Difference between revisions of "Java/C2/Creating-object/English-timed"
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Revision as of 14:39, 2 January 2014
| Time' | Narration |
| 00:01 | Welcome to the spoken tutorial on Creating objects. |
| 00:05 | In this tutorial we will learn about:
|
| 00:13 | Here, we are using :
|
| 00:23 | To follow this tutorial you must know how to create a simple class using Eclipse.
|
| 00:29 | If not please see the spoken-tutorial on these topics available at
spoken hyphen tutorial dot org. |
| 00:38 | We know that variables and methods together form the members of a class.
|
| 00:43 | To access the members of a class , we need to create an object for the class. |
| 00:48 | Now let us see what an object is.
|
| 00:52 | An object is an instance of a class.
|
| 00:55 | Each object consist of state and behavior.
|
| 00:58 | Recall the example of human being class we had discussed in the earlier tutorial.
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| 01:04 | Object stores its state in fields or variables.
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| 01:08 | It exposes its behavior through methods.
|
| 01:11 | Now let us learn about reference variables.
|
| 01:15 | We know about the 8 primitive data types in Java.
|
| 01:19 | All other types refer to objects rather than primitives.
|
| 01:23 | Variables that refer to objects are reference variables. |
| 01:28 | Let us go back to the Student class which we have already created in the earlier tutorial.
|
| 01:37 | Now, let me remove the main method from this class.
|
| 01:49 | NowSave the file by pressing Control and S keys simultaneously.
|
| 01:55 | Now create another class named TestStudent inside the same project.
|
| 02:00 | I have already created it.
|
| 02:03 | In this class I have the main method.
|
| 02:06 | No inside the main method I will create an object of the Student class.
|
| 02:11 | For that, inside the main method, type
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| 02:17 | Student space stud1 equal to new space Student opening and closing brackets, semicolon.
|
| 02:34 | Thus we have created an object of the Student class.
|
| 02:37 | Here, Student is the name of the class for which the object is to be created.
|
| 02:47 | stud1 is a reference variable referring to one object of the Student class.
|
| 02:53 | And the new keyword allocates space for the new object to be created.
|
| 02:59 | Please note that stud1 is not the object of the Student class.
|
| 03:03 | It only holds the reference of the new object created.
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| 03:09 | Now, let us see what stud1 contains.
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| 03:13 | So next line type System dot out dot println within brackets and double quotes stud1 contains space plus stud1 and then semicolon.
|
| 03:44 | Now, save and run the file TestStudent dot java. |
| 03:53 | We get the output as follows.
|
| 03:56 | So here Student is the name of the class of the new object created.
|
| 04:03 | The second part is the memory address of the new object created.
|
| 04:08 | We can access the fields and methods of the Student class using stud1.
|
| 04:15 | We will learn about these in the coming tutorials. |
| 04:18 | Now, I will create one more object of the Student class.
|
| 04:24 | So, I will type Student space stud2 equal to new space Student opening and closing brackets semi-colon. |
| 04:47 | Now type next line System dot out dot println within brackets and double quotes stud2 contains space plus stud2 and then semicolon.
|
| 05:19 | Now, let us save and run this file. |
| 05:25 | We can see that here stud1 and stud2 refers to two different objects.
|
| 05:31 | That is, stud1 and stud2 are referring to two different students.
|
| 05:37 | They have different roll numbers and names. |
| 05:44 | Now, we can make a change here.
|
| 05:51 | Here type Student stud2 equal to stud1.
|
| 06:01 | Now, save and run this file.
|
| 06:06 | We can see that here both stud1 and stud2 refers to the same object.
|
| 06:12 | That means both stud1 and stud2 are referring to the same student with a roll number and name. |
| 06:31 | So in this tutorial we learnt about |
| 06:34 | Reference variables |
| 06:35 | Creating object using new operator |
| 06:38 | And Assigning references
|
| 06:41 | For self assessment |
| 06:43 | create another class named TestEmployee. |
| 06:46 | Create an object of the Employee class with reference variable as emp1.
|
| 06:52 | To know more about the spoken tutorial project. |
| 06:55 | Watch the video available at http://spoken-tutorial.org/What_is_a_Spoken_Tutorial |
| 06:58 | It summarises the Spoken Tutorial project |
| 07:01 | If you do not have good bandwidth, you can download and watch it
|
| 07:05 | The Spoken Tutorial Project Team |
| 07:07 | Conducts workshops using spoken tutorials |
| 07:10 | Gives certificates for those who pass an online test |
| 07:14 | For more details, please write to contact@spoken-tutorial.org
|
| 07:20 | Spoken Tutorial Project is a part of the Talk to a Teacher project |
| 07:24 | It is supported by the National Mission on Education through ICT, MHRD, Government of India |
| 07:31 | More information on this Mission is available at
http://spoken-tutorial.org/NMEICT-Intro
|
| 07:40 | Thus we have come to the end of this tutorial. |
| 07:43 | This is Arya Ratish from IIT Bombay signing off. |
| 07:46 | Thanks for joining us. |
Contributors and Content Editors
Arya Ratish, Devisenan, Gaurav, PoojaMoolya, Sandhya.np14, Sneha
