Java/C3/Subclassing-and-Method-Overriding/English-timed - Revision history

Sandhya.np14 at 08:50, 19 September 2018

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Pratik kamble at 11:07, 23 November 2017

2017-11-23T11:07:54Z

Jyotisolanki at 07:05, 18 October 2017

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Sandhya.np14 at 03:14, 17 May 2017

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Sandhya.np14 at 02:50, 17 May 2017

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PoojaMoolya at 14:13, 20 February 2017

2017-02-20T14:13:47Z

PoojaMoolya: Created page with " {| border=1 | '''Time''' | '''Narration''' |- | 00:01 | Welcome to the spoken-tutorial on''' Subclassing''' and '''Method overriding.''' |..."

2016-08-12T08:57:35Z

Created page with " {| border=1 | <center>'''Time'''</center> | <center>'''Narration'''</center> |- | 00:01 | Welcome to the spoken-tutorial on''' Subclassing''' and '''Method overriding.''' |..."

New page

{| border=1
| <center>'''Time'''</center>
| <center>'''Narration'''</center>

|-
| 00:01
| Welcome to the spoken-tutorial on''' Subclassing''' and '''Method overriding.'''

|-
| 00:06
| In this tutorial we will learn about :

* '''subclassing'''
* '''extends '''keyword and
* '''method overriding'''

|-
| 00:15
|Here we are using

* '''Ubuntu''' '''Linux '''version 12.04
* '''JDK '''1.7
* '''Eclipse '''4.3.1

|-
| 00:25
|To follow this tutorial, you must have knowledge of basics of '''Java''' and '''Eclipse IDE.'''

|-
| 00:32
| If not, for relevant '''Java '''tutorials, please visit our website.

|-
| 00:37
| First of all, we will learn what '''subclassing '''is.

|-
| 00:41
| It is a way to create a new '''class''' from an existing '''class.'''

|-
| 00:46
| The new '''class''' created is '''subclass '''or''' derived class '''or''' child class.'''

|-
| 00:53
| The already existing '''class''' is called '''superclass '''or''' base class '''or''' parent class.'''

|-
| 01:00
| Now, let me show you how to create a subclass. I have already created a project named '''MyProject'''.

|-
| 01:10
| I have created a '''class ''' in it named '''Employee.'''

|-
| 01:15
| It has '''variables, name '''and '''email_address.'''

|-
| 01:19
| It also has the '''setter '''and '''getter methods '''for the '''class.'''

|-
| 01:24
| It has a '''method getDetails().''' This '''method '''returns '''name '''and''' email_address.'''

|-
| 01:31
| Now, let us come to the '''Manager class'''.

|-
| 01:35
| It has '''variables, name, email_address '''and '''department.'''

|-
| 01:40
| We can see that some '''variables''' are common to both '''Employee '''and '''Manager class.'''

|-
| 01:47
| '''name '''and''' email_address '''are present in the '''Employee class.''' We can see that its also there in '''Manager class.'''

|-
| 01:57
| Thus, '''Manager class '''can be made a '''subclass''' of '''Employee class.'''

|-
| 02:03
| For that, we have to make some changes in the '''Manager class.'''

|-
| 02:08
| After '''public class Manager, '''type '''extends Employee'''

|-
| 02:14
| We use the '''extends keyword '''to create a '''subclass '''from an existing '''class.'''

|-
| 02:21
| Remove the duplicate '''variables '''common to both the '''classes.'''

|-
| 02:26
| So, remove '''name '''and''' email_address '''from '''Manager class.'''

|-
| 02:32
| Also remove '''setter '''and '''getter methods '''of the same.

|-
| 02:37
| In the '''class Manager, '''we will have only one '''variable department.'''

|-
| 02:43
| We also have the '''setter '''and '''getter method '''for '''department.'''

|-
| 02:59
| In this way, the '''Manager class '''inherits the members of '''Employee class.'''

|-
| 02:55
| This way of extending one '''class '''from another is called '''single inheritance.'''

|-
| 03:02
| I have also created another '''class '''named '''TestEmployee.'''

|-
| 03:08
| Inside the '''main method, '''we will create the '''object '''of '''Manager class.'''

|-
| 03:14
| So inside the '''main method''', type '''Manager manager equal to new Manager parentheses

|-
| 03:23
| Next, we will call the '''setter methods '''of the '''Manager class.'''

|-
| 03:28
| So type, '''manager dot setName''' within brackets and double quotes '''Nikkita Dinesh '''

|-
| 03:38
| Then type, '''manager dot setEmail '''within brackets and double quotes '''abc at gmail dot com'''

|-
| 03:49
| Then type, '''manager dot setDepartment''' within brackets and double quotes '''Accounts'''

|-
| 03:57
| You can use any '''name, email address''' and '''department'''.

|-
| 04:02
| Now, let us call the '''getDetails() method '''using the '''Manager object.'''

|-
| 04:08
| So, type '''System.out.println '''within brackets '''manager dot getDetails '''

|-
| 04:17
| Now, let us save and run the program.

|-
| 04:21
| We can see that we get the '''output '''as ''':'''

'''Name: Nikkita Dinesh'''

'''Email: abc@gmail.com'''

|-
| 04:30
| Here, the '''object '''of the '''Manager class '''calls the '''getDetails() method.'''

|-
| 04:36
| Now, come to the '''Manager class.'''

|-
| 04:39
| We can see that there is no '''getDetails() method '''here.

|-
| 04:43
| But, we still got the output. This is because, the '''Manager class extends '''the '''Employee class.'''

|-
| 04:52
| The '''Manager class '''automatically inherits the '''variables '''and '''methods '''of '''Employee class.'''

|-
| 04:59
| So it checks in the '''parent class '''which is '''Employee.'''

|-
| 05:04
| Let us come to the '''Employee class.''' It finds the '''getDetails() method '''here.

|-
| 05:11
| Note that we have not returned the '''department.''' As a result, it did not print the '''department '''in the output.

|-
| 05:20
| Now, let us change the '''getDetails method ''' to '''private.''' Save the file.

|-
| 05:27
| We can see that we get a compilation error in the '''TestEmployee class.'''

|-
| 05:34
| It says '''The method getDetails() from the type Employee is not visible.'''

|-
| 05:40
| This means that '''getDetails() method '''cannot be accessed.

|-
| 05:45
| This is because we have declared '''getDetails() method '''as '''private.'''

|-
| 05:52
| A '''subclass''' does not inherit the '''private''' members of its '''superclass'''.

|-
| 05:58
| '''Subclass '''cannot directly access the '''private''' members of the '''superclass.'''

|-
| 06:04
| The superclass can have '''public''' or '''protected methods'''.

|-
| 06:09
| These '''methods''' can access its '''private''' fields.

|-
| 06:13
| The '''subclass''' can also access the '''private''' fields through these '''methods'''.

|-
| 06:18
| So, let us change it back to '''public.'''

|-
| 06:21
| Now, let us include the '''method getDetails '''in the '''Manager class.'''

|-
| 06:27
| This '''method '''will return '''name, email_address '''and '''department.'''

|-
| 06:33
| So type, '''public String getDetails''' parentheses.

|-
| 06:39
| Inside the '''method''', type '''return''' within brackets '''Name''' plus '''getName()''' plus '''slash n''' plus '''Email''' plus '''getEmail() '''plus '''slash n''' plus '''Manager of '''plus '''getDepartment() semicolon.''' Save the file.

|-
| 07:07
| Note that now, we have the '''method getDetails '''in both '''Manager''' and '''Employee class.'''

|-
| 07:15
| The '''name, return type '''and '''argument list '''of the''' method '''is same in both the '''classes.'''

|-
| 07:22
| A''' method '''in the '''subclass '''is said to '''override '''the '''method '''in the '''parent class '''if:

* '''name'''
* '''return type'''
* '''argument list'''

matches exactly.

|-
| 07:33
| Come back to the '''Manager class.'''

|-
| 07:36
| Before, the '''getDetails() method '''type '''@Override.'''

|-
| 07:43
| This is an '''override annotation.''' It indicates that a '''method''' is intended to '''override''' a '''method''' in '''superclass'''.

|-
| 07:53
| Now, let us see what '''annotation '''is.

|-
| 07:57
| '''Annotations:'''

* start with '''at sign''' character
* provide data about a program
* have no direct effect on the operation of the code.

|-
| 08:10
| If a '''method '''is '''annotated '''with '''@Override, compiler '''generates '''error '''if: the''' method''' does '''override''' a '''method''' declared in a '''superclass'''.

|-
| 08:23
| The '''method signature '''is different in its '''superclass.'''

|-
| 08:28
| Now, let us come back to the '''IDE.''' Come back to the '''Manager class.'''

|-
| 08:34
| The '''at sign''' character indicates the compiler that what follows is an '''annotation.'''

|-
| 08:42
| Here, it shows that the '''getDetails method '''is '''overridden.'''

|-
| 08:48
| Let us come to the '''TestEmployee class.'''

|-
| 08:51
| Save the file and run the program.

|-
| 08:55
| We get the '''output''' as follows.

'''Name: Nikkita Dinesh'''

'''Email: abc@gmail.com'''

'''Manager of Accounts'''

|-
| 09:05
| Here, the '''object '''of the '''Manager class '''calls the '''getDetails() method.'''

|-
| 09:11
| But this time, it calls the '''method''' of '''Manager class''' itself.

|-
| 09:16
| In this way, we override the '''method''' of the '''parent class '''by the '''subclass'''.

|-
| 09:23
| Let us summarize.

In this tutorial we have learnt about

* '''Subclassing''' and
* '''Method Overriding'''

|-
| 09:31
| As an '''assignment'''

Create a '''class Vehicle '''which has a method '''run '''that prints “'''The Vehicle is running.”'''

|-
| 09:40
| Also create a class '''Bike '''which has a method '''run '''that prints “'''The Bike is running safely.”'''

|-
| 09:48
| The output should be “'''The Bike is running safely.”'''

|-
| 09:52
| To know more about the Spoken Tutorial Project

* Watch the video available at the following link
* It summarizes the Spoken Tutorial project
* If you do not have good bandwidth, you can download and watch it

|-
| 10:06
|The Spoken Tutorial Project Team

* Conducts workshops using spoken tutorials
* Gives certificates for those who pass an online test
* For more details, please write to '''contact at spoken hyphen tutorial dot org'''

|-
| 10:21
|Spoken Tutorial Project is a part of the Talk to a Teacher project.

* It is supported by the National Mission on Education through ICT, MHRD, Government of India.

* More information on this Mission is available at

* http://spoken-tutorial.org/NMEICT- Intro

|-
| 10:42
| This is '''Arya Ratish '''from '''IIT Bombay '''signing off.

Thanks for joining.

|}

@@ Line 66: / Line 66: @@
 |-
 | 01:35
-| It has '''variables, name, email_address '''and '''department.'''
+| It has variables- '''name, email_address '''and '''department.'''
 |-

@@ Line 113: / Line 113: @@
 |-
-| 02:59
+| 02:49
 | In this way, the ''''Manager' class '''inherits the members of ''''Employee' class.'''

@@ Line 10: / Line 10: @@
 |-
 | 00:06
-| In this tutorial, we will learn about:
+| In this tutorial, we will learn about:  '''subclassing''' , '''extends '''keyword and  '''method overriding'''.
-* '''subclassing'''
-* '''extends '''keyword and
-* '''method overriding'''.
 |-
 | 00:15
-|Here we are using:
+|Here we are using:  '''Ubuntu Linux '''version 12.04 , '''JDK '''1.7 , '''Eclipse '''4.3.1
-* '''Ubuntu Linux '''version 12.04
-* '''JDK '''1.7
-* '''Eclipse '''4.3.1
 |-
@@ Line 172: / Line 166: @@
 |-
 | 04:21
-| We can see that we get the output as:
+| We can see that we get the output as: '''Name: Nikkita Dinesh''' ,'''Email: abc@gmail.com'''
 '''Name: Nikkita Dinesh'''
-−
 '''Email: abc@gmail.com'''
 |-
@@ Line 280: / Line 271: @@
 | 07:22
 | A''' method '''in the '''subclass '''is said to '''override '''the '''method '''in the '''parent class '''if:
-*'''name'''
+'''name''' ,'''return type''' ,'''argument list''' ,match exactly.
-−
-*'''return type'''
-−
-*'''argument list'''
 match exactly.
 |-
@@ Line 305: / Line 291: @@
 |-
 | 07:57
-| '''Annotations:'''
+| '''Annotations:'''  start with '''at (@)''' sign character , provide data about a program , have no direct effect on the operation of the code.
-* start with '''at (@)''' sign character
-* provide data about a program
-* have no direct effect on the operation of the code.
 |-
 | 08:10
-| If a '''method '''is annotated with '''@Override''', compiler generates '''error '''if:
+| If a '''method '''is annotated with '''@Override''', compiler generates '''error '''if:  the''' method''' does '''override''' a '''method''' declared in a '''superclass'''.
-* the''' method''' does '''override''' a '''method''' declared in a '''superclass'''.
 |-
 | 08:23
-|* The '''method signature '''is different in its '''superclass.'''
+| The '''method signature '''is different in its '''superclass.'''
 |-
@@ Line 341: / Line 323: @@
 |-
 | 08:55
-| We get the '''output''' as follows:
+| We get the '''output''' as follows: '''Name: Nikkita Dinesh''' ,'''Email: abc@gmail.com''' ,'''Manager of Accounts''' .
 '''Name: Nikkita Dinesh'''
-−
 '''Email: abc@gmail.com'''
-−
 '''Manager of Accounts'''
 |-
@@ Line 362: / Line 339: @@
 |-
 | 09:23
-| Let us summarize. In this tutorial, we have learnt about:
+| Let us summarize. In this tutorial, we have learnt about:'''Subclassing''' and '''Method Overriding'''.
-*'''Subclassing''' and
-*'''Method Overriding'''.
 |-
@@ Line 385: / Line 360: @@
 | 10:06
 |The Spoken Tutorial Project Team:
-*Conducts workshops using spoken tutorials
+Conducts workshops using spoken tutorials
-*Gives certificates for those who pass an online test.
+Gives certificates for those who pass an online test.
 For more details, please write to '''contact at spoken hyphen tutorial dot org'''.

@@ Line 172: / Line 172: @@
 |-
 | 04:21
-| We can see that we get the output as ''':'''
+| We can see that we get the output as:
 '''Name: Nikkita Dinesh'''
 '''Email: abc@gmail.com'''
@@ Line 266: / Line 267: @@
 |-
 |  06:39
-| Inside the '''method''', type '''return''' within brackets '''Name''' plus '''getName()''' plus '''slash n''' plus '''Email''' plus '''getEmail() '''plus '''slash n''' plus '''Manager of '''plus '''getDepartment() semicolon.'''  Save the file.
+| Inside the '''method''', type: '''return''' within brackets '''Name''' plus '''getName()''' plus '''slash n''' plus '''Email''' plus '''getEmail() '''plus '''slash n''' plus '''Manager of '''plus '''getDepartment()''' semicolon.  '''Save''' the file.
 |-
 | 07:07
-| Note that now, we have the '''method getDetails '''in both '''Manager''' and '''Employee  class.'''
+| Note that now, we have the method '''getDetails '''in both ''''Manager'''' and ''''Employee' class.'''
 |-
@@ Line 279: / Line 280: @@
 | 07:22
 | A''' method '''in the '''subclass '''is said to '''override '''the '''method '''in the '''parent class '''if:
-'''name'''
+*'''name'''
 '''return type'''
-'''argument list'''
+*'''return type'''
-matches exactly.
 |-
 | 07:33
-| Come back to the '''Manager class.'''
+| Come back to the '''Manager''' class.
 |-
 | 07:36
-| Before, the '''getDetails() method '''type '''@Override.'''
+| Before the '''getDetails() method, '''type: '''@Override.'''
 |-
@@ Line 303: / Line 306: @@
 | 07:57
 | '''Annotations:'''
-start with '''at sign''' character
+* start with '''at (@)''' sign character
-provide data about a program
+* provide data about a program
-have no direct effect on the operation of the code.
+* have no direct effect on the operation of the code.
 |-
 | 08:10
-| If a '''method '''is '''annotated '''with '''@Override, compiler '''generates '''error '''if:  the''' method''' does '''override''' a '''method''' declared in a '''superclass'''.
+| If a '''method '''is annotated with '''@Override''', compiler generates '''error '''if:
 |-
 | 08:23
-| The '''method signature '''is different in its '''superclass.'''
+|* The '''method signature '''is different in its '''superclass.'''
 |-
 | 08:28
-| Now, let us come back to the '''IDE.''' Come back to the '''Manager class.'''
+| Now, let us come back to the '''IDE.''' Come back to the '''Manager class'''.
 |-
 | 08:34
-| The '''at sign''' character indicates the compiler that what follows is an '''annotation.'''
+| The '''at (@)''' sign character indicates the compiler that what follows is an '''annotation.'''
 |-
 | 08:42
-| Here, it shows that the '''getDetails method '''is '''overridden.'''
+| Here, it shows that the '''getDetails()''' method is '''overridden.'''
 |-
@@ Line 333: / Line 337: @@
 |-
 | 08:51
-| Save the file and run the program.
+| Save the file and '''run''' the program.
 |-
 | 08:55
-| We get the '''output''' as follows.
+| We get the '''output''' as follows:
 '''Name: Nikkita Dinesh'''
 '''Email: abc@gmail.com'''
 '''Manager of Accounts'''
@@ Line 352: / Line 358: @@
 |-
 | 09:16
-| In this way, we override the '''method''' of the '''parent class '''by the '''subclass'''.
+| In this way, we '''override''' the '''method''' of the '''parent class '''by the '''subclass'''.
 |-
 | 09:23
-| Let us summarize.
+| Let us summarize. In this tutorial, we have learnt about:
-In this tutorial we have learnt about
+*'''Subclassing''' and
-'''Subclassing''' and
+*'''Method Overriding'''.
 '''Method Overriding'''
 |-
 | 09:31
-| As an '''assignment''' Create a '''class Vehicle '''which has a method '''run '''that prints “'''The Vehicle is running.”'''
+| As an '''assignment''', create a '''class Vehicle '''which has a method '''run '''that prints “'''The Vehicle is running.”'''
 |-
@@ Line 375: / Line 380: @@
 |-
 | 09:52
-| To know more about the Spoken Tutorial Project
+| To know more about the Spoken Tutorial Project, watch the video available at the following link. It summarizes the Spoken Tutorial project. If you do not have good bandwidth, you can download and watch it.
-Watch the video available at the following link
 It summarizes the Spoken Tutorial project
 If you do not have good bandwidth, you can download and watch it
 |-
 | 10:06
-|The Spoken Tutorial Project Team
+|The Spoken Tutorial Project Team:
-Conducts workshops using spoken tutorials
+*Conducts workshops using spoken tutorials
-Gives certificates for those who pass an online test
+*Gives certificates for those who pass an online test.
-For more details, please write to '''contact at spoken hyphen tutorial dot org'''
+For more details, please write to '''contact at spoken hyphen tutorial dot org'''.
 |-
 | 10:21
-|Spoken Tutorial Project is a part of the Talk to a Teacher project.
+|'''Spoken Tutorial''' Project is a part of the '''Talk to a Teacher''' project. It is supported by the National Mission on Education through ICT, MHRD, Government of India.
-It is supported by the National Mission on Education through ICT, MHRD, Government of India.
+More information on this mission is available at:
-More information on this Mission is available at
+'''http://spoken-tutorial.org/NMEICT- Intro'''
 http://spoken-tutorial.org/NMEICT- Intro
 |-
 | 10:42
-| This is '''Arya Ratish '''from '''IIT Bombay '''signing off.
+| This is Arya Ratish from '''IIT Bombay''', signing off.
 Thanks for joining.
 |}