Introduction to Object-Oriented Programming

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Questions and Answers

What is a fundamental feature of object-oriented programming that allows different classes to share common attributes and methods?

Encapsulation

Inheritance (correct)

Abstraction

Polymorphism

Which of the following statements best describes a class in object-oriented programming?

A class is a blueprint for creating objects. (correct)

A class is a method that performs actions on data.

A class is a process that involves multiple behaviors.

A class is a variable that holds data about an object.

In object-oriented programming, what is the term used for the unique data specific to an instance of a class?

Methods

Instance Variables (correct)

Attributes

Class

What concept in object-oriented programming refers to the specific actions or functions associated with an object?

Methods Signup and view all the answers

Which object-oriented concept encapsulates the idea of hiding the internal state and requiring all interaction to be performed through methods?

Encapsulation Signup and view all the answers

What term describes the mechanism of sending data to an object and requesting it to perform a specific method?

Message Passing Signup and view all the answers

Which of the following is NOT a characteristic of an object in object-oriented programming?

Template Signup and view all the answers

Which of the following best differentiates object-oriented programming from procedural programming?

Object-oriented programming focuses on creating objects, while procedural programming focuses on actions. Signup and view all the answers

What keyword is used to create a new object in Java?

new Signup and view all the answers

Which constructor would be invoked if a Book object is created with no parameters?

Book() Signup and view all the answers

In the UML representation, what does the '-' symbol before a variable indicate?

private access Signup and view all the answers

In the given C# constructor for the Book class, what message is printed when a Book object is created with the title 'Java'?

the title is: Java Signup and view all the answers

What does the 'bark()' method in the Dog class return?

void Signup and view all the answers

What is the purpose of a constructor in a class?

to initialize object attributes Signup and view all the answers

How many constructors are defined in the Book class sample provided?

2 Signup and view all the answers

If a class named 'Car' has a method called 'stop()', what type of access is indicated by the '+' symbol?

public access Signup and view all the answers

What type of variable exists within a class but outside any method and is accessible in all methods of the class?

Instance variables Signup and view all the answers

What is the main characteristic of constructors in a class?

They must have the same name as the class. Signup and view all the answers

Which of the following is true regarding case sensitivity in C#?

Identifiers are case sensitive, meaning 'Hello' and 'hello' are different. Signup and view all the answers

What is the correct syntax for a default constructor in a class named ClassName?

class ClassName { ClassName() { } } Signup and view all the answers

In which order should the three steps for creating an object from a class be correctly followed?

Declaration, Initialization, Invocation Signup and view all the answers

What is the required starting case for method names in C#?

Lower Case Signup and view all the answers

Which option describes a local variable in C#?

It is defined inside methods and destroyed when the method ends. Signup and view all the answers

Which of the following best defines class variables?

They are static variables declared outside any method within a class. Signup and view all the answers

Study Notes

Object-Oriented Programming Introduction

Object-oriented programming (OOP) focuses on creating objects that contain both data and methods.
Procedural programming focuses on writing procedures or methods to manipulate data.

Object-Oriented Languages

OOP languages commonly support concepts like Polymorphism, Inheritance, Encapsulation, Abstraction, Classes, Objects, Instances, Methods, and Message Passing.

Objects and Classes

An object has states (characteristics) and behaviors (actions).
A class is a template or blueprint defining the behavior and state of its objects.
Objects are instances of a class.
- Each object inherits all variables and methods from its class.
Example: A "Car" class can have objects like "Mercedes," "Volvo," and "Toyota."

Objects in Programming Languages

Real-world objects (cars, dogs, humans) have states (characteristics) and behaviors (actions).
Software objects mirror this with states stored in fields and behaviors shown via methods.
Method calls operate on the object's internal state and are the communication means between objects.

States and Behaviors

The state of an object is its properties (data). Alternative terms: instance variables, fields, properties, variables, members.
Behaviors are the actions an object can perform (methods, functions, procedures).

Variable Types in a Class

Local variables: Declared and initialized within a method; destroyed when the method ends.
Instance variables: Belong to a specific object; initialized when the object is created. Accessed from within any method of the class containing it.
Class variables: Belong to the class itself (not a specific object), declared with the "static" keyword. Accessed directly via the class name rather than an object instance.

Constructors

Constructors are special methods called when a new object is created from a class.
They initialize the new object's state.
Each class has at least one constructor.
Constructors have the same name as the class. A class can have multiple constructors.

Basic Syntax

OOP code uses proper casing for identifiers. This means that Java, C# naming conventions are case-sensitive.
Variables - camel case (use lowercase for the first word)
Class Names - upper camel (use uppercase for every first character of each word)
Method names - camel case (start with a lowercase letter).

Creating an Object

Create an Object from a class in three steps:
- Declare a variable of the class type
- Instantiate the object using the 'new' keyword
- Initialize the object by calling a constructor.
Use the format [Object type] [variable name] = new [Constructor]();

UML

UML (Unified Modeling Language) diagrams visually represent classes and their relationships.
A UML diagram of a class can show the states (data) and behaviors (actions) of that class graphically.
Use symbols like - for private access modifiers, and + for public access.

Classes (Sample Code)

Classes are blueprints for creating objects.
A class definition essentially creates all variables, actions, and properties for an object.
A class can include instance variables, local variables, class variables, and methods

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Description

This quiz explores the fundamentals of object-oriented programming (OOP), including its core principles such as classes, objects, inheritance, and polymorphism. You'll learn how OOP differs from procedural programming and how it models real-world entities through software objects. Test your understanding of key concepts and terminology in OOP.