Difference between revisions of "Java/C2/Parameterized-constructors/English-timed"
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Revision as of 14:43, 9 July 2014
| Time | Narration |
| 00:02 | Welcome to the Spoken Tutorial on parameterized constructor in java. |
| 00:08 | In this tutorial we will learn |
| 00:10 | About a parametrized constructor |
| 00:13 | And to create a parameterized constructor
|
| 00:17 | Here we are using
|
| 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 parameterized constructor? |
| 00:48 | A constructor that have parameter is called a parameterized constructor.
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| 00:55 | It can have one or more than one parameter. |
| 00:59 | Let us now create a parameterized constructor.
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| 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.
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| 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 paranthesis 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 parameterized 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.
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| 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.
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| 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 parameterized constructor. |
| 10:36 | Functionality of parameterized 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. |
| 10:53 | To know more about the Spoken Tutorial Project |
| 10:56 | Watch the video available at http://spoken-tutorial.org/What_is_a_Spoken_Tutorial |
| 11:02 | It summarizes the Spoken Tutorial project |
| 11:06 | If you do not have good bandwidth, you can download and watch it
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| 11:10 | The Spoken Tutorial Project Team |
| 11:12 | Conducts workshops using spoken tutorials |
| 11:14 | Gives certificates for those who pass an online test |
| 11:18 | For more details, please write to contact@spoken-tutorial.org
|
| 11:24 | Spoken Tutorial Project is a part of the Talk to a Teacher project |
| 11:28 | It is supported by the National Mission on Education through ICT, MHRD, Government of India |
| 11:34 | More information on this Mission is available at
|
| 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. |
