Difference between revisions of "Java/C3/Java-Interfaces/English-timed"

|  Welcome to the''' Spoken Tutorial''' on''' Java Interfaces'''

|  In this tutorial we will learn about: Creating an''' interface'''

| Creating an''' Implementation classes''' and  Usage of  Interface'''

| For this tutorial, I am using

* '''Ubuntu 12.04'''

* '''JDK 1.7 '''and

* '''Eclipse 4.3.1'''

|If not, for relevant''' Java''' tutorials, please visit the link shown.

| An''' Interface''' contains a set of''' abstract''' '''methods''' and''' static data members'''.

|Here we will create the necessary''' classes''' and''' interface''' to demonstrate the usage of''' interfaces.'''

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

|Note that the '''“interface”''' keyword is used for defining an '''interface'''.

|Now type the code as displayed on the screen

| Here the the '''interface''' name is''' Animal.'''

|Here, the constant string value''' “Mammal”''' is assigned to the variable''' “type1”'''.

|And''' “Reptiles”''' is assigned to the variable''' “type2”'''.

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

| Here''' Human''' is a''' class''' which implements the''' Animal interface.'''

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

| A '''class''' can also implement''' multiple interfaces'''.

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

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

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

|The''' Animal class''' is an''' interface.'''

|The''' Human''' and''' Snake classes''' are the two '''implementation classes.'''

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

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

|  Right click on the '''default package''' and create a''' class''' called''' Human.'''

|Now, to make this an '''implementation class''' of''' Animal, '''type''' implements Animal'''

|  Now we can see an error comes up in the''' Eclipse IDE.'''  

|This error indicates that, we should provide an '''implementation''' to the '''Animal interface.'''

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

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

|Now we can use the value of the''' static, final variable type1''' declared in the''' Animal interface'''

|So type, '''+ Animal.type1+''' within quotes''' family '''semicolon.

|Let us now implement the '''see() method'''.

|So type''' public void see( )''' within curly brackets type '''System.''out''.println''' within quotes''' I can see all colors''' semicolon

|We should also define the''' move() method'''.

|So type''' public void move( ).''' within curly brackets type '''System.''out''.println''' within quotes''' I move by walking''' semicolon

|  Next we will see how to define the''' Snake class.'''

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

|Here the''' talk() method''' prints “'''I am a snake and I belong to”'''

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

|Here the''' see() method''' prints “'''I can see only in black and white”'''

|The''' move() method''' prints''' "I move by crawling"'''

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

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

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

|Inside this '''class''' we will have the''' main method''',

|So type''' main''' and then press ctrl+space to generate the''' main method.'''

|In this line we instantiate the ''' Human class''' using the''' Animal interface.'''

|Now we can invoke the different '''methods''' using this '''object''' as '''h.talk()''', '''h.see();'''

'''h.move();'''

|  Next, we instantiate the''' Snake class''' using the''' Animal interface'''

|Now we can invoke the different '''methods''' using this '''object''' as shown

|  Now let us run this''' Demo''' program.

|  So right click on the'' class''''' Demo''' and then select''' Run as''' ->''' Java Application'''

|  We can see the output  

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

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

| Now let us explore the differences between an''' interface''' and an''' abstract class'''.

| All the methods in an''' interface''' should be''' abstract.'''

|Within''' interface''' there should not be any  '''constructors'''

| '''concrete methods''',  '''static methods '''and '''main method'''

|The variables in an''' interface''' should be''' static''' and''' final.'''  

|  In this tutorial we have learnt about - Creating an''' Interface'''

| Creating an''' implementation class''' and

| Usage of''' interfaces'''

|  As an''' assignment''' Create an '''interface Vehicle''' which contains the '''methods brake()''' and''' run()'''

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

|Here''' brake method''' should print''' ”Car Applies Power brake”'''

|And the '''run method''' must print''' ”Car is running on 4 wheels”'''

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

|For example: 10 Litres of Petrol.

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

| Create another subclass''' Bike''' which again implements both the '''interfaces Vehicle''' and''' Fuel'''

|Here '''brake method''' can print ”'''Bike Applies hand brake”'''

|And the '''run method''' can print “'''Bike is running on 2 wheels”'''

|Next implement the '''fill()''' and '''pay() methods''' as explained earlier.

|Finally create a '''Demo class''' containing the '''main method''' to verify the results.

|  This video at the following link summarizes the''' Spoken Tutorial Project.''' Please download and watch it.

|  The''' Spoken Tutorial Project Team''' ,  Conducts workshops using spoken tutorials and Gives certificates on passing the online tests.

| For more details, please write to us.

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| This script has been contributed by: '''Deptartment of Information''' '''Technology, Amal Jyothi College of Engineering'''

|This is Priya from IIT Bombay signing off. Thanks for joining.