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:


  • 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 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


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 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