Classes and Objects

Question 1

A high-level, powerful programming language that
uses the Object-Oriented Programming (OOP)
approach.

Answer 1

Java

Question 2

A programming style that models real-world entities as “objects.”

Answer 2

Object-Oriented Programming (OOP)

Question 3

Objects have: (mention 2)

Answer 3

Data (fields): Information or attributes.
Behavior (methods): Actions or functions.

Question 4

Objects have:
Data (fields): ______________
Behavior (methods): _____________

Answer 4

Data: Information or attributes.
Behavior: Actions or functions.

Question 5

Programs are written as step-by-step instructions or
functions.

Answer 5

Traditional Programming (Procedural)

Question 6

What is a Class?

Answer 6

A class is like a blueprint or template for creating
objects.

Question 7

Mention two Variables in a Class:

Answer 7

Instance Variables
Class Variables

Question 8

What type of variable is this in a class?
* Declared inside a class but outside any method.
* Non-static and unique to each object.

Answer 8

Instance variables

Question 9

What type of variable is this in a class?
* Declared with the static keyword.
* Shared across all objects of the class.

Answer 9

Class variables

Question 10

An ________ is a real-world entity created from a class.

Answer 10

object

Question 11

If a ______ is a blueprint, an object is the actual
product made from that blueprint.

Answer 11

class

Question 12

The process of creating an object
from a class.

Answer 12

Instantiation

Question 13

___________ are the characteristics or properties of
an object.

Answer 13

Attributes

Question 14

Attributes are also called ________ or ________
variables.

Answer 14

fields or instance
variables.

Question 15

Do attributes belong to a class? True or false

Answer 15

True

Question 16

Each object has its own copy of class
variables. True or false

Answer 16

False
Each object has its own copy of instance
variables not class variables.

Question 17

_________ variables are specific to an object
and can only be accessed within that
object.

Answer 17

Instance

Question 18

Java reserves ________ for the object based on the class blueprint.

Answer 18

memory

Question 19

The name of the class.

Answer 19

ClassName

Question 20

The name of the object (instance).

Answer 20

objectName

Question 21

This keyword allocates memory for the object.

Answer 21

new

Question 22

Calls the class constructor to initialize the object.

Answer 22

ClassName()

Question 23

We can create ___________ attributes (which belong to individual objects) and ________ attributes (which belong to the class itself)

Answer 23

non-static , static

Question 24

To access the attributes of a class, we create an ________ and use _____________.

Answer 24

object , dot notation (.)

Question 25

A special method used to initialize objects when they are created.

Answer 25

Constructor

Question 26

A constructor is a special method used to _________ objects when they are created.

Answer 26

initialize

Question 27

It has the same name as the class and runs automatically during object instantiation.

Answer 27

Constructor

Question 28

What are the 2 types of Constructors?

Answer 28

1.Default Constructor (No Parameters) 2. Constructor with Parameters

Question 29

Assigns default values to object attributes.

Answer 29

Default Constructor

Question 30

Allows assigning custom values when creating an object.

Answer 30

Constructor with Parameters

Question 31

Default Constructor has list of parameters. True or false?

Answer 31

**False** Default constructor has no parameter.

Question 32

What are the types of access modifiers?

Answer 32

● **Public**: Accessible everywhere. ● **Private**: Accessible within the class only. ● **Protected**: Accessible within the package and subclasses. ● **Default**: Accessible within the package.

Question 33

● __________: Accessible everywhere. ● __________: Accessible within the class only. ● __________: Accessible within the package and subclasses. ● __________: Accessible within the package.

Answer 33

● Public: Accessible everywhere. ● Private: Accessible within the class only. ● Protected: Accessible within the package and subclasses. ● Default: Accessible within the package.

Question 34

Multiple methods with the same name but different parameters.

Answer 34

Method Overloading

Question 35

Wrapping data and methods into a single unit.

Answer 35

Encapsulation

Question 36

One class acquires properties and methods of another class.

Answer 36

Inheritance

Question 37

Refers to parent class members.

Answer 37

super Keyword

Question 38

Ability to take multiple forms.

Answer 38

Polymorphism

Question 39

Two types of Polymorphism:

Answer 39

Compile-time (Method Overloading) Runtime (Method Overriding)

Question 40

* Hiding implementation details and showing functionality. * Achieved through Abstract Classes and Interfaces.

Answer 40

Abstraction

Question 41

* Cannot be instantiated. * Can have abstract and non-abstract methods.

Answer 41

Abstract class

Question 42

* It is a collection of abstract methods. * It also Implements multiple inheritance.

Answer 42

Interface

Question 43

final Keyword: ● _________: Constant value. ● _________: Cannot be overridden. ● _________: Cannot be inherited.

Answer 43

● **Final Variable:** Constant value. ● **Final Method**: Cannot be overridden. ● **Final Class**: Cannot be inherited.

Question 44

Superclass of all classes in Java.

Answer 44

Object Class

Question 45

. Type Casting ● _________: Subclass to Superclass. ● _________: Superclass to Subclass.

Answer 45

● **Upcasting**: Subclass to Superclass. ● **Downcasting**: Superclass to Subclass

Question 46

instanceof Operator: * Checks if an object is an instance of a class. (visualize the syntax to answer)

Answer 46

if (obj instanceof ClassName) {}

Question 47

Group of related classes and interfaces

Answer 47

Packages

Question 48

Used to include packages.

Answer 48

import keyword

Question 49

Accessing Package Members - Fully Qualified Name or ________________.

Answer 49

Import Statement

Question 50

Mechanism to handle runtime errors.

Answer 50

Exception Handling

Question 51

Automatic memory management.

Answer 51

Garbage Collection

Question 52

Convert primitive data types into objects.

Answer 52

Wrapper Classes

Question 53

Immutable sequence of characters.

Answer 53

String Class

Question 54

Collection of similar type elements.

Answer 54

Arrays

Question 55

Resizable array implementation.

Answer 55

Array list Class

Question 56

Stores key-value pairs.

Answer 56

HashMap Class

Question 57

Reading and writing files.

Answer 57

File handling

Question 58

Concurrent execution of two or more threads.

Answer 58

Multithreading

Question 59

Converting an object into byte stream.

Answer 59

Serialization

Question 60

OOP enhances code _________, ____________, ___________.

Answer 60

reusability, security, and modularity

Question 61

Method overloading allows a class to have ___________ with the same ________ but different ____________.

Answer 61

multiple methods, same name but different parameter list

Question 62

Retrieves the value of a private variable.

Answer 62

Accessor (Gate)

Question 63

Modifies the value of a private variable with validation.

Answer 63

Mutator (Setter)

Question 64

Variables or methods can only be accessed within the same class.

Answer 64

Private Access