Java/C2/Default-constructor/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:02 | Welcome to the Spoken Tutorial on Default constructor in java. |
| 00:07 | In this tutorial, we will learn: |
| 00:10 | About the default constructor. |
| 00:12 | And to create a constructor. |
| 00:15 | Here we are using:
Ubuntu version 11.10 Java Development Environment jdk 1.6 and Eclipse 3.7.0 |
| 00:26 | To follow this tutorial, you must know |
| 00:29 | how to create a class and the object of the class in java using eclipse. |
| 00:34 | If not, for relevant tutorials, please visit our website which is as shown.http://www.spoken-tutorial.org |
| 00:42 | Constructor is used to initialize the instance variables. |
| 00:46 | It is called at the creation of new object. |
| 00:50 | Let us now see how a constructor is defined in java. |
| 00:55 | So, in the eclipse, I have already created a java file Student.java. |
| 01:02 | In the Student class we will declare two variables. |
| 01:07 | So type int roll_number semi-colon and String name semicolon. |
| 01:20 | Now let us create a method. |
| 01:22 | So, type: void studentDetail(). |
| 01:33 | Within curly brackets, type: System dot out dot println roll_number; |
| 01:50 | Then System dot out dot println name;. |
| 02:03 | Now in main method we will call this method. |
| 02:08 | So, let us create an object and call the method. |
| 02:14 | So, type: Student object name stu equal to new Student(). |
| 02:28 | Then stu dot method name i.e studentDetail. |
| 02:41 | Save and Run the program. |
| 02:46 | We see the output 'zero' and 'null'. |
| 02:49 | So, the int variable roll_number has been initialized to its default value 'zero'. |
| 02:56 | And the String name has been initialized to its default value 'null'. |
| 03:02 | If we do not define a constructor then a default constructor is created. |
| 03:08 | Default constructor has no parameters. |
| 03:11 | It initializes the instance variables to their default value. |
| 03:16 | Now let us define a constructor. |
| 03:18 | So, type: Student S capital parenthesis and curly brackets. |
| 03:30 | Remember, the Constructor has the same name as the 'class name' to which it belongs. |
| 03:38 | Constructors are also similar to methods but there are some important differences. |
| 03:44 | Save and Run the program. |
| 03:48 | We see the same output. |
| 03:51 | This is because the constructor that we defined is same as having no constructor. |
| 03:58 | But here, no default constructor is created because we have defined a constructor. |
| 04:06 | Now, let's give values to our variables. |
| 04:11 | So, inside the constructor type: roll_number equal to ten semicolon. |
| 04:25 | And name equal to within double quotes Raman. |
| 04:35 | Now Save and Run the program. |
| 04:43 | We see in the output that the roll_number is ten and the name is Raman. |
| 04:50 | So, the constructor initializes the instance field. |
| 04:55 | Now, let us see some differences between method and a constructor. |
| 05:01 | Constructor does not have a return type. |
| 05:05 | whereas method has a return type. |
| 05:10 | Constructor is called using the new operator. |
| 05:16 | whereas the method is called using the dot operator. |
| 05:21 | So, these were some differences between constructor and method. |
| 05:29 | So, in this tutorial, we have learnt: |
| 05:32 | About the default constructor. |
| 05:34 | To define a constructor. |
| 05:36 | And Differences between method and constructor. |
| 05:41 | For self assessment, create a class Employee with variables and a method to display variables. |
| 05:47 | And create a constructor for the class Employee. |
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| 06:38 | This brings us to the end of the tutorial. |
| 06:40 | Thanks for joining. |
| 06:42 | This is Prathamesh Salunke, signing off. Jai Hind. |
