View source for Java/C3/Java-Interfaces/English-timed

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

|-
| 00:01
|  Welcome to the''' Spoken Tutorial''' on''' Java Interfaces'''.

|-
| 00:05
|  In this tutorial, we will learn about: * Creating an''' interface'''

|-
|  00:10
| * Creating ''' Implementation classes''' and * Usage of  Interface'''.

|-
| 00:16
|  For this tutorial, I am using:

'''Ubuntu 12.04'''

'''JDK 1.7 '''and

'''Eclipse 4.3.1'''

|-
| 00:28
|  To follow this tutorial, you should have knowledge of basics of''' Java''' and''' Eclipse IDE.'''

|-
|  00:36
|You should also have the knowledge of''' subclassing''' and''' Abstract classes '''in''' Java.'''

|-
|  00:42
|If not, for relevant Java tutorials, please visit the link shown.

|-
|  00:48
|  First let's understand what is an '''interface'''.

|-
| 00:52
| An Interface contains a set of''' abstract''' methods and''' static data members'''.

|-
|  00:58
|It defines the signatures of a set of '''methods''' without the body.

|-
|  01:04
|It is declared using the '''interface''' keyword.

|-
| 01:08
| Now we will switch to''' Eclipse''' and create a new project called''' InterfaceDemo'''.

|-
|  01:15
|Here, we will create the necessary''' classes''' and''' interface''' to demonstrate the usage of''' interfaces.'''

|-
| 01:24
| Right-click on''' src''' folder and click''' New > Interface'''.

|-
|  01:30
|Type the name as''' Animal''' and press '''Enter'''.

|-
|  01:34
|Note that the '''“interface”''' keyword is used for defining an interface.

|-
|  01:39
|Now type the code as displayed on the screen.

|-
| 01:43
| Here, the '''interface''' name is''' Animal.'''

|-
|  01:46
|It contains three abstract methods''' talk(), see()''' and''' move().'''

|-
|  01:52
|All such '''methods''' in an interface are implicitly''' public''' and''' abstract'''.

|-
|  01:59
|An''' interface''' can also contain '''constant variable''' declarations.

|-
|  02:04
|Here, the constant string value “Mammal” is assigned to the variable “type1”.

|-
|  02:12
|And “Reptiles” is assigned to the variable “type2”.

|-
|  02:16
|All''' constant''' values defined in an''' interface''' are implicitly''' public, static''' and''' final.'''

|-
| 02:25
| Next we will see '''implementation class''' for an''' interface''' with an example.

|-
| 02:32
| Here,''' Human''' is a class which implements the''' Animal''' interface.

|-
|  02:38
|So, it must provide implementations for the methods''' talk(), see()''' and''' move().'''

|-
|02:45
| A '''class''' can also implement multiple interfaces.

|-
|  02:49
|As shown in the example, the class '''Human''' implements two interfaces '''Animal''' and''' Action.'''

|-
|  02:57
|Note that a''' comma operator''' used in the syntax is to identify the different  interfaces. 

|-
|  03:04
|Now this''' class''' should provide implementations to all the''' abstract methods''' in both''' Animal''' and''' Action''' interfaces.

|-
| 03:13
| The figure here represents an implement relation.

|-
|  03:18
|The''' Animal''' class is an''' interface.'''

|-
|  03:22
|The''' Human''' and''' Snake''' classes are the two '''implementation classes.'''

|-
|  03:28
|The '''Human''' class provides its own different implementations for''' talk()''',''' see()''' and''' move()''' methods.

|-
|  03:36
|And, the '''Snake''' class provides its own different implementations for '''talk(), see()''' and '''move()''' methods.

|-
| 03:45
| Let us understand the usage of '''interfaces '''with a sample program.

|-
| 03:50
|  Right-click on the '''default package''' and create a''' class''' called''' Human.'''

|-
|  03:56
|Now, to make this an '''implementation class''' of''' Animal''', type: '''implements Animal'''.

|-
|  04:04
|  Now, we can see an error comes up in the''' Eclipse IDE.''' 

|-
|  04:09
|This error indicates that we should provide an '''implementation''' to the '''Animal interface.'''

|-
|  04:15
|  Let us see how to rectify this error.

|-
| 04:19
|  Now let us define the methods '''talk(), see()''' and''' move().'''

|-
|  04:23
|So, type:''' public void talk( )''' within curly brackets type '''System.out.println''' within quotes "I am a human and I belong to".

|-
|  04:37
|Now we can use the value of the''' static, final variable type1''' declared in the''' Animal''' interface.

|-
|  04:45
|So, type: '''+ Animal.type1+''' within quotes "family" semicolon.

|-
|  04:54
|Let us now implement the '''see()''' method.

|-
|  04:57
|So, type:''' public void see( )''' within curly brackets type '''System.out.println''' within quotes "I can see all colors" semicolon.

|-
|  05:11
|We should also define the''' move()''' method.

|-
|  05:14
|So, type:''' public void move( )''' within curly brackets type '''System.out.println''' within quotes "I move by walking" semicolon.

|-
|  05:29
|Note that the error disappears, once all the '''methods''' are implemented.

|-
|  05:34
|  Next we will see how to define the''' Snake''' class.

|-
| 05:38
|  I have already created it in my '''project'''.

|-
|  05:42
|Please create the '''snake class''' in your '''project''' and type the following code as displayed on the screen.

|-
|  05:49
|Now let us go through the code. 

|-
| 05:52
|  We can see that all the '''methods''' of the''' Animal interface- talk(), see()''' and''' move()''' are implemented inside this '''class'''.

|-
|  06:01
|Here, the''' talk()''' method prints “I am a snake and I belong to”.

|-
|  06:07
|Then the value of''' Animal.type2''' is to be printed and then “family”.

|-
|  06:13
|Here, the''' see()''' method prints “I can see only in black and white”.

|-
|  06:19
|The''' move()''' method prints "I move by crawling".

|-
| 06:23
|  Note that the''' Human''' class has its own implementations of''' talk(), see()''' and''' move()''' methods.

|-
|  06:31
|And, the''' Snake''' class has its own implementations of''' talk(), see()''' and''' move()''' methods.

|-
|  06:39
|  Now, right-click on the default package, click''' new >  class''' and then type the name as''' Demo.'''

|-
|  06:47
|Inside this '''class''', we will have the''' main''' method.

|-
|  06:51
|So, type''' main''' and then press '''ctrl+space''' to generate the''' main''' method.

|-
|  06:58
|  Type the following code as displayed on the screen.

|-
|  07:01
|In this line, we instantiate the ''' Human class''' using the''' Animal''' interface.

|-
|  07:07
|This is represented as '''Animal h''' equals''' new Human()''';

|-
|  07:14
|Now we can invoke the different methods using this '''object''' as '''h.talk(); h.see();   h.move();'''

|-
|  07:26
|  Next, we instantiate the''' Snake''' class using the''' Animal''' interface.

|-
|  07:31
|Now we can invoke the different methods using this '''object''' as shown.

|-
|  07:38
|  Now, let us '''run''' this''' Demo''' program.

|-
|  07:41
|  So, right-click on the class ''' Demo''' and then select''' Run as > Java Application'''.

|-
| 07:48
|  We can see the output. 

|-
|  07:52
|These are printed by the''' talk(), see()''' and''' move()''' methods invoked using the''' human class object h'''.

|-
|  08:00
|  These are printed by the''' talk(), see()''' and''' move()''' methods invoked using  the''' Snake class object s'''.

|-
| 08:08
| Now, let us explore the differences between an''' interface''' and an''' abstract class'''.

|-
|08:14
| All the methods in an interface should be''' abstract.'''

|-
|  08:18
|Within interface, there should not be any  '''constructors''',

|-
|  08:23
| '''concrete methods''',  '''static methods '''and '''main method'''.

|-
|  08:28
|But an''' abstract class''' can have all these inside it.

|-
|  08:32
|The variables in an interface should be''' static''' and''' final.''' 

|-
|  08:38
|There are no such restrictions for an '''abstract class'''.

|-
|  08:43
|  This brings us to the end of this tutorial. Let us summarize.

|-
|  08:48
|  In this tutorial, we have learnt about: * Creating an''' Interface'''

|-
|  08:53
| * Creating an''' implementation class''' and

|-
|  08:56
|* Usage of''' interfaces'''.

|-
|  08:59
|  As an assignment, create an interface '''Vehicle''' which contains the methods '''brake()''' and''' run()'''.

|-
|  09:07
|  Create another interface '''Fuel''' which contains the following methods.   '''fill(String type,int quantity)''', '''pay(int quantity,int price)'''.

|-
| 09:19
|  Create a subclass''' Car''' which implements both interfaces''' Vehicle''' and''' Fuel.'''

|-
|  09:26
|Here,''' brake''' method should print "Car Applies Power brake". 

|-
|  09:30
|And the '''run''' method must print "Car is running on 4 wheels".

|-
|  09:35
|  Similarly''' fill()''' method can print the type and quantity of the fuel filled.

|-
|  09:41
|For example: 10 Litres of petrol.

|-
|  09:44
|  '''pay()''' method can be used to print price to be paid. For example: Pay Rs. 640

|-
| 09:53
|Create another subclass''' Bike''' which again implements both the interfaces '''Vehicle''' and''' Fuel'''.

|-
|  10:00
|Here, '''brake''' method can print "Bike Applies hand brake". 

|-
|  10:05
|And the '''run''' method can print “Bike is running on 2 wheels”.

|-
|  10:10
|Next, implement the '''fill()''' and '''pay()''' methods as explained earlier.

|-
|  10:15
|Finally create a '''Demo class''' containing the '''main''' method to verify the results.

|-
|  10:21
|  This video at the following link summarizes the Spoken Tutorial Project. Please download and watch it.

|-
| 10:29
|  The Spoken Tutorial Project Team: Conducts workshops using spoken tutorials and 

Gives certificates on passing the online tests.

|-
|  10:38
| For more details, please write to us.

|-
|  10:41
| '''Spoken Tutorial Project''' is funded by NMEICT, MHRD, Government of India.

|-
|  10:48
|More information on this mission is available at the link shown.

|-
|  10:52
|This script has been contributed by: Department of Information Technology, Amal Jyothi College of Engineering.

|-
|  11:01
|This is Priya from '''IIT Bombay''', signing off. Thanks for joining.

|}