View source for Java/C2/while-loop/English-timed

 
{| border=1
|| '''Time'''
|| '''Narration'''

|-
|-
| 00:02
| Welcome to the spoken tutorial on '''While Loop''' in java.

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|  00:06
|  In this tutorial, you will learn: * about the '''while loop'''
* how to use it.

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|  00:12
|  For this tutorial, we are using:
'''Ubuntu 11.10''', 
'''JDK 1.6''' and 
'''Eclipse 3.7'''

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|  00:21
|   To follow this tutorial, you must have knowledge of '''relational operators in Java'''. 

|-
|  00:26	 
| If not, for relevant tutorials, please visit our website as shown. [http://spoken-tutorial.org]
 
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|  00:36
| Here is the '''structure''' of a '''while loop'''. 

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|  00:39
| It has two parts.

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|  00:41
| One is the '''loop running condition''' and the  second is the '''loop variable.'''

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|   00:48
|  Let us now look at an example. Switch to '''Eclipse'''.

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|   00:55
| Here, we have the '''eclipse IDE''' and  the skeleton   required  for rest of the code.

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|   01:00
| I have created a '''class WhileDemo''' and added the '''main method''' to it.

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|  01:05
|  | We shall print numbers from '''1''' to '''10''' using a '''while loop'''. Type: '''int n = 1'''.

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| 01:15
|  This variable 'n' is going to be our '''loop variable'''.

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|  01:21
|  Type: '''while''' in parenthesis '''n''' less than or  equal to  '''10'''  open and close braces.

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|  01:33
| This condition is called  '''looping running condition'''.

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|  01:37
| It means the '''loop''' will '''run''' as long as this condition is true.

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|  01:42
| In our case, it will run as long as the value of 'n' is less than or equal to 10.

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|   01:47
| And it will stop only when the value of 'n' becomes greater than 10.

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|   01:53
| Inside the '''loop''', we shall print the value of 'n'.  

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|  01:58
| '''System.out.println(n);''' and then increment '''n = n + 1;'''

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| 02:12
| This way, first 1 is printed and then the value of 'n' becomes 2. 

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|  02:18
| Then the '''loop condition''' is checked.
 
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|  02:21
| Since it is true, 2 is printed and n becomes 3.

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|  02:25
|  And so on.. loop progresses until 10 is printed.  After that 'n' becomes 11 and the condition is not true and the '''loop''' will stop.

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|  02:37
|  So, let us see the code in action.

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|  02:39
|  '''Save''' and  '''run'''.

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|  02:47
| As we can see, the numbers from 1 to 10 are printed.

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|  02:52
| Now we shall  print numbers from '''50''' to '''40'''.

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|  02:58
|  So, we start with 50.   Change '''n = 1''' to '''n = 50'''.

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| 03:03
| And We go till 40.

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|  03:05
| In other words, as long as 'n' is greater than or equal to 40. So, change the condition to  n   greater than or equal to 40.

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| 03:16 
| And since we are looping from a bigger number to a smaller number, we have decremented the loop variable.

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|  03:22
| So Change '''n=n+1''' to '''n=n-1'''.
 
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| 03:27
| '''Save''' and '''run'''. As we can see, the numbers 50 to 40 have been printed.

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|  03:42
| Now we shall print the first 10 multiples of 7.

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|  03:48
|  To do that, we start with 7. 

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|  03:50
| So, change '''n = 50''' to '''n = 7''' and then end with 70.

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|  03:57
| Change the condition to '''n''' less than equal to '''70'''.

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|  04:03
| This way, we make sure the '''loop''' stops at 70.

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|  04:07
| To get the multiples, we shall increment the '''loop variable''' by 7.

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|  04:12
|So, change '''n=n-1''' to '''n= n+7'''.

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|  04:18
|  This way, first 7 is printed and  then 'n' becomes 14, 14 is printed and so on until 70. '''Save''' and '''run'''.

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|  04:33
|  | As we can see, the first 10 multiples of 7 are  printed.

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|  04:43
| We can also use a '''while loop''' to get the sum of digits of a number.

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|  04:47
| Let us see how to do so.

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|  04:49
| First, clear the '''main method'''.

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|  04:54
| '''int n''' equal to '''13876'''. This is the number.

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| 05:02
| Then '''int dSum''' equal to  '''0''' The variable '''dsum''' with symbolic for digit sum will contain the sum of digits.

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|  05:18
|  Type: '''while n''' greater than '''0''' open close parenthesis.

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|  05:27
| The reason for using this condition will be evident in a while.

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|  05:32
| To get the sum of digits, we must first get the digits.
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|  05:36
| To do that, we use '''modulo operator'''. 

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|  05:40
| Type: '''dSum = dSum + (n % 10)''' So, we get the unit digit and add it to '''dsum'''.

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|   05:52
|After that  we remove the digit by dividing by 10. n = n / 10

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| 06:08
| So when the '''loop''' is  '''run'''  for the first time, '''dSum''' will be 6 and 'n' will be 1387.

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| 06:15
| And when the loop is '''run''' for the second time, '''dSum''' will be sum of 7 and 6 which is 13 and 'n' will become 138.

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|   06:22
| So on as the loop progresses, the digits will be  removed from '''n''' and finally

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|  06:28
|  '''n''' becomes zero. After that the condition 'n greater than 0' will be false and the loop will stop.

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| 06:36
| So, let us now add a print statement:
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|  06:42
| '''System.out.println(dSum)'''

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|  06:51
| Let us see the code and action. '''Save''' and '''run'''.
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|  06:59
| As we can see, the sum of digit which is 25 has been printed.
 
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| 07:06 
| This way, a '''while loop''' which is one of the most fundamental '''constructs''' in programming, can be used.

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|   07:16
|  This brings us to the end of the tutorial. 

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|  07:20
| In this tutorial, we have learnt:
* About while loop
* How to use it.

|-
|07:26
| As an assignment for this tutorial, solve the following problem.

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|  07:29
| Given a number, compute its reverse by using a while loop. Example: 19435 => 53491

|-
|07:37
|To know more about the Spoken Tutorial project, watch the video available at the following link, that summarizes the Spoken Tutorial project.

|-
|  07:45
| If you do not have good bandwidth, you can download and watch it.

|-
| 07:50 
|  The Spoken Tutorial Project Team: Conducts workshops using spoken tutorials. Gives certificates for those who pass an online test.

|-
|  07:57
| For more details, please write to '''contact AT spoken HYPHEN tutorial DOT org.'''

|-
| 08:03
| Spoken Tutorial Project is a part of the Talk to a Teacher project.

|-
|  08:07
|  It is supported by the National Mission on Education through ICT, MHRD, Government of India.

|-
|  08:12
| More information on this mission is available at the following link.

|-
|  08:17
|  This tutorial has been contributed by '''TalentSprint'''. Thanks for joining.

|}