OOP Pillars

Question 1

__________ in Java is a mechanism in which one object acquires all the properties and behaviors of a parent object

Answer 1

Inheritance

Question 2

The idea behind inheritance in Java is that you can create new classes that are built upon existing _______.

Answer 2

classes

Question 3

When you inherit from an existing class, you can reuse methods and fields of the parent class. Moreover, you can add new methods and fields in your current class also.

True or False

Answer 3

True

Question 4

___________ means “many forms”, and it occurs when we have many classes that are related to each other by inheritance.

Answer 4

Polymorphism

Question 5

___________ lets us inherit attributes and methods from another class. ___________ uses those methods to perform different tasks.

Answer 5

Inheritance lets us inherit attributes and methods from another class. Polymorphism uses those methods to perform different tasks.

Question 6

Inheritance represents the ___ relationship which is also known as a ___________ relationship.

Answer 6

Inheritance represents the IS-A relationship which is also known as a parent-child relationship.

Question 7

What are the Advantages of Inheritance?

Answer 7

• For Method Overriding (so runtime polymorphism can be achieved).
• For Code Reusability.

Question 8

____ is a group of objects which have common properties. It is a template or blueprint from which objects are created.

Answer 8

class

Question 9

________ is a class which inherits the other class. It is also called a derived class, extended class, or child class.

Answer 9

subclass

Question 10

__________ is the class from where a subclass inherits the features. It is also called a base class or a _____ ____.

Answer 10

Superclass is the class from where a subclass inherits the features. It is also called a base class or a parent class.

Question 11

________ is a mechanism which facilitates you to reuse the fields and methods of the existing class when you create a new class. You can use the same fields and methods already defined in the previous class.

Answer 11

reusability

Question 12

The _______ keyword indicates that you are making a new class that derives from an existing class. The meaning of “_______” is to increase the functionality.

class Subclass-name extends Superclass-name

{

//methods and fields added here

}

Answer 12

extends

Question 13

What are the three types of inheritance in java?

Answer 13

single, multilevel and hierarchical

Question 14

In java programming, ________ and ______ inheritince is supported through interface only.

Answer 14

In java programming, multiple and hybrid inheritance is supported through interface only.

Question 15

Is multiple inheritance supported by Java?

Answer 15

No

Question 16

The most common use of ___________ in OOP occurs when a parent class reference is used to refer to a child class object.

Answer 16

polymorphism

Question 17

Any Java object that can pass more than one IS-A test is considered to be __________

Answer 17

polymorphic

Question 18

If a class has multiple methods having same name but different in parameters, it is known as ______ _________

Answer 18

Method Overloading

Question 19

If we have to perform only one operation, having same name of the methods _________ the ___________ of the program.

Answer 19

If we have to perform only one operation, having same name of the methods increases the readability of the program.

Question 20

What are the two ways to overload the method in java?

Answer 20

• By changing number of arguments
• By changing the data type

class Adder{

static int add(int a, int b){return a+b;} // 2 arguments

static int add(int a, int b, int c){return a+b+c;} //3 arguments

}

Question 21

Method overloading is not possible by changing the return type of the method.

True or False

Answer 21

True

Question 22

If subclass (child class) has the same method as declared in the parent class, it is known as _____ ________ in Java

Answer 22

method overriding

Question 23

______ overriding is used to provide the specific implementation of a method which is already provided by its superclass.

Answer 23

​

• Method overriding is used to provide the specific implementation of a method which is already provided by its superclass.

Question 24

_______ overriding is used for runtime polymorphism

Answer 24

Method overriding is used for runtime polymorphism

Question 25

What are the 3 rules required for method overriding to work?

Answer 25

• The method must have the same name as in the parent class
• The method must have the same parameter as in the parent class.
• There must be an IS-A relationship (inheritance).

Question 26

Can a static method be overridden?

Answer 26

No, a static method cannot be overridden.

Question 27

____________ in Java is a mechanism of wrapping the data (variables) and code acting on the data (methods) together as a single unit.

Answer 27

Encapsulation

Question 28

In __________, the variables of a class will be hidden from other classes, and can be accessed only through the methods of their current class.

Answer 28

encapsulation

Question 29

We can create a fully encapsulated class in Java by making all the data members of the class _______.

Answer 29

private

Question 30

Once the data member of class have been made private we can use _____ and _____ methods to ___ and ___ data

Answer 30

Once the data member of class have been made private we can use getter and setter methods to get and set data

Question 31

The ____ ____ class is the example of a fully encapsulated class.

Answer 31

Java Bean

Question 32

What are the 4 access modifiers?

Answer 32

• private
• default
• protected
• public

Question 33

What is the accessibility scope of each access modifier?

private

default

protected

public

Answer 33

Question 34

__________ is a process of hiding the implementation details and showing only functionality to the user.

Answer 34

Abstraction

example: sending SMS where you type the text and send the message. You don’t know the internal processing about the message delivery.

Within Parent class

public abstract int calculateSalary();

Child Class

You define what calculateSalary() function does in the child class

Question 35

________ lets you focus on what the object does instead of how it does it.

Answer 35

Abstraction

Question 36

______________ is the process of extracting shared characteristics from two or more classes, and combining them into a generalized superclass. Shared characteristics can be attributes, associations, or methods.

Answer 36

Generalization

IE. taking two similar classes that have shared attributes, and then creating a superclass and moving the shared attributes into and then extend those attributes to the subclasses. So the two original classes are now subclasses of the superclass that now contains the once shared characterson

Question 37

___________ means creating new subclasses from an existing class. If it turns out that certain attributes, associations, or methods only apply to some of the objects of the class, a subclass can be created.

Answer 37

Specialization

ie. When it comes to Specialization, if there is a property that is only applicable to a specific subclass, such as Degree of Hazardousness, that property is placed in the class Piece of Cargo where-in this class also has all the properties of the Freight class with the concept of Generalization.

Question 38

’

Any Java object that can pass more than one ____ test is considered to be polymorphic.

Answer 38

IS-A