Programming Paradigms: OOP, Functional, Procedural

• Object-oriented Programming (OOP) is one of three programming paradigms, along with Procedural and Functional Programming.
• A programming paradigm structures and organizes code.
• The term "paradigm" is synonymous with "pattern."

Procedural Programming

• Languages include Basic, C, C++, and Pascal.
• Operations are executed sequentially.
• It uses and defines variables to hold data.
• Procedures are grouped logical units based on operations.
• Procedures are functions, modules, subroutines, and methods that Java programmers use.

Functional Programming

• Languages include Erlang, Scala, Haskell, and Elm.
• Focuses on declarations and expressions rather than statement execution.
• Functional programming intends to write clear code.
• Flow-control statements like 'for', 'while', 'break', 'continue', and 'goto' are avoided.
• Functions are the main units of this paradigm.

Object-Oriented Programming (OOP)

• It extends procedural programming.
• Objects, representing real-world models, are the building blocks.
• OOP involves creating classes (blueprints), objects (instances), and applications to manipulate those objects.
• Java, Python, VB.NET, and C# support this paradigm.

Procedural vs. Object-Oriented Programming Naming Conventions

• Variables in procedural become objects in OOP.
• User-defined data types in procedural become classes.
• Structured members become instance variables.
• Functions become methods.
• Function calls turn into message passing.

Procedural vs. Object-Oriented Programming Differences

• Procedural programming emphasizes procedures over data, while OOP emphasizes data.
• Data securitization is not a feature of Procedural programming, while data is considered secure in OOP.
• Procedural programming uses a top-down approach, and OOP employs a bottom-up approach.
• Procedural programming doesn't model real-world entities, but OOP does.
• Procedural programming decomposes programs into functions or procedures, where OOP decomposes them into objects.

Advantages of OOP

• Code is modularized using classes and objects.
• Code duplication is reduced, and reusability is increased through linking code and shared objects.
• Data security is ensured by encapsulating data with functions.
• Program complexity is reduced via inheritance.
• Creation and implementation is faster.

OOP Concepts

Class

• A group or collection of objects sharing common properties.
• It serves as the basic unit of programming.
• A class definition describes the attributes and actions of its objects.
• An attribute serves as a property of the object.

Object

• A specific and concrete instance of a class.
• This identifiable entity has characteristics and behavior.
• Features are called data members and operations called function members.

Method

• A self-contained block of code performs actions similar to a procedure in Procedural Programming.

Relating Classes, Methods, and Objects

• Automobile (class) has make/model/year/color (objects) and can move forward/backward and check gas status (methods).
• Dog (class) has breed/name/age/vaccine (objects) and can walk/eat/recognize names (methods).
• Object's class helps understand its characteristics; for example, a friend purchasing an automobile ensures it has a model name (object).

Data Abstraction

• Essential details of an entity are included, excluding background details.
• This hidden information is abstracted data.

Data Encapsulation

• This is wrapping data and functions into a class.
• It performs data hiding.

Inheritance

• This enables classes to share attributes and methods with more specific features.
• A base/parent/superclass is the class that other classes inherit properties from.
• A derived/child/subclass is the class inheriting properties from another.

Polymorphism

• "Poly" means many; "morph" means forms.
• Languages can interpret the same word or symbol correctly in various ways.

Operator Loading

• This allows operators to perform tasks differently based on the instance.

Function Overloading

• Two or more functions have the same name, but different return types or argument numbers.

Method Details

• It's a program module with statements to carry out a task, which can be called many times.
• public is an access modifier that allows any class to use it.
• static indicates a method can be used without object instantiation.
• void shows that method returns no data.
• return type describes the data type sent back to calling method.
• Method Name can be any legal identifier for classes and variables.
• Parentheses contains sent data to the method.

Method Body

• It contains implementation and statements that do the work of the method.

Fully Qualified Identifier

• Contains the complete name that includes the class is.
• It includes the class name, a dot, and the method name.

Advantages of Creating a Separate Method

• Makes main() shorter and clearer by using method calls for complex statements.
• Improves readability with well-named methods that clarify intent.
• Enhances reusability, allowing methods to be used across applications needing specific actions.

Class Header

• Has 3 parts: an optional accessor specifier, the keyword class, and a legal identifier, starting with a capital letter.

Java Class Types

• Those from which objects cannot be instantiated, such as programs with the main() methods.
• Those from which objects are created.
• With OOP a class can be created to run as an application to instantiate objects and do both.

Methods

• Accessor methods or getters retrieve values.
• Mutator methods or setters (typically prefixed with "set") set/change field values.
• Data fields are the data components inside a class (declared variables outside any method). static data fields occur once per class vs. non-static ones which happen once per object.

Constructor

• This is a special method that creates and initializes an object.