods in the present class.

 
Class Elements:-
Class Test
{
1. variables ------- int a = 10;
2. methods ------- void add() {}
3. constructors------ Test() { }
4. instance blocks----- { }
5. static blocks------ static { }
}

Java codeing conventions for classes:

1. Class name start with upper case letter and every inner word starts with upper case letter.
2. This convention is also known as camel case convension.

Ex:- Student , StudentDetails etc

Now take one  example to understand clearly.

Example:

class Student
{
// Instance variables
int sid=101;
String sname=”Peter”;
String saddr=”london”;
int smarks=95;

//Instance methods
void get_Student_Details()
{
System.out.println(“****Student Details****”);
System.out.println(“Student ID:”+sid);
System.out.println(“Student name:”+sname);
System.out.println(“Student Marks :”+smarks);
System.out.println(“Student Address:”+saddr);
}
}

class Demo
{
public static void main(String[] args)
{
Student s=new Student();
s.get_Student_Details();
}
}

Output:
****Student Details****
Student ID:101
Student name:Peter
Student Marks:95
Student Address:london

Please run this example on your editor and do tell me your outputs.

On next post I will discuss on classes and objects. Thanku guys. Keep learning.

Oops introduction

Now a days every programing languages following oops methodology , so it is very important for you also to learn and understand object oriented programing(Oops). I am going to explain each and everything related to Oops by taking related examples and with proper clear cut explanations .

Any programing languages allows it's application to represent or store data in the form of objects is nothing but a object oriented programing languages.In order to set data in object we need to follow certain rule and regulations or you can say certain set of conventions,and this set of conventions is called as Oops features.Oops has seven number of features:
               1.Class
               2.Object
               3.Abstraction
               4.Polymorphism
               5.Inheritance
               6.Encapsulation
               7.Message Passing

I will discuss above features separately later on. Oops provide very good shareability and reusability and also very good abstraction and security to application .so how we achieve these features? If we follow all Oops feature correctly then we are able to create very good application like web applications , enterprise applications, standalone application, mobile applications.

In my next post I will discuss Oops features separately. Thanku guys.