Java OOP Quiz: Inheritance, Polymorphism, Abstraction & More

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Questions and Answers

Match the following Java concepts with their descriptions:

Multidimensional Array (2D) = Data stored in row and column based index Constructors = Block of code similar to a method Inheritance = Creating new classes built upon existing classes Types of Java constructors = Default constructor and Parameterized constructor

Match the following rules for creating Java constructors with their descriptions:

Constructor name must be the same as its class name = Naming requirement for constructors A Constructor must have no explicit return type = Return type specification for constructors A Java constructor cannot be abstract, static, final, and synchronized = Restrictions on constructor modifiers Why we use inheritance in java? = Reasons for utilizing inheritance in Java

Match the following types of Java constructors with their characteristics:

Default constructor = Constructor with no arguments Parameterized constructor = Constructor with parameters specified during object creation Parent class = Class from which another class inherits properties Child class = Class that inherits properties from another class

Match the following inheritance types with their definitions:

Multilevel Inheritance = Class having more than one parent class at different levels Method Overriding = Feature of OOP where a subclass provides a specific implementation of a method that is already provided by its parent class Code Reusability = Ability to reuse code in different parts of a program Inheritances = Plural term for the concept of creating new classes based on existing ones Signup and view all the answers

What is the purpose of a constructor in Java?

To initialize the state of an object Signup and view all the answers

Which of the following is NOT a valid rule for creating a constructor in Java?

A constructor can be declared as <code>static</code> Signup and view all the answers

In the context of inheritance, what is the purpose of method overriding?

To provide a different implementation for a method inherited from a parent class Signup and view all the answers

What type of inheritance is described by the following statement: 'A class having more than one parent class but at different levels'?

Multilevel inheritance Signup and view all the answers

Which of the following is a valid reason for using inheritance in Java?

For method overriding and code reusability Signup and view all the answers

A Java constructor must have an explicit return type.

False Signup and view all the answers

Inheritance in Java allows creating new classes based on existing classes.

True Signup and view all the answers

Parameterized constructors in Java have default values if parameters are not provided.

False Signup and view all the answers

Multilevel Inheritance in Java refers to a class having more than one parent class at the same level.

False Signup and view all the answers

Java constructors can be declared as static.

False Signup and view all the answers

What are the rules for creating a Java constructor?

<ol> <li>Constructor name must be the same as its class name. 2. A constructor must have no explicit return type.</li> </ol> Signup and view all the answers

How is inheritance defined in Java and why is it used?

Inheritance in Java allows creating new classes that are built upon existing classes. It is used for Method Overriding and Code Reusability. Signup and view all the answers

What are the types of Java constructors?

The types of Java constructors are Default constructor and Parameterized constructor. Signup and view all the answers

What is Multilevel Inheritance in Java?

Multilevel Inheritance in Java refers to a class having more than one parent class but at different levels. Signup and view all the answers

When is a Java constructor called?

A Java constructor is called every time an object is created using the new() keyword. Signup and view all the answers

Study Notes

Object-Oriented Programming (OOP) in Java

OOP is a programming style that increases program flexibility and maintainability.
It allows for easy reuse of objects in other programs and manages software complexity.
OOP concepts in Java include:
- Class
- Object
- Abstraction
- Inheritance
- Polymorphism
- Encapsulation/Data Hiding

Classes and Objects

A class is a collection of objects and is a logical entity.
A class can contain:
- Fields
- Methods
- Constructors
- Blocks
- Nested classes
An object is an instance of a class and has three characteristics:
- State (represents the value of an object)
- Behavior (represents the functionality of an object)
- Identity (implemented via a unique ID)
Object definitions:
- A real-world entity
- A runtime entity
- An instance of a class

Methods in Java

A method is a collection of statements that perform a specific task and return a result to the caller.
Reasons to use methods:
- To perform a specific task
- To return a result to the caller
Types of Java methods:
- Standard Library Methods (built-in methods, e.g. print(), println(), round(), sqrt())
- User-defined Methods (defined inside a class, per requirement)

Arrays in Java

An array is used to store a collection of variables of the same type.
Array advantages:
- Code optimization
- Random access
Array disadvantages:
- Size limit (fixed size, does not grow at runtime)
Types of arrays in Java:
- Single Dimensional Array
- Multidimensional Array
Syntax to declare an array in Java:
- dataType[] arr;
- dataType []arr;
- dataType arr[];
Creating arrays:
- dataType[] arr = new dataType[arraySize];
- dataType[] arr = {value0, value1, ..., valuek};

Jump Statements in Java

Java supports three jump statements:
- Break (terminates the execution of the nearest looping statement or switch statement)
- Continue (pushes the next repetition of the loop to take place, hopping any code between itself and the conditional expression that controls the loop)
- Return (transfers control from one method to the method that called it)

Constructors in Java

A constructor is a block of code similar to a method.
When is a constructor called?
- Every time an object is created using the new () keyword.
Rules for creating a Java constructor:
- Constructor name must be the same as its class name.
- A constructor must have no explicit return type.
- A Java constructor cannot be abstract, static, final, and synchronized.
Types of Java constructors:
- Default constructor
- Parameterized constructor

Inheritance in Java

Inheritance is used to create new classes that build upon existing classes.
There are two classes:
- Parent class
- Child class
Why use inheritance in Java?
- For method overriding
- For code reusability
Inheritance is further classified into four types:
- Multilevel Inheritance (a class having more than one parent class but at different levels)

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Description

Test your knowledge on Object-oriented programming (OOP) concepts such as class, object, Inheritance, Encapsulation, Abstraction, Polymorphism, Encapsulation/Data Hiding, and Inheritance. Learn about the benefits of OOP and whether Java is considered a Pure object Oriented language.