Java Inheritance | Java Inheritance Program Example | Java Inheritance Tutorial | Simplilearn

Summary

The video tutorial explains inheritance in Java using multiple examples and classes. It starts with basic concepts of superclasses and subclasses to demonstrate single inheritance. Then it covers multi-level inheritance by extending classes in a chain and hierarchical inheritance with one superclass and multiple subclasses. Real-world mobile company examples are used to show how classes inherit properties and methods from their parent classes. The examples employ getters, setters and constructors to manipulate inherited variables and output details. The summary concludes that various inheritance mechanisms allow code reuse and reduce duplication in Java OOP.

Takeaways

• 😀 Inheritance is when one class inherits properties and attributes from another class
• 👨‍💻 The types of inheritance in Java: single, multi-level, and hierarchical
• 🔀 In single inheritance, one class inherits from one other class
• ⏩ In multi-level inheritance, features trickle down from parent to child to grandchild classes
• 🌳 Hierarchical inheritance is when multiple child classes inherit from one parent class
• 📝 Use the 'extends' keyword to establish an inheritance link between classes
• 🎯 Inheritance promotes code reuse by allowing derived classes to reuse base class code
• ⚙️ The subclass can override or extend the functionality of the superclass
• 😎 Getter and setter methods allow controlled access to class variables
• 📈 Inheritance is useful in large programs when you need to manipulate many classes

Q & A

What is inheritance in Java?

Inheritance in Java is a mechanism where one class acquires the properties and behaviors of another class. The class that inherits properties is called subclass and the class whose properties are inherited is called superclass.

What are the different types of inheritance supported by Java?

The three main types of inheritance supported by Java are: 1) Single inheritance - one class inherits from one superclass 2) Multi-level inheritance - inheritance over multiple levels 3) Hierarchical inheritance - multiple subclasses inheriting from one superclass

How does single level inheritance work in Java?

In single level inheritance, one class inherits directly from one superclass. For example, class B inherits from class A. So class B can access all public and protected variables and methods of class A.

What is multi-level inheritance in Java?

In multi-level inheritance, a derived class inherits from a base class and that derived class also acts as a base class to another derived class. For example, Class C inherits from Class B, and Class B inherits from Class A. So Class C can access variables and methods of both Class A and B.

Explain hierarchical inheritance in Java.

In hierarchical inheritance, one base class has multiple subclasses inheriting from it. For example, Class A is a base class and Class B, Class C, Class D are subclasses derived from Class A. So Class B, C and D inherit the properties and behaviors of Class A.

What is the use of 'extends' keyword in Java?

The extends keyword is used by a subclass to inherit properties and behaviors from a superclass in Java. When a class extends another class using extends keyword, it can access all the non-private variables and methods of the superclass.

How can a subclass access the variables and methods of a superclass in Java?

A subclass can directly access the public and protected variables and methods of a superclass. For private variables, the subclass needs to use getter and setter methods defined in the superclass to access them.

Why is inheritance used in Java?

Inheritance is used in Java for code reuse and to establish is-a relationship between classes. It helps to reduce duplication of code as common properties and behaviors can be defined in a superclass and shared with subclasses.

What cannot be inherited in Java?

In Java, constructors and private members of a superclass cannot be inherited by subclasses. The subclasses can access private members only through methods of the superclass.

Can a class extend multiple classes in Java?

No, Java does not support multiple inheritance of classes. A class can extend only one parent class using extends keyword. However, it can implement multiple interfaces.

Outlines

00:00

📝 Introduction to inheritance in Java

The paragraph introduces the concept of inheritance in Java. It explains that inheritance allows a class to inherit properties and attributes from another class. It provides an example with a superclass 'mobiles' having variables like cost, color and ram, and subclasses 'samsung', 'xiaomi' and 'nokia' inheriting those variables.

05:01

😎 Explaining types of inheritance

The paragraph explains different types of inheritance in Java - single, multi-level and hierarchical. It provides examples for each type. Single inheritance is when one class inherits from another. Multi-level is when a derived class inherits from base class and that derived class serves as base class for another. Hierarchical is when one base class is inherited by multiple derived classes.

10:01

💻 Java code demonstration of inheritance types

The paragraph shows Java code to demonstrate the different inheritance types - single, multi-level and hierarchical. It creates classes like 'mobiles', 'android', 'samsung', 'nokia', 'xiaomi' to show single, multi-level and hierarchical inheritance in action by extending classes and accessing inherited fields.

Keywords

💡Inheritance

Inheritance refers to when one class acquires the properties and behaviors of another class. As explained in the video, when the Mobiles class is set as a superclass, the Samsung, Xiaomi and Nokia classes can inherit its variables like cost, color and RAM. This allows code reuse and modeling of real-world relationships.

💡Subclass

A subclass is a class that inherits from another class. As mentioned in the example, Samsung, Xiaomi and Nokia are subclasses that inherit from the Mobiles superclass and the Android class.

💡Single inheritance

Single inheritance is when a subclass inherits from one superclass. As demonstrated in the code, the Samsung class inherits from the Android class through extends Android. This allows Samsung to access the androidVersion variable.

💡Multiple inheritance

Multiple inheritance is when a derived class inherits from multiple base classes. The video shows how the Android class inherits from Mobiles, and Samsung further inherits from Android. So Samsung gains access to variables in both parent classes.

💡Method overriding

Though not explicitly named in the video, method overriding occurs when subclasses provide their own implementation of methods defined in parent classes. This is seen with the use of getters and setters in the code.

💡Code reuse

A key benefit of inheritance demonstrated in the code is code reuse. The Samsung, Nokia and Xiaomi classes reuse Mobiles and Android code without needing to rewrite variables and methods.

💡Abstraction

Abstraction refers to exposing only essential details and hiding complexity. The use of inheritance in the video abstracts lower-level details of features like cost, color etc into the parent Mobiles class.

💡Encapsulation

By making variables and methods private and accessing them through getters/setters, encapsulation is achieved. This is applied in the code to control access to class state.

💡Polymorphism

Polymorphism allows subclasses to define their own versions of methods. This is used with getters and setters overridden in subclasses inheriting the Mobiles class.

💡Hierarchical inheritance

Hierarchical inheritance is when multiple subclasses inherit from the same superclass. This is demonstrated through Samsung, Nokia and Xiaomi all inheriting capabilities from the Android class.

Highlights

Inheritance is when one class inherits properties and attributes from another class

Types of inheritance in Java: single, multi-level, and hierarchical

Single inheritance - one class inherits from another class

Multilevel inheritance - derived class inherits from base class and derived class acts as base class to other class

Hierarchical inheritance - one class serves as base class and two or more classes serve as derived classes

Using Java code to demonstrate single inheritance between Mobile, Android and Samsung classes

Demonstrating multilevel inheritance between Mobile, Android and Samsung classes

Hierarchical inheritance shown with Mobile as base class, Android derived, and Nokia, Xiaomi, Samsung derived from Android

Single inheritance uses one base and one derived class

Multilevel inheritance shows variables inherited from base through intermediate to final derived class

Hierarchical inheritance has one base class and multiple derived classes

Inheritance avoids rewriting redundant code by extending classes

Derived classes automatically inherit variables and methods from base classes

Inheritance is very useful for large, complex programs

Video covers the concept and implementation of Java inheritance

Transcripts

hello guys this is lakshya from simple

learn and welcome to this tutorial on

java inheritance this is a part of our

java tutorial series where we will cover

everything you need to know to master

java now without wasting any time let's

move on to our topic now let's see what

we are going to learn today first we

will see what inheritance means then the

types of inheritance that are supported

by java and finally we will see real

time programs on each of the types of

inheritance now let's see what is

inheritance when one class inherits some

properties and attributes of other class

it is known as inheritance let's have a

look at an example

in this example mobiles is of superclass

that have variables like cost color and

ram the classes that inherits the

variables and methods of mobiles are

samsung xiaomi and nokia these classes

are known as subclass now let's see the

types of inheritance in java first we

have single inheritance in single

inheritance one class inherits features

from another class as you can see above

class b inherits all properties of class

a this is a simple concept of

inheritance next we have multi-level

inheritance a derived class inherits

from base class and derived class also

act as a base class to other class

sounds complicated right now see this

example class b is derived from class a

then class c is derived from class b

because of this class c contains

properties of both class a and b this is

very effective when you go for

inheritance in big programs and lastly

we have hierarchical inheritance in this

one class serves as base class and two

or more classes serves as derived class

as you can see above class b class d and

class c have a single base class a

so three classes inherits properties of

single class this is called hierarchical

inheritance now to understand these all

concepts better let's use java code

so now let's create a new project

next

next and i'm gonna name it as

inheritance

so we have our main program here

so i'll just create a new class

new java class and for now let me just

name it as mobiles

so what are the features in mobiles to

start with

the cost of the mobile

the color of the mobile

and what can we do it as or ram of the

mobile

i am making it as string because i'm

gonna write gb as well so that's why

string

and now let's use getters and setters

for this

select all

and okay

so we have our first class mobiles here

so our first type of inheritance was

single inheritance so i'll create one

more class

and i'm gonna name it as android

and i'll make android as extends okay

i'll leave it for now

so this mobile class we are going to use

afterwards for now i'll use only android

so

let me make it as string

android

version

and for this i'm gonna go for getter and

setter

so what is single level inheritance one

class inherits from another class so

i'll create one more program or i'll

create a one more class and i'm gonna

name it as

samsung because samsung is an android

phone and as well as it comes under

mobiles so now i'm gonna extend it to

android

extends android so no need of writing

anything inside it as soon as i write

extends android i can use all the

variables right now i have only android

version as the variable

so now let's go to main program

and i'm right samsung s is equal to new

samsung

so i just created an object of it

so now if i use s dot i'll get android

version so i'll set android version as

android

pie

and now to show it

i'm gonna give it as

samsung

android version

and here s dot

get android version

so now i have android class and a

samsung class and i extended android

class to the samsung so samsung can use

all the variables here and i can even

set the variables here so if i execute

it

and here you go you can see samsung

android version that's android pie

so without even declaring even a single

variable or method here in samsung i use

the variable of android and i did this

so this is called as single level

inheritance so next i'm gonna move it

for multi-level inheritance so what is

multi-level one class is derived from

next and this class is derived from here

so i have three classes right now so i'm

gonna put android

extends

mobile

so now android can use all the variables

of mobiles i can use cost color or ram

and even samsung that extends android

can use all the variables from mobile

so if i put variables for it

s dot see i can get color cost or ram so

i'm gonna go for set color

i'm gonna give it as black

and next

s dot

set cost cost i'm gonna give it as 30

000 let it be dollar or rupees

and the last one s dot

ram

i'm gonna give it as 4 gb

so now if i print

i'll just delete all this

so now i can print them one by one so

let's just do that

so i'm gonna give it a samsung mobile

details

and then

cost

s dot get cost

next i'm gonna give it as color

plus s dot color

sorry s dot get color

and next last one i'm gonna give it as

ram

plus s dot get ram

so now you can see i have not declared

any variable inside samsung but i

inherited all the variables from here

mobiles and android so all the variables

from mobiles are here and as per android

if i put

android version

s dot get

android version

so now if i execute it i'll get all the

values and as a result i'll get

everything that i gave as the value

so now let's just execute it

so instead of cost i should put color

so as you can see i have the cost of

samsung mobile color and ram and even

android version so all these variables i

gave in mobile and android version i

gave in android class

but nothing in samsung class so this is

how multi-level inheritance works so now

let's move on to the third topic that

was hierarchical inheritance so what is

hierarchical inheritance in that three

classes or two classes have a single

base class so i'm gonna create two more

classes that derives android so now

let's create them

next i'm gonna name it as nokia

and the last one

xiaomi

so these are real time examples three

mobiles we have three different

companies and all uses android and they

all come under mobiles

so now in everything i'm gonna write

extends android

so this is the final version of

inheritance that we have and this is

very simple to understand but it might

get complicated when we use big programs

or very large programs for some project

so now i have nothing inside class nokia

or xiaomi or samsung i'm gonna use all

the variables that come from android and

mobiles as android extends mobiles so

this is the concept like i have three

classes three mobile companies that

comes under android and we can use them

to manipulate the variables and assign

values to the variables so i already

have everything from samsung

so first let's create objects for all

these classes

nokia n is equal to new nokia

and xiaomi x is equal to new

xiaomi

so now i'm going to assign variables to

their values so now let's start with

nokia

dot

set color

let's give it as red

n dot set cost i'm gonna give it as 40

000

again doesn't matter because it's a

normal program so it doesn't matter

whether it's dollar or rupees

so next n dot

set ram

ram 4 gb

and lastly n dot set android version

android marshmallow

so and in the end i'm gonna give x dot

let's just copy paste it

so it will be lot easier for

me to code or for you to code

so here x dot

and color i'm gonna give it as

silver

rate 50 000 ram 6 gb

and android let's give it some old

so

get cat

so now we have set all the values to the

variables so now let's print them as

well so again i'm gonna copy paste all

those details

instead of samsung nokia

here it gets n

n

instead of s

and now again copy paste

now xiaomi

x dot

x dot

x

and finally x so with this i have

completed the program i can show you all

the

values that i gave in the starting let's

just revise it

so in mobiles i gave all the variables

cost color and ram android i extended

from mobiles and i gave one more

variable as android version

nokia xiaomi and samsung i gave nothing

but i only extended android

so now let's execute it

so we have successfully executed our

program let's have a look at it

so here samsung mobile details in the

starting color cost

after that

nokia mobiles and in the end xiaomi

mobile and everything that we gave as

the value are here so with this we have

completed our program i hope you

understood what inheritance is so i'll

just revise it one more time so in

single level inheritance i used only

samsung android and mobiles and samsung

i derived from android and i used only

android version in the starting next i

used multi-level inheritance in that i

used mobile's android and samsung

with the use of mobile variables

i use samsung and i printed the values

of color cost ram and android version as

samsung

in the next that is hierarchical

inheritance i used nokia xiaomi and

samsung

so i hope you understood what the

concept of inheritance means so this

brings us to the end of this video we

learnt everything about java inheritance

and all its types using java code i hope

you like the video thank you for

watching and stay tuned for more from

simply learn

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