Difference between revisions of "Java/C2/Creating-object/English-timed"
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| − | | In this tutorial, we will learn about: | + | | In this tutorial, we will learn about: '''Reference Variables''' |
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| − | + | Constructing '''objects''' and Memory Allocation for '''objects'''. | |
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| 00:13 | | 00:13 | ||
| − | | Here, we are using : | + | | Here, we are using : '''Ubuntu 11.10''', '''JDK 1.6''' and '''Eclipse IDE 3.7.0''' |
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| 00:29 | | 00:29 | ||
| − | |If not, please see the Spoken Tutorial on these topics available at | + | |If not, please see the Spoken Tutorial on these topics available at '''Spoken''' hyphen '''Tutorial''' dot org. |
| − | '''Spoken''' hyphen '''Tutorial''' dot org. | + | |
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| 00:38 | | 00:38 | ||
| − | + | | We know that '''variables''' and '''methods''' together form the members of a '''class'''. | |
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|00:48 | |00:48 | ||
| − | + | | Now, let us see what an '''object''' is. | |
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| 00:52 | | 00:52 | ||
| − | |An '''object''' is an '''instance''' of a class. | + | |An '''object''' is an '''instance''' of a '''class'''. |
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| − | | Let us go back to the '''Student class''' which we have already created in the earlier | + | | Let us go back to the '''Student class''' which we have already created in the earlier tutorial. |
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| − | |Now create another '''class''' named '''TestStudent''' inside the same '''project.''' | + | |Now, create another '''class''' named '''TestStudent''' inside the same '''project.''' |
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| − | |In this '''class''' I have the '''main method.''' | + | |In this '''class''', I have the '''main method.''' |
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| − | |'''Student''' space '''stud1''' equal to '''new''' space '''Student''' opening and closing brackets | + | |'''Student''' space '''stud1''' equal to '''new''' space '''Student''' opening and closing brackets semicolon. |
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| − | | | + | |04:47 |
| Now, type: next line '''System''' dot '''out''' dot '''println''' within brackets and double quotes '''stud2 contains''' space plus '''stud2''' and then semicolon. | | Now, type: next line '''System''' dot '''out''' dot '''println''' within brackets and double quotes '''stud2 contains''' space plus '''stud2''' and then semicolon. | ||
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| − | | | + | | 05:44 |
| Now, we can make a change here. | | Now, we can make a change here. | ||
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| 06:34 | | 06:34 | ||
| − | | | + | | Reference variables, Creating object using new operator |
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| 06:38 | | 06:38 | ||
| − | | | + | |And assigning references. |
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| − | + | | The Spoken Tutorial project team: | |
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| 07:10 | | 07:10 | ||
| − | | Gives certificates | + | | Gives certificates to those who pass an online test. |
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| 07:31 | | 07:31 | ||
| − | | More information on this mission is available at | + | | More information on this mission is available at [http://spoken-tutorial.org/NMEICT-Intro]. |
| − | [http://spoken-tutorial.org/NMEICT-Intro]. | + | |
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Latest revision as of 15:21, 28 March 2017
| Time | Narration |
| 00:01 | Welcome to the spoken tutorial on Creating objects. |
| 00:05 | In this tutorial, we will learn about: Reference Variables
Constructing objects and Memory Allocation for objects. |
| 00:13 | Here, we are using : Ubuntu 11.10, JDK 1.6 and Eclipse IDE 3.7.0 |
| 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. |
| 01:04 | Object stores its state in fields or variables. |
| 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 | Now, Save 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 | Now, inside the main method I will create an object of the Student class. |
| 02:11 | For that, inside the main method, type: |
| 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. |
| 03:09 | Now, let us see what stud1 contains. |
| 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 semicolon. |
| 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 refer 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 refer 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, 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 [1]. |
| 06:58 | It summarizes 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 to 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 [2]. |
| 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
