#CoreJava/ObjectOrientedProgramming

Programming Language

• Script - Reserved Keyword
• Grammar - Syntax

Programming Language for machine understanding

Machine Advantages:

• Accuracy
• Speed

Machine Disadvantages:

• Memory - We have use to proper utilize the memory

Procedural vs Object Oriented Programming

• C is a procedural-oriented programming language.
• C++ and Java are object-oriented programming languages.
• In procedural programming, processes are followed step by step.
• Changing or implementing new features in a procedural approach can be difficult because it may require altering the entire process.
• Object-oriented programming is easier to modify compared to the procedural method due to its modular structure.

What is OOPs?

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• OOPs stands for Object-Oriented Programming.
• It’s a way of organizing code around objects, which represent real-world things.
• Key concepts include classes, objects, inheritance, polymorphism, and encapsulation.
• OOP helps make code reusable, modular, and easier to manage.
• Common OOP languages include Java, C++, and Python.

OOPs Features

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The key features of OOPs (Object-Oriented Programming) are:

1. Encapsulation: Bundling data and methods together, and restricting direct access to some of the object’s components.
2. Inheritance: One class can inherit properties and behaviors from another class.
3. Polymorphism: Objects can take many forms, allowing methods to be used in different ways.
4. Abstraction: Hiding complex details and showing only the essential features.

Object

• Object - Real Time Entity
• Object - Structure (State) and Usage (Behaviour)
• State (Data) + Behaviour (Methods) = Class
• Object is instance of Class
• Object memory create at runtime
• Objects are dynamic memory size
• That object will have its state and access to all of the behavior defined by the class.
• An object without class is not possible.
• A class without object is possible.

Identity - Hashcode (Hashcode is generated using a hashing algorithm)
Instance - எடுத்துக்காட்டு
Instantiation means object creation.
Attributes - State

Both tangible and intangible objects are possible.
An example of a tangible object is the laptop.
An example of an intangible object is the banking system.
Tangible - உறுதியான (உணரமுடியும் )
Intangible - உணரமுடியாத

Creation of Object Syntax

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class_name object_name = new class_name();

Explanation: we are using the new keyword to create the object of the class class_name, we can also observe, how the constructor of the class is been called using the new keyword.

new - allocates memory for object inside of the class. It is dynamic memory size.
class_name() - இந்த Brackets இல்லாம object create செய்யமுடியாது. இந்த Brackets constructor உடன் தொடர்புடயவை.

new class_name() --> Object
object_name --> Object Reference

Example:

MobileShop samsungMobile = new MobileShop();

What is Object?

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• Object is Real Time Entity
• It is a combination of State(Variables) and Behaviour(Methods)
• Object is instance of a class
• Object memory create at runtime and dynamic memory size.
• For example, a car object might have properties like color and speed, and behaviors like accelerator or Brake apply.

What are the Characteristics of Object?

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An object has three characteristics:

• State: The data or values the object holds (e.g., variables).
• Behavior: The actions or functions the object can perform (e.g., methods).
• Identity: A unique reference that distinguishes one object from another.

How many types to create an objects in java?

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There are several ways of creating an objects in java, they are:

1. new keyword

2. newInstance() method of Class class
3. newInstance() method of Constructor class
4. clone() method
5. Deserialization in Java
6. Factory Method Pattern

Is it possible to run a Java program without creating an object? How does it work if all methods are static?

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• Yes, it is possible can run without creating an object if all methods are static.
• Example

public class Example {
    // Static method
    static void displayMessage() {
        System.out.println("Hello, World!");
    }

    // Main method (also static)
    public static void main(String[] args) {
        // Call static method without creating an object
        displayMessage();
    }
}

What is Class?

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• A class is a blueprint or template in Object-Oriented Programming that defines the properties (variables) and behaviors (methods) of objects.
• A Class is a collection of similar types of objects.
• It is a user-defined data type and doesn't occupy any memory.

Syntax of Class

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class ClassName{
	//attributes (Objects)
	//methods
}

Explanation:

• class is a reserved keyword in java
• Class names should be written in PascalCase.

Member Functions
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The functions are written inside a class are known as member functions.

Instance variables
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Variables that are declared within the scope of the class.

Give any 5 Classes in java

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• Concrete Class - (Normal Class)
• Final Class
• Abstract Class
• Wrapper Class
• Static Class

Structure of a Java Project

Follow this order:

• Project (Drive)

• Package (Folder)

• Class (File)

  Package Naming Convention:

  • Use the reverse of your internet domain. For example: com.demo.firstproject
  • Use only lowercase letters.

  Class Name Naming Convention:

  • Don't start with a number.
  • Don't use spaces.
  • Alphanumeric names are allowed. Example: Project1
  • Avoid special characters except for underscores.
  • Use PascalCase for class names.

  Correct classname examples:

  • MyFirstProject
  • My_First_Project
  • My1Project