Object-Oriented Programming (OOP)

• OOPS (Object-Oriented Programming) focuses on real-world entities like cars and ATMs.

Procedural vs. OOPS

• Procedural programming divides programs into functions, while OOPS divides them into objects.
• OOPS provides data hiding, giving importance to data, while procedural programming doesn't inherently hide data.
• Overloading and inheritance are possible in OOPS but not in procedural programming.
• OOPS promotes code reusability, which is not a feature of procedural programming.
• Examples of procedural languages are Pascal, C, and FORTRAN.
• Examples of OOPS languages are Java, C#, Python, and C++.

Objects & Classes

• An object is defined by properties (or state) and behavior (or function).
• Dogs have properties like age, color, and breed and behaviors like barking, sleeping, and eating.
• Cars have properties like color, type, brand, and weight and behaviors like applying the brake, driving, and increasing speed.
• A class serves as a blueprint or skeleton for creating objects.
• Multiple objects can be created from a single class.
• The "class" keyword is used to create a class.

Data Abstraction

• Data abstraction hides the internal implementation and only shows essential functionality to the user.
• It can be achieved through interfaces and abstract classes.
• The brake pedal in a car is an example of abstraction.
• Using a cellphone is another example of abstraction.
• Data abstraction enhances security and confidentiality.
• In an example, an interface Car specifies methods like applyBrake(), incSpeed(), and handbrake().
• A class carImp that implements Car can have a different implementation inside the methods.

Data Encapsulation

• Data encapsulation bundles data and the code that works on that data into a single unit.
• It is also known as data hiding.
• Encapsulation involves declaring class variables as private.
• Public getters and setters are provided to modify and view these variables.
• Encapsulation leads to loosely coupled code.
• Encapsulation offers better access control and security.

Inheritance

• Inheritance allows a class to inherit properties from a parent class.
• Inheritance allows inheriting both functions and variables from parent class.
• The "extends" keyword or interfaces can be used to achieve inheritance.
• Multiple inheritance is when one class inherits from multiple classes.
• Polymorphism can be achieved using inheritance.
• Types of inheritance include single, multilevel, hierarchical, and multiple inheritance.
• Multilevel inheritance represents inheritance across multiple layers of classes.
• Hierarchical inheritance occurs when multiple classes inherit from a single class.
• Multiple inheritance is not fully supported by Java due to the diamond problem.

Polymorphism

• Polymorphism means "many forms".
• The same method can behave differently in different situations.
• A person can act as a father, husband, or employee.
• Water can exist as a liquid, solid, or gas.
• Polymorphism types include compile-time (static polymorphism/method overloading).
• Polymorphism types include run-time (dynamic polymorphism/method overriding).

Method Overloading

• Method overloading practice involves creating methods with the same name but different parameters.
• The method is called based on the parameters.

Relationships

• "Is-a" relationships are achieved through inheritance.
• Example: a DOG is an animal.
• "Is-a" relationship is shown by inheritance.
• "Has-a" relationships is when an object is used in another class.
• The relationship can be one-to-one, one-to-many, or many-to-many.
• Association is a relationship between two different objects.
• Aggregation allows both objects to survive individually.
• Composition means ending one object will end another object.