Java/C2/Parameterized-constructors/English-timed

Time	Narration
00:02	Welcome to the Spoken Tutorial on parametrized constructor in java.
00:08	In this tutorial we will learn:
00:10	* About a parametrized constructor.
00:13	* And to create a parametrized constructor.
00:17	Here we are using: Ubuntu version 11.10 OS Java Development kit 1.6 And Eclipse 3.7.0
00:29	To follow this tutorial, you must know
00:32	how to create a default constructor in java using eclipse.
00:37	If not, for relevant tutorials, please visit our website which is as shown. http://www.spoken-tutorial.org
00:44	What is a parametrized constructor?
00:48	A constructor that has parameter is called a parametrized constructor.
00:55	It can have one or more than one parameters.
00:59	Let us now create a parametrized constructor.
01:03	So in the eclipse, I have Student.java file.
01:09	We created this file in the previous tutorial.
01:15	Now, inside the constructor we will give the variables their default value.
01:21	So roll_number is equal to zero instead of ten.
01:27	And name is equal to null instead of Raman.
01:33	Then type System dot out dot println I am a default constructor.
01:55	So, we have created a constructor with no parameters.
02:00	In java, such constructor is also called a default constructor.
02:07	Now we will create another constructor.
02:11	So, type: Student parentheses.
02:17	Inside parenthesis int the_roll_number comma String the_name.
02:36	So, what we have done is declared a constructor with parameters.
02:43	The name of the constructor Student that is the class name.
02:49	Inside the parentheses, we have given two parameters to the constructor.
02:57	We can give any number of parameters to the constructor.
03:02	Now, inside curly brackets type:
03:05	System dot out dot println I am a parametrized constructor.
03:29	Then roll_number is equal to the_roll_number.
03:43	And name is equal to the_name.
03:53	So we have created a constructor with parameters.
03:58	Now let's call this constructor.
04:02	So in the main method type; student stu2 equal to' new student within parentheses 11 comma in double quotes Raju
04:28	Let's call the studentDetail method.
04:31	So type,stu2.studentDetail.
04:38	Save and Run the program
04:44	We see the output on the console.
04:48	The default constructor is called first.
04:52	It initializes the variables to their default value.
04:56	Then the parameterized constructor is called.
05:00	It initializes the variables to the values that are passed as the argument.
05:05	That is 11 and Raju.
05:08	Let us see how the parametrized constructor works.
05:12	When we call the parameterized constructor, we pass two values to it.
05:18	These are called arguments.
05:22	The value 11 is copied to the parameter the_roll_number.
05:31	And the valueRaju is copied to the parameter the_name.
05:41	Then the value of the_roll_number is assigned to roll_number.
05:50	And the value of the_name is assigned to name.
05:55	Hence in the output we see 11 and Raju.
06:00	Let us see the common errors, when we call a parameterised constructor.
06:07	Suppose we pass a single argument to the constructor.
06:11	So remove Raju.
06:15	We get an error. It states that “The constructor Student with parameter (int) is undefined.”
06:24	So the number of arguments must match the number of parameters.
06:30	Here we can retype Raju and resolve the error.
06:36	Alternatively, what we can do is define another constructor with a single parameter.
06:42	Let us do that
06:45	So Student within paranthesis int r number.
07:01	Inside curly brackets, type System dot out dot println
07:13	I am a constructor with a single parameter.
07:29	Then roll_number is equal to r number
07:48	Save the file.
07:51	We see that the error is resolved when we define the constructor.
07:58	Let's Run the program.
08:02	On the console we see that the roll number is assigned the value 11.
08:08	While name is null since the constructor takes only one argument.
08:18	Let us now call back our constructor with two parameters.
08:23	So type Student stu3 is equal to new Student.
08:40	11 comma Raju.
08:46	ThenStu3 dot studentDetail
08:58	Suppose here we pass 11 as String, so add double quotes.
09:08	We get an error.
09:10	It states that “The constructor Student String commaString is undefined.”
09:17	So even the datatype of the argument must match with that of the parameter.
09:25	So now remove the quotes and Save the file.
09:32	Now we do not see an error.
09:35	So Run the program.
09:38	In the output we see three constructors.
09:42	The first one is the default constructor.
09:45	The second one is theConstructor with one parameter.
09:50	And this third one is theConstructor with two parameters.
09:56	This is how we createParameterised constructor in java.
10:05	Why constructor?
10:07	The variables in a class must be initialized each time an instance is created.
10:13	It can be tedious to initialize all the variables.
10:18	So java allows objects to initialize themselves when they are created.
10:25	This is performed through the use of a constructor.
10:30	So in this tutorial, we have learnt:
10:33	* To create parametrized constructor.
10:36	* Functionality of parametrized constructor.
10:39	And the advantage of using constructor.
10:44	For self assessment, create a class Employee.
10:48	Create constructors with different number of parameters.
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11:43	This brings us to the end of the tutorial.
11:46	Thanks for joining.
11:47	This is Prathamesh Salunke, signing off. Jai Hind.

Contributors and Content Editors

Gaurav, PoojaMoolya, Ranjana, Sandhya.np14, Sneha