Java/C3/Using-final-keyword/English

Title of script: USING FINAL KEYWORD

Author: Trupti Rajesh Kini

Keywords: video tutorial, final keyword, final variable, final method, final class

Visual Cue	Narration
Slide 1	Welcome to the spoken-tutorial on Using final keyword.
Slide 2	In this tutorial we will learn about The final keyword and when to invoke it. We will also learn about - final variables, final methods, final classes
Slide 3 Software Requirements	To record this tutorial, I am using Ubuntu Linux version 12.04 JDK 1.7 Eclipse 4.3.1
Slide 4 Pre-requisites	To follow this tutorial, you must have, Basic knowledge of Java and Eclipse IDE. and knowledge of Subclassing and Method overriding. If not, for relevant Java tutorials, please visit our website.
Slide 5 final keyword	First of all, we will learn what final keyword is. final is a keyword or reserved word in Java. It can be applied to variables, methods or classes.
What is final variable? Slide 6	Now, let us learn what final variable is. final variable is a variable whose value cannot be changed. That is, it will be a constant.
Go to the Eclipse IDE Point to MyProject	I am switching to Eclipse IDE now. I had already created a project named MyProject in the previous tutorial.
Go to the Employee class	So we will directly go to the Employee class of the project.
Point to the variable name	Come to the variable name.
Type final keyword Highlight variable name	Add final keyword before the variable name. We have made the variable name as final.
Type sneha	We will initialize the variable name with value sneha.
Save and Run the program.	We will Save and Run the program.
Highlight the error The final field Employee.name cannot be assigned	We get compilation error. The final field Employee.name cannot be assigned
Highlight public final string name = “sneha”	This is because here the final variable name is already declared and initialised. We can initialize a final variable only once.
Comment the method setName	So we will comment the method setName which modifies the variable name.
Save the class.	Save the class.
Go to TestEmployee class->main method Type // before manager.setName("Nikkita Dinesh");	Now, come to TestEmployee class. Come to the main method and comment the line manager.setName("Nikkita Dinesh"); We commented this line as it was instance of method setName. We have already commented setName method in Employee class.
Save and Run the program.	Now let us Save the class and Run the program.
Highlight the output Name: Sneha Email: abc@gmail.com Manager of: Accounts	Great!!! We got the output, Name: Sneha Email: abc@gmail.com Manager of: Accounts
Highlight the initialization in TestEmployee class and Employee class.	We got this output as we already initialized variables with these values in TestEmployee class and Employee class.
Go to Employee class->final variable name	Now come to the final variable name. in Employee class.
Remove the initialization “sneha”	Remove the initialization of final variable name. That is remove “sneha”.
Go to the method setName Uncomment the method.	Uncomment the method setName.
Save and run the program.	Save and Run the program.
Highlight the error The final field Employee.name cannot be assigned	We get the error, The final field Employee.name cannot be assigned
	This is because, If the final variable is not initialised, then only constructor can initialize it. That is it cannot be modified anywhere else in the program.
Go to Employee class	For that, let’s create a constructor in the Employee class. We have already learnt what a constructor is earlier.
	We know that constructor has the same name as class name.
Type, Employee() { name="Sneha"; }	So we will type Employee, parentheses, open and close curly brackets and inside the curly brackets, lets initialize the variable name with value sneha. semicolon .
Point to the method setName Comment the method	Comment the method setName.
Save and Run the program.	Save and Run the program.
Highlight the output Name: Sneha Email: abc@gmail.com Manager of: Accounts	We got the desired output.
	final variable is successfully initialized in a constructor.
	Now we will learn about final static variables.
Go to the Employee class	Come to the final variable in Employee class.
Type static before final keyword	Add static keyword before final keyword We have made the final variable as static.
Save & Run the program.	Save and Run the program.
Highlight the error The final field Employee.name cannot be assigned	We get error. The final field Employee.name cannot be assigned
Slide 7	This is because static final variables cannot be initialized in the constructor. They must be assigned a value with their declaration. Or they must be declared in a static block.
Slide 8	static variables are shared among all the objects of a class. Creating a new object would change the static variable. This is not allowed if the static variable is final.
Go to Eclipse IDE	Switch back to Eclipse IDE.
Go to the Employee class ->Employee() Delete Employee() and type static. Highlight static block	So now we will create a static block. For that, in the Employee class, come to the constructor. we created Here instead of Employee(), we will type static. We have created a static block.
Now we will Save and Run the program.	Now we will Save and Run the program.
Highlight the output, Name: Sneha Email: abc@gmail.com Manager of: Accounts	We got the desired output, We have successfully initialized static final variable.
	Now let’s use final variable as a parameter to the method.
Go to the method setEmail	Come to the method setEmail. in Employee class.
Type final before String newEmail	Add final keyword before String newEmail We have made the parameter as final.
Save and Run the program.	Save and Run the program.
Highlight the output Name: Sneha Email: abc@gmail.com Manager of: Accounts	We got the desired output,
Come to the method setEmail Type newEmail="abc@gmail.com";	Now, come to the method setEmail. Inside the method we will type, newEmail is equal to abc@gmail.com semicolon. We have modified the final variable newEmail.
Save & Run the program.	Once again we will Save & Run the program.
Highlight the error, The final local variable newEmail cannot be assigned.	We get error. The final local variable newEmail cannot be assigned.
	This is because final variable as parameter to a method cannot be modified by that method. So lets remove the variable modification.
	Now we will learn about final method.
Come to the method getDetails in employee class.	Come to the method getDetails in employee class.
Type final keyword before getDetails.	Add final keyword before method getDetails.
Save and Run the program.	Save and Run the program.
Point to the compilation error, class Manager overrides final method getDetails.()	We get error, class Manager overrides final method getDetails.()
Highlight method getDetails() in Manager class.	Come to the method getDetails() in Manager class.
Highlight method getDetails() in Manager class.	This is because if you make any method as final, you cannot override it. Manager class method getDetails overrides getDetails method in Employee class.
Slide 9	What if final method is private? private methods are not inherited by the child class. So we can add a method getDetails() in the child class. You can try this as an assignment.
Go to Eclipse IDE	Switch back to Eclipse IDE.
Go to Employee class >> remove final keyword>> Remove static keyword	In Employee class, remove final keyword before method getDetails. Remove static keyword before final variable name.
Instead of static Type, Employee()	Now we will learn whether constructor can me declared as final or not For that we will again create a constructor. So instead of static we will type, Employee parentheses.
Type final before the constructor	Add final keyword before the constructor.
Save and run the program.	Save and run the program.
Highlight compilation error, Illegal modifier for the constructor in type Employee	We get error Illegal modifier for the constructor in type Employee
Remove the final keyword before Employee()	This is because, constructor cannot be final since constructors are not inherited. We will remove the final keyword before the constructor.
	Now, we will learn about final class.
Type final keyword before the class Employee.	Add final keyword before the class Employee. to make it final.
Save and Run the program.	Save and Run the program.
Highlight the compilation error, The method setEmail is undefined for the type Manager	We get an error, The method setEmail is undefined for the type Manager
Come to TestEmployee class and comment the lines. manager.setEmail("abc@gmail.com"); manager.setDepartment("Accounts");	To know the actual error, lets come to TestEmployee class and comment the lines. manager.setEmail("abc@gmail.com"); manager.setDepartment("Accounts");
Save the class and run the program	Save the class and run the program
Highlight the compilation error, The type Manager cannot subclass the final class Employee	The actual error is The type manager cannot subclass the final class Employee. Here Manager class extends Employee class.
Come back to Employee class and remove the final keyword	So lets come back to Employee class and remove the final keyword.
Come to the TestEmployee class Uncomment the lines manager.setEmail("abc@gmail.com"); manager.setDepartment("Accounts");	Come to the TestEmployee class. Uncomment the lines manager.setEmail("abc@gmail.com"); manager.setDepartment("Accounts");
Save the class and run the program.	Save the class and run the program.
Highlight the output Name: Sneha Email: abc@gmail.com Manager of: Accounts	We got the desired output.
Slide 10 Summary	Now lets summarize In this tutorial we learnt: When to invoke final keyword. What are: final variables, final methods and final classes
Slide 11 Assignment	As an assignment, Repeat the steps of Using final keyword tutorial for the Bike and Vehicle class. which we used in the previous tutorial. Write down the classes in java that are final classes.
Slide 12 About Spoken Tutorial Project	Watch the video available at the following link http://spoken-tutorial.org/What is a Spoken Tutorial It summarizes the Spoken Tutorial project If you do not have good bandwidth, you can download and watch it
Slide 13 About Spoken Tutorial workshops	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
Slide 14 Acknowledgement	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 This is Trupti Kini from IIT Bombay signing off. Thanks for joining.

Contributors and Content Editors

Nancyvarkey, Trupti