Difference between revisions of "Java/C2/Creating-object/English-timed"

|  In this tutorial we will learn about:

 

 

* Reference Variables

 

| Here, we are using :

 

* Ubuntu 11.10

* JDK 1.6 and

* Eclipse IDE 3.7.0

 

 

|   To follow this tutorial you must know how to create a simple '''class '''using '''Eclipse'''.

 

|If not please see the '''spoken-tutorial''' on these topics available at  

 

'''spoken '''''hyphen''''' tutorial '''''dot '''''org.'''

| | We know that''' variables''' and '''methods''' together form the '''members''' of a '''class'''.

 

|To access the members of a class , we need to create an object for the class.

| | Now let us see what an''' object '''is.

 

|An '''object '''is an '''instance''' of a class.

 

|Recall the example of '''human being class''' we had discussed in the earlier tutorial.

 

|It exposes its behavior through''' methods'''.

 

 

 

|  Now let us learn about''' reference variables.'''

 

|All other types refer to objects rather than primitives.

 

|Variables that refer to objects are '''reference variables'''.

| Let us go back to the '''Student class''' which we have already created in the earlier''' tutorial'''.

 

|Now'''Save '''the '''file''' by pressing '''Control '''and '''S '''keys simultaneously.

 

|Now create another '''class''' named '''TestStudent '''inside the same''' project.'''

 

|In this '''class '''I have the''' main method.'''

 

|No inside the main''' method '''I will create an''' object '''of the''' Student class.'''

 

|For that, inside the '''main method''', type  

 

|'''Student '''''space''''' stud1''' ''equal to'' '''new''' ''space'' '''Student''' ''opening and closing brackets, semicolon''.

 

|Thus we have created an '''object''' of the '''Student class'''.

 

|Here,''' Student''' is the name of the''' class '''for which the '''object '''is to be created.

 

|'''stud1''' is a '''reference variable''' referring to one '''object '''of the '''Student''' class.

 

|And the''' new keyword''' allocates space for the new '''object''' to be created.

 

|So next line type '''System''' ''dot '''''out''' ''dot '''''println''' within brackets and double quotes '''stud1''' '''contains''' space ''plus '''''stud1''''' ''and then''' '''''semicolon''.

 

|Now, '''save '''and''' run '''the '''file TestStudent''' ''dot''''' java'''.

|So here '''Student '''is the name of the '''class '''of the new '''object '''created.

 

|We can access the '''fields '''and '''methods''' of the '''Student class''' using '''stud1'''.

 

|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.''

 

|Now, let us save and run this file.

| We can see that here '''stud1 '''and '''stud2 '''refers to two different '''objects'''.

 

|That is, '''stud1 '''and '''stud2''' are referring to two different students.

 

|   05:44

| Now, we can make a change here.

 

|Here type '''Student stud2''' ''equal to'' '''stud1.'''

 

|Now, '''save''' and '''run''' this''' file'''.

 

 

 

|   We can see that here both''' stud1''' and '''stud2 '''refers to the same '''object.'''

 

|That means both '''stud1 '''and '''stud2 '''are referring to the same '''student''' with a roll number and name.

| So in this tutorial we learnt about

|Reference variables

| Creating object using new operator  

|And  Assigning references

 

 

| For self assessment  

| create another '''class''' named '''TestEmployee'''.

| Create an '''object '''of the '''Employee class'''  with ''reference variable'' as '''emp1'''.

 

 

| To know more about the spoken tutorial project.

|Watch the video available at [http://spoken-tutorial.org/What_is_a_Spoken_Tutorial http://spoken-][http://spoken-tutorial.org/What_is_a_Spoken_Tutorial tutorial.org/What_is_a_Spoken_Tutorial]

 

| It summarises the Spoken Tutorial project  

| If you do not have good bandwidth, you can download and watch it  

 

 

| | The Spoken Tutorial Project Team

|Conducts workshops using spoken tutorials  

| Gives certificates for those who pass an online test  

|  Spoken Tutorial Project is a part of the Talk to a Teacher project  

|It is supported by the National Mission on Education through ICT, MHRD, Government of India  

| More information on this Mission is available at  

  [http://spoken-tutorial.org/NMEICT-Intro http://spoken-tutorial.org/NMEICT-Intro]

 

 

| Thus we  have come to the end of this tutorial.

|This is Arya Ratish from IIT Bombay signing off.